Throwing ArgumentNullException

Question

Suppose I have a method that takes an object of some kind as an argument. Now say that if this method is passed a null argument, it\'s a fatal error and an exception shoul

Answer 1

You can use syntax like the following to not just throw an ArgumentNullException but have that exception name the parameter as part of its error text as well. E.g.;

void SomeMethod(SomeObject someObject)
{
    Throw.IfArgNull(() => someObject);
    //... do more stuff
}

The class used to raise the exception is;

public static class Throw
{
    public static void IfArgNull(Expression> arg)
    {
        if (arg == null)
        {
            throw new ArgumentNullException(nameof(arg), "There is no expression with which to test the object's value.");
        }

        // get the variable name of the argument
        MemberExpression metaData = arg.Body as MemberExpression;
        if (metaData == null)
        {
            throw new ArgumentException("Unable to retrieve the name of the object being tested.", nameof(arg));
        }

        // can the data type be null at all
        string argName = metaData.Member.Name;
        Type type = typeof(T);
        if (type.IsValueType && Nullable.GetUnderlyingType(type) == null)
        {
            throw new ArgumentException("The expression does not specify a nullible type.", argName);
        }

        // get the value and check for null
        if (arg.Compile()() == null)
        {
            throw new ArgumentNullException(argName);
        }
    }
}