響應內容長度不匹配：寫入的字節太少

Question

我的 ASP.NET 核心應用程序使用“開箱即用”外部登錄身份驗證。 What I want to implement - on facebook challenge I want to wrap redirect url and return it as json to consume in jquery frontend. 但是在請求結束后，我在瀏覽器中看到 500 錯誤，在應用程序控制台中看到下一個錯誤：

失敗：Microsoft.AspNetCore.Server.Kestrel[13] 連接 ID“0HLV651D6KVJC”，請求 ID“0HLV651D6KVJC:00000005”：應用程序引發了未處理的異常。 System.InvalidOperationException：響應內容長度不匹配：寫入的字節太少（470 個中的 0 個）。

我的外部登錄操作，沒什么特別的

[HttpPost]
[AllowAnonymous]
[ValidateAntiForgeryToken]
public IActionResult ExternalLogin(string provider, string returnUrl = null)
{
    // Request a redirect to the external login provider.
    var redirectUrl = Url.Action(nameof(ExternalLoginCallback), "Account", new { returnUrl });
    var properties = _signInManager.ConfigureExternalAuthenticationProperties(provider, redirectUrl);
    return Challenge(properties, provider);
}

Facebook認證配置：

services.AddAuthentication().AddFacebook(facebookOptions =>
{
    facebookOptions.AppId = Configuration["Authentication:Facebook:AppId"];
    facebookOptions.AppSecret = Configuration["Authentication:Facebook:AppSecret"];

    facebookOptions.Events.OnRedirectToAuthorizationEndpoint =
        async (x) =>
        {

            UTF8Encoding encoding = new UTF8Encoding();
            var content = JsonConvert.SerializeObject(new { redirect_url = x.RedirectUri });
            byte[] bytes = encoding.GetBytes(content);

            x.Response.StatusCode = 200;
            x.Response.ContentLength = bytes.Length;
            x.Response.ContentType = "text/plain";
            x.Response.Body = new MemoryStream();

            await x.Response.WriteAsync(content);
            // at this point I see that x.Response.Body.Length == 470, but message states there are 0 of 470 written
        };
});

有什么辦法可以讓它工作嗎？

Answer 1

當使用新的 C# using如下語法時，也會發生這種情況：

using var ms = new MemoryStream();
using var writer = new StreamWriter(ms);
writer.WriteLine("my content");
memoryStream.Position = 0;
return File(ms, "text/plain");

在這種情況下， MemoryStream在StreamWriter被刷新之前被訪問。 對StreamWriter使用舊語法：

using var ms = new MemoryStream();
using (var writer = new StreamWriter(ms, Encoding.UTF8, -1, true))
{
    writer.WriteLine("my content");
}
memoryStream.Position = 0;
return File(ms, "text/plain");

或刷新作家：

using var ms = new MemoryStream();
using var writer = new StreamWriter(ms);
writer.WriteLine("my content");
writer.Flush();
memoryStream.Position = 0;
return File(ms, "text/plain");

Answer 2

更改代碼以寫入原始響應 stream 並且它現在可以工作。

facebookOptions.Events.OnRedirectToAuthorizationEndpoint =
    async (x) =>
    {
        var content = JsonConvert.SerializeObject(new { redirect_url = x.RedirectUri });

        x.Response.StatusCode = 200;
        x.Response.ContentType = "text/plain";

        await x.Response.WriteAsync(content);
    };

Answer 3

你可以使用這樣的東西：

var stream = new MemoryStream();
/// writing to the stream
if (stream.CanSeek)
{
   stream.Seek(0, SeekOrigin.Begin);
}
/// then read stream