C# Optional Parameters

Optional parameters were introduced with .NET 4.0. You just only give default value these parameters.

1. public void DoSomething(int x, string s = "test")
2. {
3.    //Do something
4. }

1. //Calling methods
2. DoSomething(1);
3. DoSomething(2, "abc");

There are other some ways to use optional parameters.
Method overloading

1. public void DoSomething(int x, string s)
2. {
3.    //Do something
4. }
5.                
6. public void DoSomething(int x)
7. {
8.    DoSomething(x, "test");
9. }

params keyword

1. public void DoSomething(params object[] obj)
2. {
3.    //Do something
4. }

Optional attribute

1. using System.Runtime.InteropServices;
2.  
3. public void DoSomething(int x, [Optional, DefaultParameterValue("test")] string s)
4. {
5.    //Do something
6. }

Nullable types

1. public void DoSomething(int? x)
2. {
3.    //Check if parameter has value
4.    if (x.HasValue)
5.    {
6.        //Use Value property of nullable type
7.        int y = x.Value;
8.  
9.        //Do something
10.    }
11.    else
12.    {
13.        //Do something
14.    }
15. }

User NameValueCollection or Dictionary type parameter

1. Dictionary<string, object> dict = new Dictionary<string, object>();
2. dict.Add("x",1);
3. //dict.Add("s","test");
4. DoSomething(dict);

1. public void DoSomething(Dictionary<string, object>)
2. {
3.    //Do something
4. }