適用於 .NET 的 AWS SDK V3 已進入維護模式。

我們建議您遷移至 [適用於 .NET 的 AWS SDK V4](https://docs.aws.amazon.com/sdk-for-net/v4/developer-guide/welcome.html)。如需如何遷移的其他詳細資訊和資訊，請參閱我們的[維護模式公告](https://aws.amazon.com/blogs/developer/aws-sdk-for-net-v3-maintenance-mode-announcement/)。

本文為英文版的機器翻譯版本，如內容有任何歧義或不一致之處，概以英文版為準。

# 使用 Amazon SQS 傳送訊息
<a name="sqs-apis-intro"></a>

 適用於 .NET 的 AWS SDK 支援 [Amazon Simple Queue Service (Amazon SQS)](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/)，這是一種訊息佇列服務，可處理系統中元件之間的訊息或工作流程。

Amazon SQS 佇列提供一種機制，可讓您在微型服務、分散式系統和無伺服器應用程式等軟體元件之間傳送、存放和接收訊息。這可讓您解耦這類元件，讓您無需設計和操作自己的簡訊系統。如需有關佇列和訊息如何在 Amazon SQS 中運作的資訊，請參閱[《Amazon Simple Queue Service 開發人員指南》中的 Amazon SQS 教學](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-other-tutorials.html)課程和[基本 Amazon SQS 架構](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-basic-architecture.html)。 [https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/)

**重要**  
由於佇列的分散式性質，Amazon SQS 無法保證您會收到精確的訊息。如果您需要保留訊息順序，請使用 [Amazon SQS FIFO 佇列](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-fifo-queues.html)。

## API
<a name="w2aac19c15c25b9"></a>

為 Amazon SQS 用戶端 適用於 .NET 的 AWS SDK 提供 APIs。APIs 可讓您使用 Amazon SQS 功能，例如佇列和訊息。本節包含一些範例，顯示您在使用這些 APIs 時可遵循的模式。若要檢視完整的 APIs 集，請參閱 [適用於 .NET 的 AWS SDK API 參考](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/) （並捲動至「Amazon.SQS」)。

Amazon SQS APIs 由 [AWSSDK.SQS](https://www.nuget.org/packages/AWSSDK.SQS) NuGet 套件提供。

## 先決條件
<a name="w2aac19c15c25c11"></a>

開始之前，請確定您已[設定環境和專案](net-dg-config.md)。也請檢閱 中的資訊[開發套件功能](net-dg-sdk-features.md)。

## 主題
<a name="w2aac19c15c25c13"></a>

**Topics**
+ [API](#w2aac19c15c25b9)
+ [先決條件](#w2aac19c15c25c11)
+ [主題](#w2aac19c15c25c13)
+ [建立佇列](CreateQueue.md)
+ [更新佇列](UpdateSqsQueue.md)
+ [刪除佇列](DeleteSqsQueue.md)
+ [傳送訊息](SendMessage.md)
+ [接收訊息](ReceiveMessage.md)

# 建立 Amazon SQS 佇列
<a name="CreateQueue"></a>

此範例說明如何使用 適用於 .NET 的 AWS SDK 來建立 Amazon SQS 佇列。如果您未提供無效[字母佇列](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-dead-letter-queues.html)的 ARN，應用程式會建立無效字母佇列。然後，它會建立標準訊息佇列，其中包含無效字母佇列 （您提供的佇列或建立的佇列）。

如果您未提供任何命令列引數，應用程式只會顯示所有現有佇列的相關資訊。

下列各節提供此範例的程式碼片段。之後會顯示[範例的完整程式碼](#CreateQueue-complete-code)，並可依原樣建置和執行。

**Topics**
+ [顯示現有的佇列](#CreateQueue-show-queues)
+ [建立佇列](#CreateQueue-create-queue)
+ [取得佇列的 ARN](#CreateQueue-get-arn)
+ [完成程式碼](#CreateQueue-complete-code)
+ [其他考量](#CreateQueue-additional)

## 顯示現有的佇列
<a name="CreateQueue-show-queues"></a>

下列程式碼片段顯示 SQS 用戶端區域中現有佇列的清單，以及每個佇列的屬性。

[本主題結尾](#CreateQueue-complete-code)的範例顯示此程式碼片段正在使用中。

```
    //
    // Method to show a list of the existing queues
    private static async Task ShowQueues(IAmazonSQS sqsClient)
    {
      ListQueuesResponse responseList = await sqsClient.ListQueuesAsync("");
      Console.WriteLine();
      foreach(string qUrl in responseList.QueueUrls)
      {
        // Get and show all attributes. Could also get a subset.
        await ShowAllAttributes(sqsClient, qUrl);
      }
    }

    //
    // Method to show all attributes of a queue
    private static async Task ShowAllAttributes(IAmazonSQS sqsClient, string qUrl)
    {
      var attributes = new List<string>{ QueueAttributeName.All };
      GetQueueAttributesResponse responseGetAtt =
        await sqsClient.GetQueueAttributesAsync(qUrl, attributes);
      Console.WriteLine($"Queue: {qUrl}");
      foreach(var att in responseGetAtt.Attributes)
        Console.WriteLine($"\t{att.Key}: {att.Value}");
    }
```

## 建立佇列
<a name="CreateQueue-create-queue"></a>

下列程式碼片段會建立佇列。程式碼片段包含使用無效字母佇列，但您的佇列不一定需要無效字母佇列。

[本主題結尾](#CreateQueue-complete-code)的範例顯示此程式碼片段正在使用中。

```
    //
    // Method to create a queue. Returns the queue URL.
    private static async Task<string> CreateQueue(
      IAmazonSQS sqsClient, string qName, string deadLetterQueueUrl=null,
      string maxReceiveCount=null, string receiveWaitTime=null)
    {
      var attrs = new Dictionary<string, string>();

      // If a dead-letter queue is given, create a message queue
      if(!string.IsNullOrEmpty(deadLetterQueueUrl))
      {
        attrs.Add(QueueAttributeName.ReceiveMessageWaitTimeSeconds, receiveWaitTime);
        attrs.Add(QueueAttributeName.RedrivePolicy,
          $"{{\"deadLetterTargetArn\":\"{await GetQueueArn(sqsClient, deadLetterQueueUrl)}\"," +
          $"\"maxReceiveCount\":\"{maxReceiveCount}\"}}");
        // Add other attributes for the message queue such as VisibilityTimeout
      }

      // If no dead-letter queue is given, create one of those instead
      //else
      //{
      //  // Add attributes for the dead-letter queue as needed
      //  attrs.Add();
      //}

      // Create the queue
      CreateQueueResponse responseCreate = await sqsClient.CreateQueueAsync(
          new CreateQueueRequest{QueueName = qName, Attributes = attrs});
      return responseCreate.QueueUrl;
    }
```

