If this code contract sounds like it is validating some or the other collection, then you would be correct. The code contract ForAll will perform validation of IEnumerable collections. This is very handy, because as a developer, you do not need to do any kind of iteration over the collection and writing validation logic. This contract does it for you.
We will create a simple list of integers and populate the list with values. Our code contract will validate that the list does not contain any zero values.
- Before you go on, ensure that you have added the code contracts
usingstatement to the top of yourRecipes.csclass file:using System.Diagnostics.Contracts;
- Add a method called
ValidateList()to your class and pass aList<int>collection to it:public static void ValidateList(List<int> lstValues) { } - Inside the
ValidateList()method, add theContract.ForAllcontract. Interestingly, you will notice that we are usingContract.Asserthere to check whether this list passes our contract conditions. TheContract.ForAllwill use a lambda expression to check that none of the values contained in our list of integers equals zero:public static void ValidateList(List<int> lstValues) { Contract.Assert(Contract.ForAll(lstValues, n => n != 0), "Zero values are not allowed"); } - In the console application, add the relevant
usingstatement to theProgram.csclass to bring the static class into scope:using static Chapter8.Recipes;
- You can then add a simple list of integers containing at least one zero value and pass it to the
ValidateList()method:try { List<int> intList = new List<int>(); int[] arr; intList.AddRange(arr = new int[] { 1, 3, 2, 6, 0, 5}); ValidateList(intList); } catch (Exception ex) { WriteLine(ex.Message); ReadLine(); } - Run the console application and inspect the results in the output:
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