Check if a file is modified in a custom build event in VS2008

I'm using a cust开发者_如何学Goom build step to generate gSoap code from a .wsdl file during my build. Is there any way to get Visual Studio to skip this step if the .wsdl file has not been modified since the Soap stubs were created?

I'm referring to VS2005 but i think this is the same for VS2008

When defining your custom build step, you need to enter your source files into "Additional Dependencies" and the generated files into "Output". This helps VS to decide whether the output needs to be rebuild. This is always done if the timstamp of any of the input files is newer than the output.

If no dependencies or outputs are defined there is no way for VS to tell if the build is up to date, hence VS will always run this build step.