asp.net - Blazor WebAssembly : The provided ContentType is not supported;

Question

我今天通过以下命令行安装了 Blazor WebAssembly 示例项目 (WeatherForecast):

dotnet new blazorwasm --hosted -o ProjectName

我在 Debug模式下通过 Visual Studio 2019 安装后直接启动了 SPA。浏览器是:Chrome。浏览器显示应用程序，但是当我选择导航菜单“获取数据”时，什么也没有发生。 Chrome 显示 1 个错误:

Microsoft.AspNetCore.Components.WebAssembly.Rendering.WebAssemblyRenderer[100]
      Unhandled exception rendering component: The provided ContentType is not supported; the supported types are 'application/json' and the structured syntax suffix 'application/+json'.
System.NotSupportedException: The provided ContentType is not supported; the supported types are 'application/json' and the structured syntax suffix 'application/+json'.
  at System.Net.Http.Json.HttpContentJsonExtensions.ValidateContent (System.Net.Http.HttpContent content) <0x2e87f38 + 0x0009a> in <filename unknown>:0 
  at System.Net.Http.Json.HttpContentJsonExtensions.ReadFromJsonAsync[T] (System.Net.Http.HttpContent content, System.Text.Json.JsonSerializerOptions options, System.Threading.CancellationToken cancellationToken) <0x2e87d30 + 0x00006> in <filename unknown>:0 
  at System.Net.Http.Json.HttpClientJsonExtensions.GetFromJsonAsyncCore[T] (System.Threading.Tasks.Task`1[TResult] taskResponse, System.Text.Json.JsonSerializerOptions options, System.Threading.CancellationToken cancellationToken) <0x2e40838 + 0x0011c> in <filename unknown>:0 
  at BlazorIssue.Client.Pages.FetchData.OnInitializedAsync () [0x00033] in D:\Projects\BlazorIssue\Client\Pages\FetchData.razor:43 
  at Microsoft.AspNetCore.Components.ComponentBase.RunInitAndSetParametersAsync () <0x2b8cb98 + 0x0013a> in <filename unknown>:0 
  at Microsoft.AspNetCore.Components.RenderTree.Renderer.GetErrorHandledTask (System.Threading.Tasks.Task taskToHandle) <0x2dd8340 + 0x000b6> in <filename unknown>:0 

Chrome 显示以下请求 header :

上下文信息:

Chrome :V83.0.4103.61(64位)

Blazor:V3.2.0

Visual Studio:V16.6.0

点网 V3.1.300

DotNet SDK:V3.1.300

这很奇怪，因为这个示例项目的全新安装昨天没有问题。

Answer 1

如果客户端项目被指定为启动项目，这可能发生在 Web 程序集模板项目的 ASP.NET 托管版本中。确保将服务器项目设置为启动项目。