(This is a subset of Pathoschild.DesignByContract that contains the annotations but does not enforce them.) Enables code contracts on methods and properties. By annotating your code with attributes like [NotNull], you can remove common validation code and provide helpful exception messages, making your code more robust and refactor-safe. These annotation attributes are also recognized by ReSharper when it has an equivalent annotation, which gives you real-time feedback on contract violations as you type.