I was looking at the Util class that we use in our website and decided to put the code here on the blog. I'll create a post for each method, but be aware, the code isn't always the most optimized and some of it was written over 6 years ago. 

Let's start with something simple

public static bool LegalEmail(string email) {
    if (email == null) return false;
    if (email.Length < 6) return false;
    if (email.IndexOf("@") == -1) return false;

    return (Regex.Match(email, @"^[a-z0-9\._-]+@[a-z0-9\._-]+\.+[a-z0-9]{2,4}$", RegexOptions.IgnoreCase).Length != 0);
}

This method simply checks if the string is a legal email address. Now that .Net support extension in v3.5 I guess it's time to change this into an extension, so instead of writing

string email = "example@example.com";
if (Util.LegalEmail(email)) {
    //do stuff
}

you can write

string email = "example@example.com";
if (email.LegalEmail()) {
    //do stuff
}