## 取得佇列的 ARN
<a name="CreateQueue-get-arn"></a>

下列程式碼片段會取得指定佇列 URL 所識別之佇列的 ARN。

[本主題結尾](#CreateQueue-complete-code)的範例顯示此程式碼片段正在使用中。

```
    //
    // Method to get the ARN of a queue
    private static async Task<string> GetQueueArn(IAmazonSQS sqsClient, string qUrl)
    {
      GetQueueAttributesResponse responseGetAtt = await sqsClient.GetQueueAttributesAsync(
        qUrl, new List<string>{QueueAttributeName.QueueArn});
      return responseGetAtt.QueueARN;
    }
```

## 完成程式碼
<a name="CreateQueue-complete-code"></a>

本節顯示此範例的相關參考和完整程式碼。

### 開發套件參考
<a name="w2aac19c15c25c17c25b5b1"></a>

NuGet 套件：
+ [AWSSDK.SQS](https://www.nuget.org/packages/AWSSDK.SQS)

程式設計元素：
+ 命名空間 [Amazon.SQS](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/NSQS.html)

  [AmazonSQSClient](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TSQSClient.html) 類別

  類別 [QueueAttributeName](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TQueueAttributeName.html)
+ 命名空間 [Amazon.SQS.Model](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/NSQSModel.html)

  類別 [CreateQueueRequest](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TCreateQueueRequest.html)

  類別 [CreateQueueResponse](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TCreateQueueResponse.html)

  類別 [GetQueueAttributesResponse](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TGetQueueAttributesResponse.html)

  類別 [ListQueuesResponse](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TListQueuesResponse.html)

### 程式碼
<a name="w2aac19c15c25c17c25b7b1"></a>

```
using System;
using System.Threading.Tasks;
using System.Collections.Generic;
using Amazon.SQS;
using Amazon.SQS.Model;

namespace SQSCreateQueue
{
  // = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
  // Class to create a queue
  class Program
  {
    private const string MaxReceiveCount = "10";
    private const string ReceiveMessageWaitTime = "2";
    private const int MaxArgs = 3;

    static async Task Main(string[] args)
    {
      // Parse the command line and show help if necessary
      var parsedArgs = CommandLine.Parse(args);
      if(parsedArgs.Count > MaxArgs)
        CommandLine.ErrorExit(
          "\nToo many command-line arguments.\nRun the command with no arguments to see help.");

      // Create the Amazon SQS client
      var sqsClient = new AmazonSQSClient();

      // In the case of no command-line arguments, just show help and the existing queues
      if(parsedArgs.Count == 0)
      {
        PrintHelp();
        Console.WriteLine("\nNo arguments specified.");
        Console.Write("Do you want to see a list of the existing queues? ((y) or n): ");
        string response = Console.ReadLine();
        if((string.IsNullOrEmpty(response)) || (response.ToLower() == "y"))
          await ShowQueues(sqsClient);
        return;
      }

      // Get the application arguments from the parsed list
      string queueName =
        CommandLine.GetArgument(parsedArgs, null, "-q", "--queue-name");
      string deadLetterQueueUrl =
        CommandLine.GetArgument(parsedArgs, null, "-d", "--dead-letter-queue");
      string maxReceiveCount =
        CommandLine.GetArgument(parsedArgs, MaxReceiveCount, "-m", "--max-receive-count");
      string receiveWaitTime =
        CommandLine.GetArgument(parsedArgs, ReceiveMessageWaitTime, "-w", "--wait-time");

      if(string.IsNullOrEmpty(queueName))
        CommandLine.ErrorExit(
          "\nYou must supply a queue name.\nRun the command with no arguments to see help.");

      // If a dead-letter queue wasn't given, create one
      if(string.IsNullOrEmpty(deadLetterQueueUrl))
      {
        Console.WriteLine("\nNo dead-letter queue was specified. Creating one...");
        deadLetterQueueUrl = await CreateQueue(sqsClient, queueName + "__dlq");
        Console.WriteLine($"Your new dead-letter queue:");
        await ShowAllAttributes(sqsClient, deadLetterQueueUrl);
      }

      // Create the message queue
      string messageQueueUrl = await CreateQueue(
        sqsClient, queueName, deadLetterQueueUrl, maxReceiveCount, receiveWaitTime);
      Console.WriteLine($"Your new message queue:");
      await ShowAllAttributes(sqsClient, messageQueueUrl);
    }


    //
    // Method to show a list of the existing queues
    private static async Task ShowQueues(IAmazonSQS sqsClient)
    {
      ListQueuesResponse responseList = await sqsClient.ListQueuesAsync("");
      Console.WriteLine();
      foreach(string qUrl in responseList.QueueUrls)
      {
        // Get and show all attributes. Could also get a subset.
        await ShowAllAttributes(sqsClient, qUrl);
      }
    }


    //
    // Method to create a queue. Returns the queue URL.
    private static async Task<string> CreateQueue(
      IAmazonSQS sqsClient, string qName, string deadLetterQueueUrl=null,
      string maxReceiveCount=null, string receiveWaitTime=null)
    {
      var attrs = new Dictionary<string, string>();

      // If a dead-letter queue is given, create a message queue
      if(!string.IsNullOrEmpty(deadLetterQueueUrl))
      {
        attrs.Add(QueueAttributeName.ReceiveMessageWaitTimeSeconds, receiveWaitTime);
        attrs.Add(QueueAttributeName.RedrivePolicy,
          $"{{\"deadLetterTargetArn\":\"{await GetQueueArn(sqsClient, deadLetterQueueUrl)}\"," +
          $"\"maxReceiveCount\":\"{maxReceiveCount}\"}}");
        // Add other attributes for the message queue such as VisibilityTimeout
      }

      // If no dead-letter queue is given, create one of those instead
      //else
      //{
      //  // Add attributes for the dead-letter queue as needed
      //  attrs.Add();
      //}

      // Create the queue
      CreateQueueResponse responseCreate = await sqsClient.CreateQueueAsync(
          new CreateQueueRequest{QueueName = qName, Attributes = attrs});
      return responseCreate.QueueUrl;
    }


    //
    // Method to get the ARN of a queue
    private static async Task<string> GetQueueArn(IAmazonSQS sqsClient, string qUrl)
    {
      GetQueueAttributesResponse responseGetAtt = await sqsClient.GetQueueAttributesAsync(
        qUrl, new List<string>{QueueAttributeName.QueueArn});
      return responseGetAtt.QueueARN;
    }


    //
    // Method to show all attributes of a queue
    private static async Task ShowAllAttributes(IAmazonSQS sqsClient, string qUrl)
    {
      var attributes = new List<string>{ QueueAttributeName.All };
      GetQueueAttributesResponse responseGetAtt =
        await sqsClient.GetQueueAttributesAsync(qUrl, attributes);
      Console.WriteLine($"Queue: {qUrl}");
      foreach(var att in responseGetAtt.Attributes)
        Console.WriteLine($"\t{att.Key}: {att.Value}");
    }


    //
    // Command-line help
    private static void PrintHelp()
    {
      Console.WriteLine(
      "\nUsage: SQSCreateQueue -q <queue-name> [-d <dead-letter-queue>]" +
        " [-m <max-receive-count>] [-w <wait-time>]" +
      "\n  -q, --queue-name: The name of the queue you want to create." +
      "\n  -d, --dead-letter-queue: The URL of an existing queue to be used as the dead-letter queue."+
      "\n      If this argument isn't supplied, a new dead-letter queue will be created." +
      "\n  -m, --max-receive-count: The value for maxReceiveCount in the RedrivePolicy of the queue." +
      $"\n      Default is {MaxReceiveCount}." +
      "\n  -w, --wait-time: The value for ReceiveMessageWaitTimeSeconds of the queue for long polling." +
      $"\n      Default is {ReceiveMessageWaitTime}.");
    }
  }


  // = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
  // Class that represents a command line on the console or terminal.
  // (This is the same for all examples. When you have seen it once, you can ignore it.)
  static class CommandLine
  {
    //
    // Method to parse a command line of the form: "--key value" or "-k value".
    //
    // Parameters:
    // - args: The command-line arguments passed into the application by the system.
    //
    // Returns:
    // A Dictionary with string Keys and Values.
    //
    // If a key is found without a matching value, Dictionary.Value is set to the key
    //  (including the dashes).
    // If a value is found without a matching key, Dictionary.Key is set to "--NoKeyN",
    //  where "N" represents sequential numbers.
    public static Dictionary<string,string> Parse(string[] args)
    {
      var parsedArgs = new Dictionary<string,string>();
      int i = 0, n = 0;
      while(i < args.Length)
      {
        // If the first argument in this iteration starts with a dash it's an option.
        if(args[i].StartsWith("-"))
        {
          var key = args[i++];
          var value = key;

          // Check to see if there's a value that goes with this option?
          if((i < args.Length) && (!args[i].StartsWith("-"))) value = args[i++];
          parsedArgs.Add(key, value);
        }

        // If the first argument in this iteration doesn't start with a dash, it's a value
        else
        {
          parsedArgs.Add("--NoKey" + n.ToString(), args[i++]);
          n++;
        }
      }

      return parsedArgs;
    }

    //
    // Method to get an argument from the parsed command-line arguments
    //
    // Parameters:
    // - parsedArgs: The Dictionary object returned from the Parse() method (shown above).
    // - defaultValue: The default string to return if the specified key isn't in parsedArgs.
    // - keys: An array of keys to look for in parsedArgs.
    public static string GetArgument(
      Dictionary<string,string> parsedArgs, string defaultReturn, params string[] keys)
    {
      string retval = null;
      foreach(var key in keys)
        if(parsedArgs.TryGetValue(key, out retval)) break;
      return retval ?? defaultReturn;
    }

    //
    // Method to exit the application with an error.
    public static void ErrorExit(string msg, int code=1)
    {
      Console.WriteLine("\nError");
      Console.WriteLine(msg);
      Environment.Exit(code);
    }
  }

}
```

