的版本 4 (V4) 适用于 .NET 的 Amazon SDK 已经发布！

有关重大更改和迁移应用程序的信息，请参阅[迁移主题](https://docs.amazonaws.cn/sdk-for-net/v4/developer-guide/net-dg-v4.html)。

 [https://docs.amazonaws.cn/sdk-for-net/v4/developer-guide/net-dg-v4.html](https://docs.amazonaws.cn/sdk-for-net/v4/developer-guide/net-dg-v4.html)

本文属于机器翻译版本。若本译文内容与英语原文存在差异，则一律以英文原文为准。

# 更新 Amazon SQS 队列
更新队列

此示例向您展示如何使用更新 Amazon SQS 队列。 适用于 .NET 的 Amazon SDK 经过一些检查后，应用程序使用给定值更新给定属性，然后显示队列的所有属性。

如果命令行参数中仅包含队列 URL，则应用程序仅显示队列的所有属性。

以下各节提供了此示例的片段。此后显示了[该示例的完整代码](#UpdateSqsQueue-complete-code)，并且可以按原样构建和运行。

**Topics**
+ [

## 显示队列属性
](#UpdateSqsQueue-show-attributes)
+ [

## 验证属性名称
](#UpdateSqsQueue-validate-attribute)
+ [

## 更新队列属性
](#UpdateSqsQueue-update-attribute)
+ [

## 完整代码
](#UpdateSqsQueue-complete-code)
+ [

## 其他注意事项
](#UpdateSqsQueue-additional)

## 显示队列属性


以下代码片段显示了由给定队列 URL 标识的队列的属性。

[本主题末尾](#UpdateSqsQueue-complete-code)的示例显示了此片段的使用情况。

```
    //
    // 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}");
    }
```

## 验证属性名称


以下代码片段验证了正在更新的属性的名称。

[本主题末尾](#UpdateSqsQueue-complete-code)的示例显示了此片段的使用情况。

```
    //
    // 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;
    }
```

## 更新队列属性


以下代码片段更新了由给定队列 URL 标识的队列属性。

[本主题末尾](#UpdateSqsQueue-complete-code)的示例显示了此片段的使用情况。

```
    //
    // 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}});
    }
```

## 完整代码


本部分显示了本示例的相关参考和完整代码。

### SDK 参考


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

编程元素：
+ 命名空间 [Amazon.SQS](https://docs.amazonaws.cn/sdkfornet/v4/apidocs/items/SQS/NSQS.html)

  [Amazon 上](https://docs.amazonaws.cn/sdkfornet/v4/apidocs/items/SQS/TSQSClient.html)课 SQSClient

  班级 [QueueAttributeName](https://docs.amazonaws.cn/sdkfornet/v4/apidocs/items/SQS/TQueueAttributeName.html)
+ 命名空间 [Amazon.SQS.Model](https://docs.amazonaws.cn/sdkfornet/v4/apidocs/items/SQS/NSQSModel.html)

  班级 [GetQueueAttributesResponse](https://docs.amazonaws.cn/sdkfornet/v4/apidocs/items/SQS/TGetQueueAttributesResponse.html)

### 代码


```
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);
    }
  }

}
```

## 其他注意事项

+ 要更新该`RedrivePolicy`属性，您必须根据自己的操作系统将整个值加上引号并 key/value 对对的引号进行转义。

  例如，在 Windows 上，该值的构造方式类似于以下内容：

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