Blazor Error Headers are read-only, response has already started

[KhaledHani02]

Hi I'm trying to implement Log in method with Identity

public async Task<bool> LoginAsync(LogInHMI loginModel)
{
    try
    {
        var user = await _userManager.FindByNameAsync(loginModel.UserName);
        if (user == null)
            return false;

        var result = await _signInManager.PasswordSignInAsync(user.UserName, loginModel.Password, isPersistent: false, lockoutOnFailure: false);
        return result.Succeeded;
    }
    catch (Exception ex)
    {
        throw new Exception(ex.Message);
    }
}

and i'm getting this error:
System.InvalidOperationException: 'Headers are read-only, response has already started.'

[javiercn]

@KhaledHani02 thanks for contacting us.

You likely are using [StreamingRendering] and that is incompatible with Identity as it needs to be able to set headers.

[KhaledHani02]

I'm using :
@rendermode InteractiveServer

[MackinnonBuck]

@guardrex, do you happen to know if this behavior is documented anywhere? We've seen issue reports like this a couple times. Headers can't be set after the response has already started, so if you're doing stream rendering and you attempt to set a header after the first render (e.g., by calling SignInManager.PasswordSignInAsync()), then this causes an error. A similar limitation exists for interactive rendering.

If this isn't documented, we should probably do so. Maybe we add some more details to https://learn.microsoft.com/aspnet/core/blazor/components/httpcontext?view=aspnetcore-10.0

[guardrex]

We do have remarks to that effect, but I'll need to research the context and see what we say and where. I've opened dotnet/AspNetCore.Docs#35544 to work on it.

[KhaledHani02]

Hello guys, I solved the identity issue by scaffolding the login pages, etc. But now there is the problem with @rendermode InteractiveServer which no longer renders the program interactively. I read that this problem is related to Blazor's SignalR.
Do you know anything about it?