Refactoring Guard Clauses

Question

What approaches do people take (if any) in managing guard clause explosion in your classes? For example:

public void SomeMethod<T>(string var1, IEnumerable<T> items, int count)
{
    if (string.IsNullOrEmpty(var1))
    {
        throw new ArgumentNullException("var1");
    }

    if (items == null)
    {
        throw new ArgumentNullException("items");
    }

    if (count < 1)
    {
        throw new ArgumentOutOfRangeException("count");
    }

    ... etc ....
}

In the project that I am currently working on there are many classes that have a similar set of guard clauses on the public methods.

I am aware of the .NET 4.0 Code Contracts however this is not an option for our team at the moment.

Answer 1

A lot of projects that I've seen use a static Guard class.

public static class Guard {
    public static void ArgumentIsNotNull(object value, string argument) {
        if (value == null)
            throw new ArgumentNullException(argument);
    }
}

It makes the code a lot cleaner, in my opinion.

Guard.ArgumentIsNotNull(arg1, "arg1");

Answer 2

If you don't want to go down the Code Contracts route, one way to simplify it is to remove the braces:

public void SomeMethod<T>(string var1, IEnumerable<T> items, int count)
{
    if (string.IsNullOrEmpty(var1))
        throw new ArgumentNullException("var1");

    if (items == null)
        throw new ArgumentNullException("items");

    if (count < 1)
        throw new ArgumentOutOfRangeException("count");

    ... etc ....
}

Other than that, there are some ways that you can simulate Code Contracts, if your objection is that .Net 4.0 is not prime time yet:

http://geekswithblogs.net/Podwysocki/archive/2008/01/22/118770.aspx

Answer 3

You might consider refactoring to Introduce a Null Object.

Answer 4

Meanwhile there's an excellent article about this here: http://haacked.com/archive/2013/01/05/mitigate-the-billion-dollar-mistake-with-aspects.aspx/

I would consider to use NullGuard.Fody as I'm excited about Fodys abilities to reduce boilerplate code