HttpContext.Response.WriteAsync("<h1> 你好世界</h1> ") onGet 处理程序方法在 asp.net 核心 6 webapp 中抛出异常

Question

HttpContext.Response.WriteAsync(<h1>hello world</h1>") onGet handler method throws Exception in asp.net core 6 webapp

1. Create asp.net core web app in asp.net 6
2. Update the "OnGet" handler method of Index.cshtml.cs file with below code

     HttpContext.Response.WriteAsync("<h1>hello world</h1>")

3. Run the application and observe the console window for error.

Code Details
-------------
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;

namespace ResponserWrite.Pages
{
    public class IndexModel : PageModel
    {
        private readonly ILogger<IndexModel> _logger;

        public IndexModel(ILogger<IndexModel> logger)
        {
            _logger = logger;
        }

        public void OnGet()
        {
            HttpContext.Response.WriteAsync("<h1>hello world</h1>");
        }
    }
}

Error Details:

fail: Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware[1] An unhandled exception has occurred while executing the request. System.InvalidOperationException: Headers are read-only, response has already started.

Answer 1

It seems that you have a misconception how Razor pages app works. The actual response is generated by the framework using your model ( Something.cshtml.cs ) and the "view"/"page" ( Something.cshtml ). In the model in corresponding methods you need to load/manage the required data and in the page file you change it's representation via modifying output html.

In case if you try to write the response manually it will cause the aforementioned exception when the framework will try to start the response too.

If you want to add some html to index page - just open Index.cshtml and add it somewhere.

Read more:

• Official docs
• Learn Razor Pages