C# Edit and Continue: error 4009

Updating a [using alias | field | event | fixed size buffer | constant | attribute] will prevent the debug session from continuing while Edit and Continue is enabled

This error indicates that you tried to modify a using alias, field initializer, attribute target, or attribute arguments.

Consider the following example code:

class Program


   private int Example = 10;

   static void Main() { }


If you step into the application, then try to change the Example = 10 to Example = 20, the error occurs.

To correct this error

  • Undo the changes, then continue debugging without the changes


    On the Debug menu, click Stop Debugging, make the changes, then start a new debugging session.

See Also


event (C# Reference)

using (C# Reference)

Supported Code Changes (C#)

Edit and Continue (Visual C#)

Other Resources

Edit and Continue Errors and Warnings (C#)