IHttpContextAccessor.HttpContext 为 null WebForms

问：

当我将 API 从 .NET Framework 4.8 调用到 .NET Core 时，我一直在尝试使用 IHttpContextAccessor.HttpContext 读取当前的 HttpContext。

我已将其添加到服务中：

services.AddHttpContextAccessor()
services.AddTransient<IService, Service>();

我在类中获得了 HttpContextAccessor，但 HttpContext 始终为 null：

页：

Private ReadOnly service As IService
Private httpContextAccessor As Microsoft.AspNetCore.Http.IHttpContextAccessor
Public Sub New(ByVal service As IService, ..., httpContextAccessor As IHttpContextAccessor)
    Me.service = service
    ...
    Me.httpContextAccessor = httpContextAccessor'<-- in debug mode I can see that HttpContext is null here also
End Sub

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

End Sub

Public Async Sub button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles button1.Click
        Dim httpContext = httpContextAccessor.HttpContext              '<--this is null
        Dim results = await service.Method()
    End Sub

服务业：

private readonly IHttpContextAccessor httpContextAccessor;

public Service(..., IHttpContextAccessor httpContextAccessor,...)
{
    this.httpContextAccessor = httpContextAccessor; //<-- in debug mode I can see that HttpContext is null here also
}

public async Task<List<ModelDTO>> Method()
{
    var httpContext = httpContextAccessor.HttpContext; //<-- Also null here.
    ...
}

如果它在那里不为空，我会将其从页面传递到服务。我已经读过一些关于它的东西，但无法弄清楚这一点。

例如

在这里 - 我尝试更改按钮，使其不是异步的，并且希望在进入方法之前填充 httpContext，但事实并非如此。

我还看到了一些关于如何实现 IHttpContextAccessor 的建议，我认为我通过复制它正确地完成了它。