ReSharper does lightweight static analysis - I would venture to go as far as to place it into the "code smell analysis" category. Using something like Code Contracts, properly, drastically changes your outlook on static analysis.

ReSharper: you've enumerated this enumerable multiple times. This if statement is redundant. Basically stuff within the scope of a single method.

Code Contracts: you've passed an integer to this function. The function asks that you check that the integer falls into the length of the array that you are also passing in and that it's a multiple of two. Also, the function doesn't promise that it won't return a null value and you are using the result without checking it first. Basically looks at your entire project and can work out code paths across methods.

There's worlds of a difference. ReSharper is definitely useful, but doesn't come close to what proper static analysis can do. If you like what ReSharper is doing for your codebase I thoroughly recommend having a look at Code Contracts (it's a free Microsoft Research project).