Question

I have the following in an interface:

string GetTopic(string rk);

and this function:

public string GetTopic(string rk)
{
    return string.Format("{0}.{1}.{2}",
        rk.Substring(0, 2).TrimStart('0'),
        rk.Substring(2, 2).TrimStart('0').PadLeft(1, '0'),
        rk.Substring(4, 2).TrimStart('0').PadLeft(1, '0'));
}

I would like to add an optional second parameter, enabling the function to be called like this:

var a = GetTopic("010101") 

or

var b = GetTopic("010101","test")

In the first case I would like to get the output “1.1.1” and in the second case the output “1.1.1 – test”.

Is this possible or do I need to make two functions and have one overload the other one? How can I specify the optional second parameter in my interface?

Answer 1

You can set a default:

public string GetTopic(string rk, string anotherParam = "")
{
    String append = (String.IsNullOrEmpty(anotherParam)) ? "" : " - " + anotherParam;
    return string.Format("{0}.{1}.{2}{3}",
        rk.Substring(0, 2).TrimStart('0'),
        rk.Substring(2, 2).TrimStart('0').PadLeft(1, '0'),
        rk.Substring(4, 2).TrimStart('0').PadLeft(1, '0'),
        append);
}

so “anotherParam” will be test if you call:

var a = GetTopic("010101");

And for your interace-definition:

public interface IUtilityService 
{ 
    string GetTopic(string rk, string suffix = ""); 
} 

MSDN: http://msdn.microsoft.com/de-de/library/dd264739.aspx