Information about the .ascx (ascx) file type

Below is all the information we have available on file about the .ascx (ascx) file type.

.ascx
Visual Studio/ASP.NET Custom User Control source file.

Where this is available we would like to include file format information on .ascx files, as well as information on how to view or open files of type .ascx. If you know of any information which we have missed then please let us know.