## 其他考量
<a name="CreateQueue-additional"></a>
+ 您的佇列名稱必須由英數字元、連字號和底線組成。
+ 佇列名稱和佇列 URLs 區分大小寫
+ 如果您需要佇列 URL，但只有佇列名稱，請使用其中一種`AmazonSQSClient.GetQueueUrlAsync`方法。
+ 如需有關您可以設定之各種佇列屬性的資訊，請參閱《 [適用於 .NET 的 AWS SDK API 參考](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/)》中的 [CreateQueueRequest](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TCreateQueueRequest.html) 或《[Amazon Simple Queue Service API 參考](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/)》中的 [SetQueueAttributes](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/API_SetQueueAttributes.html)。
+ 此範例會為您建立的佇列上的所有訊息指定長輪詢。這是使用 `ReceiveMessageWaitTimeSeconds` 屬性來完成。

  您也可以在呼叫 [AmazonSQSClient](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TSQSClient.html) 類別`ReceiveMessageAsync`的方法期間指定長輪詢。如需詳細資訊，請參閱[接收 Amazon SQS 訊息](ReceiveMessage.md)。

  如需短輪詢與長輪詢的相關資訊，請參閱《*Amazon Simple Queue Service 開發人員指南*》中的[短輪詢和長輪詢](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-short-and-long-polling.html)。
+ 無效字母佇列是其他 （來源） 佇列可以為未成功處理的訊息設定目標的佇列。如需詳細資訊，請參閱[《Amazon Simple Queue Service 開發人員指南》中的 Amazon SQS 無效字母佇列](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-dead-letter-queues.html)。
+ 您也可以在 [Amazon SQS 主控台](https://console.aws.amazon.com/sqs)中查看佇列清單和此範例的結果。

# 更新 Amazon SQS 佇列
<a name="UpdateSqsQueue"></a>

此範例說明如何使用 適用於 .NET 的 AWS SDK 來更新 Amazon SQS 佇列。經過一些檢查後，應用程式會使用指定的值更新指定的屬性，然後顯示佇列的所有屬性。

如果命令列引數中只包含佇列 URL，則應用程式只會顯示佇列的所有屬性。

下列各節提供此範例的程式碼片段。之後會顯示[範例的完整程式碼](#UpdateSqsQueue-complete-code)，並可依原樣建置和執行。

**Topics**
+ [顯示佇列屬性](#UpdateSqsQueue-show-attributes)
+ [驗證屬性名稱](#UpdateSqsQueue-validate-attribute)
+ [更新佇列屬性](#UpdateSqsQueue-update-attribute)
+ [完成程式碼](#UpdateSqsQueue-complete-code)
+ [其他考量](#UpdateSqsQueue-additional)

