.net - 服务器端 Blazor 不提供 HttpClient 进行注入

Question

当我尝试注入 HttpClient 时，剃刀页面出现错误：

未处理的承诺拒绝：错误：System.InvalidOperationException：无法为 type 上的属性“Http”提供值。没有“System.Net.Http.HttpClient”类型的注册服务。

请审查并提供反馈。

Answer 1

如果您提供代码片段您正在尝试做的事情，那么回答您的问题会更容易。但是没问题。现在我将向您展示一个示例，使用 DI 注入服务。

ChartDataService.cs


namespace MyBlazorApp.Services 
{

  public class ChartDataService: IChartDataService
  {
    public HttpClient httpClient;
    
    public ChartDataService(HttpClient httpClient) 
    {
      this.httpClient = httpClient;
    }

    public async Task < IEnumerable < ChartData >> GetChartData()
    {
      return await httpClient.GetJsonAsync < ChartData[] > ($ "myUri");
    }
  }
}

IChartDataService.cs

namespace MyBlazorApp.Services 
{
  public interface IChartDataService 
  {
    Task < IEnumerable < ChartData >> GetChartData();
  }
}

Startup.cs
// other

public void ConfigureServices(IServiceCollection services) 
{
    services.AddRazorPages();
    services.AddServerSideBlazor();
    // some services
    services.AddHttpClient < IChartDataService, ChartDataService > (client => 
    {
      client.BaseAddress = new Uri(myBaseUri);
    });    
}

MyRazorPage.razor.cs (when using code Behind)

[Inject] private IChartDataService ChartDataService { get; set; }

or in
MyRazorPage.razor

@code
{
[Inject] private IChartDataService ChartDataService { get; set; }
}

then in your code - block or code - behind file u can use something like this,
  for example, in an async function..

protected override async Task OnInitializedAsync() 
{
  chartData = await ChartDataService.MakeChartData();
}

Answer 2

在Razor Component它不需要@inject

请参见下面的示例：

<div class="row">
    <div class="col-4">
        <label for="cities">Choose city</label>
        <input type="text" class="form-control" id="citiy" @bind="@cityName" />         
    </div>
    <div class="col-3">
        <button class="btn btn-primary" @onclick=@GetWeather>Get weather for @cityName</button>
    </div>
</div>
<div class="row">
    <div class="col-8 offset-2">
        <pre id="json"><code>@ResultStr</code></pre>
   </div>
</div>

而这@code部分

@code {

    string cityName = "";
    string ResultStr= "...";
    string reqUrl => $"http://api.openweathermap.org/data/2.5/weather?q={cityName}&APPID=appID";

    async Task GetWeather()
    {
        try
        {
            HttpClient client = new HttpClient();
            ResultStr= "...";
            var response = await client.GetAsync(reqUrl);
            if (response.IsSuccessStatusCode)
                ResultStr= await response.Content.ReadAsStringAsync();
            else
                ResultStr= response.ReasonPhrase;
        }
        catch (Exception ex)
        {
             ResultStr= ex.ToString();
        }
    }
}

这对我有用.. =)

Answer 3

该消息说您需要在文件 Program.cs 中注册服务 HTTP

如果你使用 Net6，你可以用这一行注册：

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddHttpClient();