How to show Console.WriteLine output in my browser console or output window?

Solution 1:

Console.WriteLine(...) will not be displayed. If you absolutely need to see output in the debugger, you'll have to use

System.Diagnostics.Debug.WriteLine("This will be displayed in output window");

and view it in the Output window. You can open the output window by going to Debug -> Window -> Output:

Here's an example of what this will all look like:

For further readings, check out this SO post.

Solution 2:

You can write to your Javascript console from your C# Code using the following class

using System.Web;

public static class Javascript
{
    static string scriptTag = "<script type=\"\" language=\"\">{0}</script>";
    public static void ConsoleLog(string message)
    {       
        string function = "console.log('{0}');";
        string log = string.Format(GenerateCodeFromFunction(function), message);
        HttpContext.Current.Response.Write(log);
    }

    public static void Alert(string message)
    {
        string function = "alert('{0}');";
        string log = string.Format(GenerateCodeFromFunction(function), message);
        HttpContext.Current.Response.Write(log);
    }

    static string GenerateCodeFromFunction(string function)
    {
        return string.Format(scriptTag, function);
    }
}

Works just like its JS version, it actually converts your message to JS and injects it into the page.

Solution 3:

You can use Debug.Writeline("debug information"). It will be displayed in the Output window.

Solution 4:

In addition to Sam's answer, you may find Response.Write useful. In some situations - for example, when you are supporting legacy inline .aspx pages - it's more convenient to debug by writing out suspect values to the browser:

String myString = GetAStringFromSomewhere();

/* What did that method actually return, anyway?
   NB: Remove this once I know! */
Response.Write(myString);

This is less practical in ASP.Net MVC, however, as your controllers will be compiled. In this case, you might as well be writing out your debugging information to a log file, using something like log4net.

Solution 5:

Thanks +MichaelTaylor3D for the solution, I have further enhanced it a little bit to support the function during ajax partial postback. Remember to add reference to System.Web.Extension to support ScriptManager.

    public static class Javascript
    {
        static string scriptTag = "<script type=\"\" language=\"\">{0}</script>";
        public static void ConsoleLog(string message)
        {
            string function = "console.log('{0}');";
            string log = string.Format(GenerateCodeFromFunction(function), message);

            Page page = HttpContext.Current.Handler as Page;

            if (ScriptManager.GetCurrent(page).IsInAsyncPostBack)
            {
                ScriptManager.RegisterClientScriptBlock(page, page.GetType(), "log", "console.log('" + message + "')", true);
            }
            else
            {
                HttpContext.Current.Response.Write(log);
            }
        }

        public static void ConsoleError(string message)
        {
            string function = "console.error('{0}');";
            string log = string.Format(GenerateCodeFromFunction(function), message);

            Page page = HttpContext.Current.Handler as Page;

            if (ScriptManager.GetCurrent(page).IsInAsyncPostBack)
            {
                ScriptManager.RegisterClientScriptBlock(page, page.GetType(), "error", "console.error('" + message + "')", true);
            }
            else
            {
                HttpContext.Current.Response.Write(log);
            }
        }

        public static void Alert(string message)
        {
            string function = "alert('{0}');";
            string log = string.Format(GenerateCodeFromFunction(function), message);

            Page page = HttpContext.Current.Handler as Page;

            if (ScriptManager.GetCurrent(page).IsInAsyncPostBack)
            {
                ScriptManager.RegisterClientScriptBlock(page, page.GetType(), "alert", "alert('" + message + "')", true);
            }
            else
            {
                HttpContext.Current.Response.Write(log);
            }
        }

        static string GenerateCodeFromFunction(string function)
        {
            return string.Format(scriptTag, function);
        }
    }