Won't compile - File missing error

[bloukewer]

When trying to compile my project, the following error message appears:

"An unhandled exception of type 'System.IO.FileNotFoundException' occurred in LoneBewerker2004.exe

Additional information: File or assembly name System.Data, or one of its dependencies, was not found."

It highlights the first line of my main-class. "Friend class Main"

I reckon the problem isn't with my code, cause the same project compiled perfectly before. Can anyone help me salvage what's left of my new year?

 

[JuggaloBrotha]

so if i hits a compile error on the declaration of the class try changing it to:
Public Class Main

 

[bloukewer]

Simple

Do know why, but the "Play" button didn't do the trick. All I had to do was to build the project again

 

[JuggaloBrotha]

that tricky play button, come to think of it i did have 1 case where the play (run app) toolbar button caused an error on something but going to the menu and clicking Build App worked just fine