It would be great if R# could generate checks on parameters passed into public functions. For instance, looking at the screen-shot there are 3 numbered items.
One could right click at point 1 and have R# generate the following for the 'input1' parameter:
if( input1 == null || input1.Length == 0 )
throw new ArgumentNullException( @"input1",
@"The parameters passed was null or empty." );
... and similar for input2:
if( input2== null )
throw new ArgumentNullException( @"input2,
@"The parameters passed was null." );
..and for the return value:
if( s== null || s.Length == 0 )
throw new ArgumentNullException( @"s",
@"The parameter being returned is null which breaks the contract." );
or something similar, if indeed it does break the contract.