What is the proper way to check for null values?

Question

I love the null-coalescing operator because it makes it easy to assign a default value for nullable types.

 int y = x ?? -1;

That\'s great,

Answer 1

My preference, for a one off, would be to use a safe cast to string in case the object stored with the key isn't one. Using ToString() may not have the results you want.

var y = Session["key"] as string ?? "none";

As @Jon Skeet says, if you find yourself doing this a lot an extension method or, better, yet maybe an extension method in conjunction with a strongly typed SessionWrapper class. Even without the extension method, the strongly typed wrapper might be a good idea.

public class SessionWrapper
{
    private HttpSessionBase Session { get; set; }

    public SessionWrapper( HttpSessionBase session )
    {
        Session = session;
    }

    public SessionWrapper() : this( HttpContext.Current.Session ) { }

    public string Key
    {
         get { return Session["key"] as string ?? "none";
    }

    public int MaxAllowed
    {
         get { return Session["maxAllowed"] as int? ?? 10 }
    }
}

Used as

 var session = new SessionWrapper(Session);

 string key = session.Key;
 int maxAllowed = session.maxAllowed;