What is the smoothest, most appealing syntax you've found for asserting parameter correctness in c#?

Question

A common problem in any language is to assert that parameters sent in to a method meet your requirements, and if they don\'t, to send nice, informative error messages. This

Answer 1

Wow, I found something really interesting here. Chris above gave a link to another Stack Overflow question. One of the answers there pointed to a blog post which describes how to get code like this:

public static void Copy(T[] dst, long dstOffset, T[] src, long srcOffset, long length)
{
    Validate.Begin()
            .IsNotNull(dst, “dst”)
            .IsNotNull(src, “src”)
            .Check()
            .IsPositive(length)
            .IsIndexInRange(dst, dstOffset, “dstOffset”)
            .IsIndexInRange(dst, dstOffset + length, “dstOffset + length”)
            .IsIndexInRange(src, srcOffset, “srcOffset”)
            .IsIndexInRange(src, srcOffset + length, “srcOffset + length”)
            .Check();

    for (int di = dstOffset; di < dstOffset + length; ++di)
        dst[di] = src[di - dstOffset + srcOffset];
}

I'm not convinced it is the best answer yet, but it certainly is interesting. Here's the blog post, from Rick Brewster.