Checking arguments of a method

If you are not using the Argument class, you are definitely missing something! It allows you to check for a method input and make sure it is valid. So, instead of writing this:

public void DoSomething(string myInput)
{
    if (string.IsNullOrWhitespace(myInput)
    {
        Log.Error("Argument 'myInput' cannot be null or whitespace");
        throw new ArgumentException("Argument 'myInput' cannot be null or whitespace", "myInput");
    }

    // custom logic
}

You can write this:

public void DoSomething(string myInput)
{
    Argument.IsNotNullOrWhitespace(() => myInput);

    // custom logic
}

However, when you are writing lots of code, then even this piece of code can be too much. Thanks to the Catel.Resharper plugin, it is possible to select the argument (in this case myInput), hit ALT + Enter and generate the code, just like the video below:

Below is a table what argument checks are available per type:

.NET Type	Available checks	Exception type	Constraint text
Any reference type	IsNotNull	ArgumentNullException	The <paramref name="[paramname]"/> is <c>null</c>
	ImplementsInterface	ArgumentException	The <paramref name="[paramname]"/> does not implement the <see cref=”[interface]” /> interface
	IsOfType	ArgumentException	The <paramref name="[paramname]"/> is not of type <see cref=”[type]” />
Array	IsNotNullOrEmptyArray	ArgumentException	The <paramref name="[paramname]"/> is <c>null</c> or an empty array
Int / decimal / double / float	IsNotOutOfRange	ArgumentOutOfRangeException	The <paramref name="[paramname]"/> is not between <c>[min]</c> and <c>[max]</c>
	IsMinimal	ArgumentOutOfRangeException	The <paramref name="[paramname]"/> is smaller than <c>[value]</c>
	IsMaximal	ArgumentOutOfRangeException	The <paramref name="[paramname]"/> is larger than <c>[value]</c>
String	IsNotNullOrEmpty	ArgumentException	The <paramref name="[paramname]"/> is <c>null</c> or empty
	IsNotNullOrWhitespace	ArgumentException	The <paramref name="[paramname]"/> is <c>null</c> or whitespace
	IsMatch	ArgumentException	The <paramref name="[paramname]"/> doesn’t match with pattern <c><![CDATA[[pattern]]]></c>.
	IsNotMatch	ArgumentException	The <paramref name="[paramname]"/> does match with pattern <c><![CDATA[[pattern]]]></c>.
Guid	IsNotNullOrEmpty	ArgumentException	The <paramref name="[paramname]"/> is <c>null</c> or empty
Type	ImplementsInterface	ArgumentException	The <paramref name="[paramname]"/> does not implement the <see cref=”[interface]” /> interface
Type	IsOfType	ArgumentException	The <paramref name="[paramname]"/> is not of type <see cref=”[type]” />