Optional Parameters in C# 4.0

One of the amazing features from C# 4.0 is “Optional Parameters”. It was a feature of VB.Net but it’s now available in C# too. 

I’m not so much involved in this, but I do think there will be some situations where this will be useful to make code more concise.

Consider a standard situation with method overloading or constructor chaining.  In C# we’d have several methods with different signatures where, in effect, we’re indeed just after default values. 

Let’s take the consequence where we’ve got a little helper class to send emails in our application. In some cases we want to CC the administrator to troubleshoot issues; in some cases we want rich HTML emails rather than plain text. We might set up our methods like this:

public void SendMail(string ToAddress, string Body)

{

        this.SendMail(ToAddress, Body, true);

}

public void SendMail(string ToAddress, string Body, bool CcAdministrator)

{

        this.SendMail(ToAddress, Body, CcAdministrator, false);

}

public void SendMail(string ToAddress, string Body, bool CcAdministrator, bool IsBodyHtml)

{

        // the whole Implementation goes here

}

This is a typical method overloading concept and basically we will set default values (true for CC the Admin, and false for HTML emails). 

With new C# 4.0 we can now make the code more short by only having to implement 1 method:

public void SendMail(string ToAddress, string Body, bool CcAdministrator = true, bool IsBodyHtml = false)

{

        // the whole Implementation goes here

}

Now the Magic Begins!

If I call the method by passing a least parameters like this

SendMail("shreekumar@donreturns.com", "This time my return is huge!");

The IL (Intermediate Language) that the C# compiler will generate will actually be the equivalent of this: [See the default values for CcAdministrator and IsBodyHtml]

SendMail("shreekumar@donreturns.com", "This time my return is huge!", true, false);

Another good thing is, here we’ve the ability to skip any parameter (say by skipping a 3^rd parameter CcAdministrator and pass 4^th parameter IsBodyHtml in a function call) like this

SendMail("shreekumar@donreturns.com", "This time my return is huge!", IsBodyHtml:true);

This will allow the code to only pass 3 arguments for conciseness but still invoke the appropriate overload since the IL generated in that instance will be equivalent to this:

SendMail("shreekumar@donreturns.com", "This time my return is huge!", true, true);

Finally, I can say that “Overall It’s a great feature in C# library if used in the correct situations, it can improve our code efficiency greatly”