One way to handle this scenario would be to use reflection and Reflect on expr.Compile().Target.Globals[0].Value which happens to contain information on the given expression including the argument name, value and type however this does seem to defeat the whole purpose.

Example test code that produces the above results:

[Test]
public void ShouldThrowArgumentNullExceptionWhenGivenStringWithNullValue()
{
const string rootDirectory = null;
const string serverName = null;
var server = new WebServer();

TestUtilities.Assert.ThrowsExactly(
() => server.BootstrapServer(0, rootDirectory, serverName));
}

This is sort of doing something similar to what you said though. You’re not actually passing in a lambda (although it does indeed look like one)… in reality you’re passing an Expression (just a piece of code) that gets analyzed and validated inside the validator.

Here’s the post explaining how it works: http://abdullin.com/journal/2008/12/19/how-to-get-parameter-name-and-argument-value-from-c-lambda-v.html

Cheers,

xan

Also, while there is something to be said for the simplicity of your Validator class, it doesn’t solve the issue I’m after. Your “throw new ArgumentNullException(item);” gives no context as to which argument was null. In fact, the thing you’re passing into that constructor, is null itself (which will be less than helpful when debugging/testing). My solution provides you with the parameter name (which is what that constructor argument is supposed to be anyways, not the actual value, which in this case is always null, by definition).

Thanks for the feedback!