Question

I am creating a file in C# (.NET Web Service) and do not want to overwrite an existing file.

The way seems to be to construct a FileStream with FileMode.CreateNew set. It does in fact throw an exception if the file exists.

But how do I recognize this exception as opposed to other possible exceptions thrown by the file creation? The documentation at http://msdn.microsoft.com/en-us/library/47ek66wy.aspx lists this case as an “IOException” which clearly is vague as other things can cause this.

Is the answer here that I catch IOException and then just do a File.Exists?

Answer 1

You can get error code from the exception as the following:

int hr = Marshal.GetHRForException( ex );

For file exists it will be 0x80070050.