Writing to output window of Visual Studio

This will write to the debug output window:

using System.Diagnostics;

Debug.WriteLine("Send to debug output.");

Add the System.Diagnostics namespace, and then you can use Debug.WriteLine() to quickly print a message to the output window of the IDE. For more details, please refer to these:

• How to trace and debug in Visual C#
• A Treatise on Using Debug and Trace classes, including Exception Handling

Debug.WriteLine

is what you're looking for.

If not, try doing this:

Menu Tools → Options → Debugging → uncheck Send Output to Immediate.