调用GetCallerIdentityAsync遇ClientName空值错误，如何指定ClientName？

使用AWS SDK官方文档示例代码尝试扮演IAM角色时，调用GetCallerIdentityAsync方法抛出错误：

Value cannot be null. Parameter name: Options property cannot be empty: ClientName

相关代码示例如下：

using System;
using System.Threading.Tasks;
using Amazon;
using Amazon.SecurityToken;
using Amazon.SecurityToken.Model;

namespace AssumeRoleExample
{
    class AssumeRole
    {
    /// <summary>
    /// This example shows how to use the AWS Security Token
    /// Service (AWS STS) to assume an IAM role.
    ///
    /// NOTE: It is important that the role that will be assumed has a
    /// trust relationship with the account that will assume the role.
    ///
    /// Before you run the example, you need to create the role you want to
    /// assume and have it trust the IAM account that will assume that role.
    /// </summary>

    private static readonly RegionEndpoint REGION = RegionEndpoint.USWest2;

    static async Task Main()
    {
        // Create the SecurityToken client and then display the identity of the
        // default user.
        var roleArnToAssume = "arn:aws:iam::123456789012:role/testAssumeRole";

        var client = new Amazon.SecurityToken.AmazonSecurityTokenServiceClient(REGION);

        // Get and display the information about the identity of the default user.
        var callerIdRequest = new GetCallerIdentityRequest();
        var caller = await client.GetCallerIdentityAsync(callerIdRequest);
        Console.WriteLine($"Original Caller: {caller.Arn}");

        // Create the request to use with the AssumeRoleAsync call.
        var assumeRoleReq = new AssumeRoleRequest()
        {
            DurationSeconds = 1600,
            RoleSessionName = "Session1",
            RoleArn = roleArnToAssume
        };

        var assumeRoleRes = await client.AssumeRoleAsync(assumeRoleReq);

        // Now create a new client based on the credentials of the caller assuming the role.
        var client2 = new AmazonSecurityTokenServiceClient(credentials: assumeRoleRes.Credentials);

        // Get and display information about the caller that has assumed the defined role.
        var caller2 = await client2.GetCallerIdentityAsync(callerIdRequest);
        Console.WriteLine($"AssumedRole Caller: {caller2.Arn}");
    }
}
} 

已通过在线控制台创建IAM用户，并按照文档委托了使用特定服务的对应权限，请问该如何指定ClientName？目前未找到相关公开资料。

这个错误是因为创建第二个AmazonSecurityTokenServiceClient实例时，仅传入凭证但未正确初始化客户端配置，导致ClientName属性缺失。可以通过以下两种方式解决：

• 方式一：显式指定配置选项
  创建客户端时，同时传入凭证、区域并设置自定义ClientName：

  var client2 = new AmazonSecurityTokenServiceClient(
      assumeRoleRes.Credentials,
      new AmazonSecurityTokenServiceConfig
      {
          RegionEndpoint = REGION,
          ClientName = "STSAssumedRoleClient"
      });
  

• 方式二：使用带区域的构造函数
  直接调用同时接收凭证和区域的构造函数，SDK会自动填充必要的配置（包括默认ClientName）：

  var client2 = new AmazonSecurityTokenServiceClient(assumeRoleRes.Credentials, REGION);
  

原代码中创建client2时仅传入凭证参数，未指定区域或配置，导致SDK内部初始化时ClientName为空触发异常。第二种方式更简洁，符合SDK常规使用习惯，优先推荐。

内容的提问来源于stack exchange，提问作者Leventogenna