## 顯示佇列屬性
<a name="UpdateSqsQueue-show-attributes"></a>

下列程式碼片段顯示指定佇列 URL 所識別之佇列的屬性。

[本主題結尾](#UpdateSqsQueue-complete-code)的範例顯示此程式碼片段正在使用中。

```
    //
    // Method to show all attributes of a queue
    private static async Task ShowAllAttributes(IAmazonSQS sqsClient, string qUrl)
    {
      GetQueueAttributesResponse responseGetAtt =
        await sqsClient.GetQueueAttributesAsync(qUrl,
          new List<string>{ QueueAttributeName.All });
      Console.WriteLine($"Queue: {qUrl}");
      foreach(var att in responseGetAtt.Attributes)
        Console.WriteLine($"\t{att.Key}: {att.Value}");
    }
```

## 驗證屬性名稱
<a name="UpdateSqsQueue-validate-attribute"></a>

下列程式碼片段會驗證要更新的屬性名稱。

[本主題結尾](#UpdateSqsQueue-complete-code)的範例顯示此程式碼片段正在使用中。

```
    //
    // Method to check the name of the attribute
    private static bool ValidAttribute(string attribute)
    {
      var attOk = false;
      var qAttNameType = typeof(QueueAttributeName);
      List<string> qAttNamefields = new List<string>();
      foreach(var field in qAttNameType.GetFields())
       qAttNamefields.Add(field.Name);
      foreach(var name in qAttNamefields)
        if(attribute == name) { attOk = true; break; }
      return attOk;
    }
```

## 更新佇列屬性
<a name="UpdateSqsQueue-update-attribute"></a>

下列程式碼片段會更新指定佇列 URL 所識別之佇列的屬性。

[本主題結尾](#UpdateSqsQueue-complete-code)的範例顯示此程式碼片段正在使用中。

```
    //
    // Method to update a queue attribute
    private static async Task UpdateAttribute(
      IAmazonSQS sqsClient, string qUrl, string attribute, string value)
    {
      await sqsClient.SetQueueAttributesAsync(qUrl,
        new Dictionary<string, string>{{attribute, value}});
    }
```

## 完成程式碼
<a name="UpdateSqsQueue-complete-code"></a>

本節顯示此範例的相關參考和完整程式碼。

### 開發套件參考
<a name="w2aac19c15c25c19c25b5b1"></a>

NuGet 套件：
+ [AWSSDK.SQS](https://www.nuget.org/packages/AWSSDK.SQS)

程式設計元素：
+ 命名空間 [Amazon.SQS](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/NSQS.html)

  [AmazonSQSClient](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TSQSClient.html) 類別

  類別 [QueueAttributeName](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TQueueAttributeName.html)
+ 命名空間 [Amazon.SQS.Model](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/NSQSModel.html)

  類別 [GetQueueAttributesResponse](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TGetQueueAttributesResponse.html)

### 程式碼
<a name="w2aac19c15c25c19c25b7b1"></a>

```
using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Amazon.SQS;
using Amazon.SQS.Model;

namespace SQSUpdateQueue
{
  // = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
  // Class to update a queue
  class Program
  {
    private const int MaxArgs = 3;
    private const int InvalidArgCount = 2;

    static async Task Main(string[] args)
    {
      // Parse the command line and show help if necessary
      var parsedArgs = CommandLine.Parse(args);
      if(parsedArgs.Count == 0)
      {
        PrintHelp();
        return;
      }
      if((parsedArgs.Count > MaxArgs) || (parsedArgs.Count == InvalidArgCount))
        CommandLine.ErrorExit("\nThe number of command-line arguments is incorrect." +
          "\nRun the command with no arguments to see help.");

      // Get the application arguments from the parsed list
      var qUrl = CommandLine.GetArgument(parsedArgs, null, "-q");
      var attribute = CommandLine.GetArgument(parsedArgs, null, "-a");
      var value = CommandLine.GetArgument(parsedArgs, null, "-v", "--value");

      if(string.IsNullOrEmpty(qUrl))
        CommandLine.ErrorExit("\nYou must supply at least a queue URL." +
          "\nRun the command with no arguments to see help.");

      // Create the Amazon SQS client
      var sqsClient = new AmazonSQSClient();

      // In the case of one command-line argument, just show the attributes for the queue
      if(parsedArgs.Count == 1)
        await ShowAllAttributes(sqsClient, qUrl);

      // Otherwise, attempt to update the given queue attribute with the given value
      else
      {
        // Check to see if the attribute is valid
        if(ValidAttribute(attribute))
        {
          // Perform the update and then show all the attributes of the queue
          await UpdateAttribute(sqsClient, qUrl, attribute, value);
          await ShowAllAttributes(sqsClient, qUrl);
        }
        else
        {
          Console.WriteLine($"\nThe given attribute name, {attribute}, isn't valid.");
        }
      }
    }


    //
    // Method to show all attributes of a queue
    private static async Task ShowAllAttributes(IAmazonSQS sqsClient, string qUrl)
    {
      GetQueueAttributesResponse responseGetAtt =
        await sqsClient.GetQueueAttributesAsync(qUrl,
          new List<string>{ QueueAttributeName.All });
      Console.WriteLine($"Queue: {qUrl}");
      foreach(var att in responseGetAtt.Attributes)
        Console.WriteLine($"\t{att.Key}: {att.Value}");
    }


    //
    // Method to check the name of the attribute
    private static bool ValidAttribute(string attribute)
    {
      var attOk = false;
      var qAttNameType = typeof(QueueAttributeName);
      List<string> qAttNamefields = new List<string>();
      foreach(var field in qAttNameType.GetFields())
       qAttNamefields.Add(field.Name);
      foreach(var name in qAttNamefields)
        if(attribute == name) { attOk = true; break; }
      return attOk;
    }


    //
    // Method to update a queue attribute
    private static async Task UpdateAttribute(
      IAmazonSQS sqsClient, string qUrl, string attribute, string value)
    {
      await sqsClient.SetQueueAttributesAsync(qUrl,
        new Dictionary<string, string>{{attribute, value}});
    }


    //
    // Command-line help
    private static void PrintHelp()
    {
      Console.WriteLine("\nUsage: SQSUpdateQueue -q queue_url [-a attribute -v value]");
      Console.WriteLine("  -q: The URL of the queue you want to update.");
      Console.WriteLine("  -a: The name of the attribute to update.");
      Console.WriteLine("  -v, --value: The value to assign to the attribute.");
    }
  }


  // = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
  // Class that represents a command line on the console or terminal.
  // (This is the same for all examples. When you have seen it once, you can ignore it.)
  static class CommandLine
  {
    //
    // Method to parse a command line of the form: "--key value" or "-k value".
    //
    // Parameters:
    // - args: The command-line arguments passed into the application by the system.
    //
    // Returns:
    // A Dictionary with string Keys and Values.
    //
    // If a key is found without a matching value, Dictionary.Value is set to the key
    //  (including the dashes).
    // If a value is found without a matching key, Dictionary.Key is set to "--NoKeyN",
    //  where "N" represents sequential numbers.
    public static Dictionary<string,string> Parse(string[] args)
    {
      var parsedArgs = new Dictionary<string,string>();
      int i = 0, n = 0;
      while(i < args.Length)
      {
        // If the first argument in this iteration starts with a dash it's an option.
        if(args[i].StartsWith("-"))
        {
          var key = args[i++];
          var value = key;

          // Check to see if there's a value that goes with this option?
          if((i < args.Length) && (!args[i].StartsWith("-"))) value = args[i++];
          parsedArgs.Add(key, value);
        }

        // If the first argument in this iteration doesn't start with a dash, it's a value
        else
        {
          parsedArgs.Add("--NoKey" + n.ToString(), args[i++]);
          n++;
        }
      }

      return parsedArgs;
    }

    //
    // Method to get an argument from the parsed command-line arguments
    //
    // Parameters:
    // - parsedArgs: The Dictionary object returned from the Parse() method (shown above).
    // - defaultValue: The default string to return if the specified key isn't in parsedArgs.
    // - keys: An array of keys to look for in parsedArgs.
    public static string GetArgument(
      Dictionary<string,string> parsedArgs, string defaultReturn, params string[] keys)
    {
      string retval = null;
      foreach(var key in keys)
        if(parsedArgs.TryGetValue(key, out retval)) break;
      return retval ?? defaultReturn;
    }

    //
    // Method to exit the application with an error.
    public static void ErrorExit(string msg, int code=1)
    {
      Console.WriteLine("\nError");
      Console.WriteLine(msg);
      Environment.Exit(code);
    }
  }

}
```

