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

Question

I wrote System.Console.WriteLine("How can I see this debugging information in a browser"); in the model of my ASP.NET MVC4 project. How can I see this debugging string in the browser console, or at least in Visual Studio?. I can't find it in the output window of Visual Studio. Maybe I need to install some plugin from NuGet?

@adt No. `Console.WriteLine` will not display in the output window because it is invoked by the Browser in ASP. — StoriKnow, Feb 05 '13 at 18:15

score 48 · Accepted Answer · edited May 23 '17 at 12:34

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:

enter image description here

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

enter image description here

For further readings, check out this SO post.

MichaelTaylor3D · Answer 2 · 2016-03-21T18:02:08.223

24

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.

edited Mar 21 '16 at 18:02

answered Jun 09 '14 at 20:01

MichaelTaylor3D

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tested it on MVC5 and it doesnt work... should do an extra config? – Nacho Jan 29 '15 at 12:05
1

what doesnt work? I can try to help if I have more information. – MichaelTaylor3D Jan 29 '15 at 12:13
1

HttpContext is not defined in this snippet – brennanyoung Mar 21 '16 at 14:15
1

True, you need to make sure that the System.Web namespace is defined. Ill add that to my answer. – MichaelTaylor3D Mar 21 '16 at 17:59
I kept getting a "Newline in Constant" error, until I changed the scriptTag declaration to `static string scriptTag = " – Joe Coyle Feb 28 '19 at 13:57

score 6 · Answer 3 · edited Jun 16 '17 at 09:12

6

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

edited Jun 16 '17 at 09:12

Liam

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answered Feb 05 '13 at 17:57

user1797792

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1

@Burgi It was also written and posted *before* the accepted answer was. – TylerH May 23 '19 at 14:30

Ant P · Answer 4 · 2013-02-05T18:58:06.113

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.

score 1 · Answer 5 · answered Nov 19 '15 at 07:54

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);
        }
    }

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

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