[c#] How to use Console.WriteLine in ASP.NET (C#) during debug?

I want to write some result to the console in ASP.NET (C#). It works in a Window application, but a Web application does not work. Here is what I have tried:

protected void btonClick_Click(object sender, EventArgs e)
{
    Console.WriteLine("You click me ...................");
    System.Diagnostics.Debug.WriteLine("You click me ..................");
    System.Diagnostics.Trace.WriteLine("You click me ..................");
}

But I see nothing in the Output panel. How do I solve this problem?

Make sure you start your application in Debug mode (F5), not without debugging (Ctrl+F5) and then select "Show output from: Debug" in the Output panel in Visual Studio.

Trace.Write("Error Message") and Trace.Warn("Error Message") are the methods to use in web, need to decorate the page header trace=true and in config file to hide the error message text to go to end-user and so as to stay in iis itself for programmer debug.

Use response.write method in the code-behind.

If for whatever reason you'd like to catch the output of Console.WriteLine, you CAN do this:

protected void Application_Start(object sender, EventArgs e)
{
    var writer = new LogWriter();
    Console.SetOut(writer);
}

public class LogWriter : TextWriter
{
    public override void WriteLine(string value)
    {
        //do whatever with value
    }

    public override Encoding Encoding
    {
        get { return Encoding.Default; }
    }
}

You shouldn't launch as an IIS server. check your launch setting, make sure it switched to your project name( change this name in your launchSettings.json file ), not the IIS.

using System.Diagnostics;

The following will print to your output as long as the dropdown is set to 'Debug' as shown below.

Debug.WriteLine("Hello, world!");