Brian Keating | .NET 4.0 Code Contracts

Yesterday I read an interesting article on a flight home from Amsterdam and though I would share it with you.

One of the generally excepted approaches of writing functions is to validate you input arguments before using them, If-Then-Throw pattern.

Now .Net 4.0 supports Design by Contract approach to software design .NET 4 code contracts. Lets dive straight in (as always Smile )

   1:  using System.Diagnostics.Contracts;

2:

   3:  public class Calculator

   4:  {

   5:      public Int32 Sum(Int32 x, Int32 y)

   6:      {

   7:          Contract.Requires<ArgumentOutOfRangeException>(x >= 0 && y >= 0);

   8:          Contract.Ensures(Contract.Result<Int32>() >= 0);

9:

  10:          if (x == y)

  11:          return 2 * x;

  12:          return x + y;

  13:      }

14:

  15:      public Int32 Divide(Int32 x, Int32 y)

  16:      {

  17:          Contract.Requires<ArgumentOutOfRangeException>(x >= 0 && y >= 0);

  18:          Contract.Requires<ArgumentOutOfRangeException>(y > 0);

  19:          Contract.Ensures(Contract.Result<Int32>() >= 0);

  20:          return x / y;

  21:      }

  22:  }

Here we see just how powerful contracts can be, have a look at Dino Esposito’s article above for more information.

.NET 4.0 Code Contracts