## 其他考量
<a name="UpdateSqsQueue-additional"></a>
+ 若要更新 `RedrivePolicy` 屬性，您必須根據您的作業系統，引用整個值並逸出鍵/值對的引號。

  例如，在 Windows 上， 值的建構方式類似如下：

  ```
  "{\"deadLetterTargetArn\":\"DEAD_LETTER-QUEUE-ARN\",\"maxReceiveCount\":\"10\"}"
  ```

# 刪除 Amazon SQS 佇列
<a name="DeleteSqsQueue"></a>

此範例說明如何使用 適用於 .NET 的 AWS SDK 刪除 Amazon SQS 佇列。應用程式會刪除佇列、等待一段指定的時間讓佇列消失，然後顯示剩餘的佇列清單。

如果您未提供任何命令列引數，應用程式只會顯示現有佇列的清單。

下列各節提供此範例的程式碼片段。之後會顯示[範例的完整程式碼](#DeleteSqsQueue-complete-code)，並可依原樣建置和執行。

**Topics**
+ [刪除佇列](#DeleteSqsQueue-delete-queue)
+ [等待佇列消失](#DeleteSqsQueue-wait)
+ [顯示現有佇列的清單](#DeleteSqsQueue-list-queues)
+ [完成程式碼](#DeleteSqsQueue-complete-code)
+ [其他考量](#DeleteSqsQueue-additional)

## 刪除佇列
<a name="DeleteSqsQueue-delete-queue"></a>

下列程式碼片段會刪除指定佇列 URL 所識別的佇列。

[本主題結尾](#DeleteSqsQueue-complete-code)的範例顯示此程式碼片段正在使用中。

```
    //
    // Method to delete an SQS queue
    private static async Task DeleteQueue(IAmazonSQS sqsClient, string qUrl)
    {
      Console.WriteLine($"Deleting queue {qUrl}...");
      await sqsClient.DeleteQueueAsync(qUrl);
      Console.WriteLine($"Queue {qUrl} has been deleted.");
    }
```

## 等待佇列消失
<a name="DeleteSqsQueue-wait"></a>

下列程式碼片段會等待刪除程序完成，這可能需要 60 秒。

[本主題結尾](#DeleteSqsQueue-complete-code)的範例顯示此程式碼片段正在使用中。

```
    //
    // Method to wait up to a given number of seconds
    private static async Task Wait(
      IAmazonSQS sqsClient, int numSeconds, string qUrl)
    {
      Console.WriteLine($"Waiting for up to {numSeconds} seconds.");
      Console.WriteLine("Press any key to stop waiting. (Response might be slightly delayed.)");
      for(int i=0; i<numSeconds; i++)
      {
        Console.Write(".");
        Thread.Sleep(1000);
        if(Console.KeyAvailable) break;

        // Check to see if the queue is gone yet
        var found = false;
        ListQueuesResponse responseList = await sqsClient.ListQueuesAsync("");
        foreach(var url in responseList.QueueUrls)
        {
          if(url == qUrl)
          {
            found = true;
            break;
          }
        }
        if(!found) break;
      }
    }
```

## 顯示現有佇列的清單
<a name="DeleteSqsQueue-list-queues"></a>

下列程式碼片段顯示 SQS 用戶端區域中現有佇列的清單。

[本主題結尾](#DeleteSqsQueue-complete-code)的範例顯示此程式碼片段正在使用中。

```
    //
    // Method to show a list of the existing queues
    private static async Task ListQueues(IAmazonSQS sqsClient)
    {
      ListQueuesResponse responseList = await sqsClient.ListQueuesAsync("");
      Console.WriteLine("\nList of queues:");
      foreach(var qUrl in responseList.QueueUrls)
        Console.WriteLine($"- {qUrl}");
    }
```

## 完成程式碼
<a name="DeleteSqsQueue-complete-code"></a>

本節顯示此範例的相關參考和完整程式碼。

### 開發套件參考
<a name="w2aac19c15c25c21c25b5b1"></a>

NuGet 套件：
+ [AWSSDK.SQS](https://www.nuget.org/packages/AWSSDK.SQS)

程式設計元素：
+ 命名空間 [Amazon.SQS](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/NSQS.html)

  [AmazonSQSClient](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TSQSClient.html) 類別
+ 命名空間 [Amazon.SQS.Model](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/NSQSModel.html)

  類別 [ListQueuesResponse](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TListQueuesResponse.html)

