使用Dapr 客户端 处理服务调用，需要遵循的他的模式，通常代码是这个样子的：

var client = DaprClient.CreateInvokeHttpClient(appId: "routing");
var response = await client.GetAsJsonAsync($"/accounts/{17}", cancellationToken);
var account = await response.Content.ReadFromJsonAsync<Account>(cancellationToken: cancellationToken);

我更希望是这样子调用:

public interface IBank
{
            [HttpGet(“/accounts/{accountId}”)]
            Task<Account> GetUser(string accountId, CancellationToken cancellationToken = default);

           [HttpPost(“/deposit”)]
            Task<Account> Deposit([JsonContent] Transaction transaction, CancellationToken cancellationToken = default);

           [HttpPost(“/withdraw”)]
            [RawReturn(Enable =true, EnsureSuccessStatusCode = false)]
            Task<HttpResponseMessage> Withdraw([JsonContent] Transaction transaction, CancellationToken cancellationToken = default);
}

var account = await bankClient.GetUser("17", cancellationToken);

我们可以用 Refit，RestEase 或者是 WebApiClientCore 来达到这样的效果， 那么在Dapr 里面使用这些库如何做到呢， 在Dapr的客户端库里面有一个Handler 的官方实现：InvocationHandler。 搭配这个InvocationHandler 就可以和这几个库，在本文中，我们重点介绍Dapr Client 如何搭配 WebApiClientCore。

public interface IBank
{
          [HttpGet(“/accounts/{accountId}”)]
          Task<Account> GetUser(string accountId, CancellationToken cancellationToken = default);

          [HttpPost(“/deposit”)]
          Task<Account> Deposit([JsonContent] Transaction transaction, CancellationToken cancellationToken = default);

          [HttpPost(“/withdraw”)]
          [RawReturn(Enable =true, EnsureSuccessStatusCode = false)]
          Task<HttpResponseMessage> Withdraw([JsonContent] Transaction transaction, CancellationToken cancellationToken = default);
}

  public class WebapiClientExample : Example
   {
       public override string DisplayName => “WebapiClient”;

      private IBank bankClient;

      public WebapiClientExample(IBank bank)
       {
           bankClient = bank;
       }

      public override async Task RunAsync(CancellationToken cancellationToken)
       {
           var options = new JsonSerializerOptions(JsonSerializerDefaults.Web);

           // Scenario 1: Check if the account already exists.
           Account? account = null;
           try
           {
               account = await bankClient.GetUser(“17”, cancellationToken);
           }
           catch (ApiException ex)
           {
               // Account does not exist.
           }

          Console.WriteLine($”Scenario 1: account ’17’ {(account is null ? “does not exist” : “already exists”)}”);

          // Scenario 2: Deposit some money
           var transaction = new Transaction()
           {
               Amount = 100m,
               Id = “17”,
           };

          // read updated balance
           account = await bankClient.Deposit(transaction, cancellationToken);
           Console.WriteLine($”Scenario 2: account ’17’ has ‘{account?.Balance}’ money”);

          // Scenario 3: Handle a validation error without exceptions
           transaction = new Transaction()
           {
               Amount = 1_000_000m,
               Id = “17”,
           };
           HttpResponseMessage response = null;

          response = await bankClient.Withdraw(transaction, cancellationToken);
           if (response.StatusCode != HttpStatusCode.BadRequest)
           {
               // We don’t actually expect this example to succeed – we expect a 400
               Console.WriteLine(“Something went wrong :(“);
               return;
           }
           var problem = await response.Content.ReadFromJsonAsync<ProblemDetails>(cancellationToken: cancellationToken);
           Console.WriteLine($”Scenario 3: got the following errors:”);
           foreach (var kvp in problem!.Errors)
           {
               Console.WriteLine($”{kvp.Key}: {string.Join(“, “, kvp.Value)}”);
           }
       }
   }

var services = new ServiceCollection();
             services.AddTransient<Example, WebapiClientExample>();
             services.AddLogging();

            services
                 .AddScoped<InvocationHandler>()
                 .AddHttpApi<WebapiClientExample.IBank>(o => o.HttpHost = new Uri(“http://bank”))
                 .AddHttpMessageHandler<InvocationHandler>();
            var serviceprovider = services.BuildServiceProvider();

代码的核心部分就在于上面红色的部分，我们把InvocationHandler 加入到AddHttpApi ，就可以和 dapr 一起玩耍了。