With C# 4.0 (2010), the support for this feature has been added to the language. The new Optional Arguments in C# 4.0 allows you to specify the default values of parameters in case there values are not provided from the function call. Here's a small example to illustrate the basics of Optional Arguments in C#:
//C#
// Function with optional arguments
void OptionalArgExample(int reqdField, string opt = "default value")
{
// do something
}
// Calling the method with just the required argument
OptionalArgExample(10);
// Calling the method with both the arguments
OptionalArgExample(10, "some text");
For more information, read the MSDN article on Named and Optional Arguments in C#