### 程式碼
<a name="w2aac19c15c25c21c25b7b1"></a>

```
using System;
using System.Threading;
using System.Threading.Tasks;
using Amazon.SQS;
using Amazon.SQS.Model;

namespace SQSDeleteQueue
{
  // = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
  // Class to update a queue
  class Program
  {
    private const int TimeToWait = 60;

    static async Task Main(string[] args)
    {
      // Create the Amazon SQS client
      var sqsClient = new AmazonSQSClient();

      // If no command-line arguments, just show a list of the queues
      if(args.Length == 0)
      {
        Console.WriteLine("\nUsage: SQSCreateQueue queue_url");
        Console.WriteLine("   queue_url - The URL of the queue you want to delete.");
        Console.WriteLine("\nNo arguments specified.");
        Console.Write("Do you want to see a list of the existing queues? ((y) or n): ");
        var response = Console.ReadLine();
        if((string.IsNullOrEmpty(response)) || (response.ToLower() == "y"))
          await ListQueues(sqsClient);
        return;
      }

      // If given a queue URL, delete that queue
      if(args[0].StartsWith("https://sqs."))
      {
        // Delete the queue
        await DeleteQueue(sqsClient, args[0]);
        // Wait for a little while because it takes a while for the queue to disappear
        await Wait(sqsClient, TimeToWait, args[0]);
        // Show a list of the remaining queues
        await ListQueues(sqsClient);
      }
      else
      {
        Console.WriteLine("The command-line argument isn't a queue URL:");
        Console.WriteLine($"{args[0]}");
      }
    }


    //
    // Method to delete an SQS queue
    private static async Task DeleteQueue(IAmazonSQS sqsClient, string qUrl)
    {
      Console.WriteLine($"Deleting queue {qUrl}...");
      await sqsClient.DeleteQueueAsync(qUrl);
      Console.WriteLine($"Queue {qUrl} has been deleted.");
    }


    //
    // Method to wait up to a given number of seconds
    private static async Task Wait(
      IAmazonSQS sqsClient, int numSeconds, string qUrl)
    {
      Console.WriteLine($"Waiting for up to {numSeconds} seconds.");
      Console.WriteLine("Press any key to stop waiting. (Response might be slightly delayed.)");
      for(int i=0; i<numSeconds; i++)
      {
        Console.Write(".");
        Thread.Sleep(1000);
        if(Console.KeyAvailable) break;

        // Check to see if the queue is gone yet
        var found = false;
        ListQueuesResponse responseList = await sqsClient.ListQueuesAsync("");
        foreach(var url in responseList.QueueUrls)
        {
          if(url == qUrl)
          {
            found = true;
            break;
          }
        }
        if(!found) break;
      }
    }


    //
    // Method to show a list of the existing queues
    private static async Task ListQueues(IAmazonSQS sqsClient)
    {
      ListQueuesResponse responseList = await sqsClient.ListQueuesAsync("");
      Console.WriteLine("\nList of queues:");
      foreach(var qUrl in responseList.QueueUrls)
        Console.WriteLine($"- {qUrl}");
    }
  }
}
```

## 其他考量
<a name="DeleteSqsQueue-additional"></a>
+ `DeleteQueueAsync` API 呼叫不會檢查您要刪除的佇列是否用作無效字母佇列。更複雜的程序可以檢查此項目。
+ 您也可以在 [Amazon SQS 主控台](https://console.aws.amazon.com/sqs)中查看佇列清單和此範例的結果。

# 傳送 Amazon SQS 訊息
<a name="SendMessage"></a>

此範例說明如何使用 適用於 .NET 的 AWS SDK 將訊息傳送至 Amazon SQS 佇列，您可以透過[程式設計方式](CreateQueue.md)或使用 [Amazon SQS 主控台](https://console.aws.amazon.com/sqs)建立該佇列。應用程式會將單一訊息傳送至佇列，然後傳送一批訊息。然後，應用程式會等待使用者輸入，這可以是要傳送至佇列的其他訊息或結束應用程式的請求。

此範例和[接收訊息的下一個範例](ReceiveMessage.md)可以一起使用，以查看 Amazon SQS 中的訊息流程。

下列各節提供此範例的程式碼片段。之後會顯示[範例的完整程式碼](#SendMessage-complete-code)，並可依原樣建置和執行。

**Topics**
+ [傳送訊息](#SendMessage-send-message)
+ [傳送一批訊息](#SendMessage-send-batch)
+ [從佇列刪除所有訊息](#SendMessage-purge-messages)
+ [完成程式碼](#SendMessage-complete-code)
+ [其他考量](#SendMessage-additional)

## 傳送訊息
<a name="SendMessage-send-message"></a>

下列程式碼片段會傳送訊息至指定佇列 URL 所識別的佇列。

[本主題結尾](#SendMessage-complete-code)的範例顯示此程式碼片段正在使用中。

```
    //
    // Method to put a message on a queue
    // Could be expanded to include message attributes, etc., in a SendMessageRequest
    private static async Task SendMessage(
      IAmazonSQS sqsClient, string qUrl, string messageBody)
    {
      SendMessageResponse responseSendMsg =
        await sqsClient.SendMessageAsync(qUrl, messageBody);
      Console.WriteLine($"Message added to queue\n  {qUrl}");
      Console.WriteLine($"HttpStatusCode: {responseSendMsg.HttpStatusCode}");
    }
```

## 傳送一批訊息
<a name="SendMessage-send-batch"></a>

下列程式碼片段會將一批訊息傳送至指定佇列 URL 所識別的佇列。

[本主題結尾](#SendMessage-complete-code)的範例顯示此程式碼片段正在使用中。

```
    //
    // Method to put a batch of messages on a queue
    // Could be expanded to include message attributes, etc.,
    // in the SendMessageBatchRequestEntry objects
    private static async Task SendMessageBatch(
      IAmazonSQS sqsClient, string qUrl, List<SendMessageBatchRequestEntry> messages)
    {
      Console.WriteLine($"\nSending a batch of messages to queue\n  {qUrl}");
      SendMessageBatchResponse responseSendBatch =
        await sqsClient.SendMessageBatchAsync(qUrl, messages);
      // Could test responseSendBatch.Failed here
      foreach(SendMessageBatchResultEntry entry in responseSendBatch.Successful)
        Console.WriteLine($"Message {entry.Id} successfully queued.");
    }
```

## 從佇列刪除所有訊息
<a name="SendMessage-purge-messages"></a>

下列程式碼片段會從指定佇列 URL 識別的佇列中刪除所有訊息。這也稱為*清除佇列*。

[本主題結尾](#SendMessage-complete-code)的範例顯示此程式碼片段正在使用中。

```
    //
    // Method to delete all messages from the queue
    private static async Task DeleteAllMessages(IAmazonSQS sqsClient, string qUrl)
    {
      Console.WriteLine($"\nPurging messages from queue\n  {qUrl}...");
      PurgeQueueResponse responsePurge = await sqsClient.PurgeQueueAsync(qUrl);
      Console.WriteLine($"HttpStatusCode: {responsePurge.HttpStatusCode}");
    }
```

