Creating code contract ValueAtReturn method

The best example we can think of when using the code contract ValueAtReturn is out parameters. Personally, I do not use out parameters often, but there are times when you need to use them. Code contracts make provision for this, and you can check the value at the time it is returned.

Getting ready

We will create a simple method that subtracts a value from a parameter. The out parameter will be validated by the code contract, and the result will be output to the console window.

How to do it…

1. Before you go on, ensure that you have added the code contracts using statement to the top of your Recipes.cs class file:

   using System.Diagnostics.Contracts;

2. In the Recipes class, create a new method called ValidOutValue() and pass an out parameter called secureValue to it:

   public static void ValidOutValue(out int secureValue)
   {
       
   }

3. Finally, add Contract.ValueAtReturn to the method. Interestingly, you will note that this needs to be contained in Contract.Ensures...