expression involves a data type that is new since the last build
You added or changed an expression to involve a data type that is new to your source code since the last successful build. Edit and Continue only supports data types that were present in your source code during the latest build.
To remove this warning without ending the current debug session, change the expression back to its state before it produced this warning. Then select the Apply Code Changes command on the Debug menu.
To remove this warning without changing your source code, stop the current debug session by selecting Stop Debugging from the Debug menu. Select Build from the Build menu. After a successful build, you may debug the current source code.
This warning will always be followed by a C1092 error. For further information, see the Limitations of Edit and Continue.