## 完成程式碼
<a name="SendMessage-complete-code"></a>

本節顯示此範例的相關參考和完整程式碼。

### 開發套件參考
<a name="w2aac19c15c25c23c25b5b1"></a>

NuGet 套件：
+ [AWSSDK.SQS](https://www.nuget.org/packages/AWSSDK.SQS)

程式設計元素：
+ 命名空間 [Amazon.SQS](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/NSQS.html)

  [AmazonSQSClient](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TSQSClient.html) 類別
+ 命名空間 [Amazon.SQS.Model](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/NSQSModel.html)

  類別 [PurgeQueueResponse](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TPurgeQueueResponse.html)

  類別 [SendMessageBatchResponse](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TSendMessageBatchResponse.html)

  類別 [SendMessageResponse](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TSendMessageResponse.html)

  類別 [SendMessageBatchRequestEntry](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TSendMessageBatchRequestEntry.html)

  類別 [SendMessageBatchResultEntry](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TSendMessageBatchResultEntry.html)

### 程式碼
<a name="w2aac19c15c25c23c25b7b1"></a>

```
using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Amazon.SQS;
using Amazon.SQS.Model;

namespace SQSSendMessages
{
  // = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
  // Class to send messages to a queue
  class Program
  {
    // Some example messages to send to the queue
    private const string JsonMessage = "{\"product\":[{\"name\":\"Product A\",\"price\": \"32\"},{\"name\": \"Product B\",\"price\": \"27\"}]}";
    private const string XmlMessage = "<products><product name=\"Product A\" price=\"32\" /><product name=\"Product B\" price=\"27\" /></products>";
    private const string CustomMessage = "||product|Product A|32||product|Product B|27||";
    private const string TextMessage = "Just a plain text message.";

    static async Task Main(string[] args)
    {
      // Do some checks on the command-line
      if(args.Length == 0)
      {
        Console.WriteLine("\nUsage: SQSSendMessages queue_url");
        Console.WriteLine("   queue_url - The URL of an existing SQS queue.");
        return;
      }
      if(!args[0].StartsWith("https://sqs."))
      {
        Console.WriteLine("\nThe command-line argument isn't a queue URL:");
        Console.WriteLine($"{args[0]}");
        return;
      }

      // Create the Amazon SQS client
      var sqsClient = new AmazonSQSClient();

      // (could verify that the queue exists)
      // Send some example messages to the given queue
      // A single message
      await SendMessage(sqsClient, args[0], JsonMessage);

      // A batch of messages
      var batchMessages = new List<SendMessageBatchRequestEntry>{
        new SendMessageBatchRequestEntry("xmlMsg", XmlMessage),
        new SendMessageBatchRequestEntry("customeMsg", CustomMessage),
        new SendMessageBatchRequestEntry("textMsg", TextMessage)};
      await SendMessageBatch(sqsClient, args[0], batchMessages);

      // Let the user send their own messages or quit
      await InteractWithUser(sqsClient, args[0]);

      // Delete all messages that are still in the queue
      await DeleteAllMessages(sqsClient, args[0]);
    }


    //
    // Method to put a message on a queue
    // Could be expanded to include message attributes, etc., in a SendMessageRequest
    private static async Task SendMessage(
      IAmazonSQS sqsClient, string qUrl, string messageBody)
    {
      SendMessageResponse responseSendMsg =
        await sqsClient.SendMessageAsync(qUrl, messageBody);
      Console.WriteLine($"Message added to queue\n  {qUrl}");
      Console.WriteLine($"HttpStatusCode: {responseSendMsg.HttpStatusCode}");
    }


    //
    // Method to put a batch of messages on a queue
    // Could be expanded to include message attributes, etc.,
    // in the SendMessageBatchRequestEntry objects
    private static async Task SendMessageBatch(
      IAmazonSQS sqsClient, string qUrl, List<SendMessageBatchRequestEntry> messages)
    {
      Console.WriteLine($"\nSending a batch of messages to queue\n  {qUrl}");
      SendMessageBatchResponse responseSendBatch =
        await sqsClient.SendMessageBatchAsync(qUrl, messages);
      // Could test responseSendBatch.Failed here
      foreach(SendMessageBatchResultEntry entry in responseSendBatch.Successful)
        Console.WriteLine($"Message {entry.Id} successfully queued.");
    }


    //
    // Method to get input from the user
    // They can provide messages to put in the queue or exit the application
    private static async Task InteractWithUser(IAmazonSQS sqsClient, string qUrl)
    {
      string response;
      while (true)
      {
        // Get the user's input
        Console.WriteLine("\nType a message for the queue or \"exit\" to quit:");
        response = Console.ReadLine();
        if(response.ToLower() == "exit") break;

        // Put the user's message in the queue
        await SendMessage(sqsClient, qUrl, response);
      }
    }


    //
    // Method to delete all messages from the queue
    private static async Task DeleteAllMessages(IAmazonSQS sqsClient, string qUrl)
    {
      Console.WriteLine($"\nPurging messages from queue\n  {qUrl}...");
      PurgeQueueResponse responsePurge = await sqsClient.PurgeQueueAsync(qUrl);
      Console.WriteLine($"HttpStatusCode: {responsePurge.HttpStatusCode}");
    }
  }
}
```

## 其他考量
<a name="SendMessage-additional"></a>
+ 如需有關訊息各種限制的資訊，包括允許的字元，請參閱《[Amazon Simple Queue Service 開發人員指南](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/)》中的[訊息相關配額](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-quotas.html#quotas-messages)。
+ 訊息會保留在佇列中，直到刪除或清除佇列為止。當應用程式收到訊息時，即使佇列中仍有訊息，它也不會出現在佇列中。如需可見性逾時的詳細資訊，請參閱 [Amazon SQS 可見性逾時](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/AboutVT.html)。
+ 除了訊息內文之外，您也可以將屬性新增至訊息。如需詳細資訊，請參閱[訊息中繼資料](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-message-metadata.html)。

# 接收 Amazon SQS 訊息
<a name="ReceiveMessage"></a>

此範例說明如何使用 從 Amazon SQS 佇列 適用於 .NET 的 AWS SDK 接收訊息，您可以透過[程式設計方式](CreateQueue.md)或使用 [Amazon SQS 主控台](https://console.aws.amazon.com/sqs)建立。應用程式會從佇列讀取單一訊息、處理訊息 （在此情況下， 會在主控台上顯示訊息內文），然後從佇列刪除訊息。應用程式會重複這些步驟，直到使用者在鍵盤上輸入金鑰為止。

此範例和[先前有關傳送訊息的範例](SendMessage.md)可以一起使用，以查看 Amazon SQS 中的訊息流程。

下列各節提供此範例的程式碼片段。之後會顯示[範例的完整程式碼](#ReceiveMessage-complete-code)，並可依原樣建置和執行。

**Topics**
+ [接收訊息](#ReceiveMessage-receive)
+ [刪除訊息](#ReceiveMessage-delete)
+ [完成程式碼](#ReceiveMessage-complete-code)
+ [其他考量](#ReceiveMessage-additional)

## 接收訊息
<a name="ReceiveMessage-receive"></a>

下列程式碼片段會從指定佇列 URL 識別的佇列接收訊息。

[本主題結尾](#ReceiveMessage-complete-code)的範例顯示此程式碼片段正在使用中。

```
    //
    // Method to read a message from the given queue
    // In this example, it gets one message at a time
    private static async Task<ReceiveMessageResponse> GetMessage(
      IAmazonSQS sqsClient, string qUrl, int waitTime=0)
    {
      return await sqsClient.ReceiveMessageAsync(new ReceiveMessageRequest{
        QueueUrl=qUrl,
        MaxNumberOfMessages=MaxMessages,
        WaitTimeSeconds=waitTime
        // (Could also request attributes, set visibility timeout, etc.)
      });
    }
```

## 刪除訊息
<a name="ReceiveMessage-delete"></a>

下列程式碼片段會從指定佇列 URL 識別的佇列中刪除訊息。

[本主題結尾](#ReceiveMessage-complete-code)的範例顯示此程式碼片段正在使用中。

```
    //
    // Method to delete a message from a queue
    private static async Task DeleteMessage(
      IAmazonSQS sqsClient, Message message, string qUrl)
    {
      Console.WriteLine($"\nDeleting message {message.MessageId} from queue...");
      await sqsClient.DeleteMessageAsync(qUrl, message.ReceiptHandle);
    }
```

## 完成程式碼
<a name="ReceiveMessage-complete-code"></a>

本節顯示此範例的相關參考和完整程式碼。

### 開發套件參考
<a name="w2aac19c15c25c25c21b5b1"></a>

NuGet 套件：
+ [AWSSDK.SQS](https://www.nuget.org/packages/AWSSDK.SQS)

程式設計元素：
+ 命名空間 [Amazon.SQS](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/NSQS.html)

  [AmazonSQSClient](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TSQSClient.html) 類別
+ 命名空間 [Amazon.SQS.Model](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/NSQSModel.html)

  類別 [ReceiveMessageRequest](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TReceiveMessageRequest.html)

  類別 [ReceiveMessageResponse](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TReceiveMessageResponse.html)

### 程式碼
<a name="w2aac19c15c25c25c21b7b1"></a>

```
using System;
using System.Threading.Tasks;
using Amazon.SQS;
using Amazon.SQS.Model;

namespace SQSReceiveMessages
{
  class Program
  {
    private const int MaxMessages = 1;
    private const int WaitTime = 2;
    static async Task Main(string[] args)
    {
      // Do some checks on the command-line
      if(args.Length == 0)
      {
        Console.WriteLine("\nUsage: SQSReceiveMessages queue_url");
        Console.WriteLine("   queue_url - The URL of an existing SQS queue.");
        return;
      }
      if(!args[0].StartsWith("https://sqs."))
      {
        Console.WriteLine("\nThe command-line argument isn't a queue URL:");
        Console.WriteLine($"{args[0]}");
        return;
      }

      // Create the Amazon SQS client
      var sqsClient = new AmazonSQSClient();

      // (could verify that the queue exists)
      // Read messages from the queue and perform appropriate actions
      Console.WriteLine($"Reading messages from queue\n  {args[0]}");
      Console.WriteLine("Press any key to stop. (Response might be slightly delayed.)");
      do
      {
        var msg = await GetMessage(sqsClient, args[0], WaitTime);
        if(msg.Messages.Count != 0)
        {
          if(ProcessMessage(msg.Messages[0]))
            await DeleteMessage(sqsClient, msg.Messages[0], args[0]);
        }
      } while(!Console.KeyAvailable);
    }


    //
    // Method to read a message from the given queue
    // In this example, it gets one message at a time
    private static async Task<ReceiveMessageResponse> GetMessage(
      IAmazonSQS sqsClient, string qUrl, int waitTime=0)
    {
      return await sqsClient.ReceiveMessageAsync(new ReceiveMessageRequest{
        QueueUrl=qUrl,
        MaxNumberOfMessages=MaxMessages,
        WaitTimeSeconds=waitTime
        // (Could also request attributes, set visibility timeout, etc.)
      });
    }


    //
    // Method to process a message
    // In this example, it simply prints the message
    private static bool ProcessMessage(Message message)
    {
      Console.WriteLine($"\nMessage body of {message.MessageId}:");
      Console.WriteLine($"{message.Body}");
      return true;
    }


    //
    // Method to delete a message from a queue
    private static async Task DeleteMessage(
      IAmazonSQS sqsClient, Message message, string qUrl)
    {
      Console.WriteLine($"\nDeleting message {message.MessageId} from queue...");
      await sqsClient.DeleteMessageAsync(qUrl, message.ReceiptHandle);
    }
  }
}
```

## 其他考量
<a name="ReceiveMessage-additional"></a>
+ 若要指定長輪詢，此範例會針對 `ReceiveMessageAsync`方法的每個呼叫使用 `WaitTimeSeconds` 屬性。

  您也可以在[建立](CreateQueue.md)或[更新](UpdateSqsQueue.md)佇列時使用 `ReceiveMessageWaitTimeSeconds` 屬性，為佇列上的所有訊息指定長輪詢。

  如需短輪詢與長輪詢的相關資訊，請參閱《*Amazon Simple Queue Service 開發人員指南*》中的[短輪詢和長輪詢](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-short-and-long-polling.html)。
+ 在訊息處理期間，您可以使用接收控點來變更訊息可見性逾時。如需如何執行此操作的詳細資訊，請參閱 [AmazonSQSClient](https://docs.aws.amazon.com/sdkfornet/v3/apidocs/items/SQS/TSQSClient.html) 類別`ChangeMessageVisibilityAsync`的方法。
+ 無論可見性逾時設定為何，無條件呼叫 `DeleteMessageAsync`方法都會從佇列中移除訊息。