I have already explained the another featire of C# 4.0 is Dynamic Programming in my previous post.
Here I am going to explain about Named and Optional Parameters.
C# 1.0, 2.0, 3.0 doest not have a feature of Optional parameter. But in VB, we can define a method with an optional parameters.
Developers facing some difficulties of not having an optional parameter in C# especially when communicating with COM object.
C# 4.0 going to have a feature of Optional Parameter.
In previous version of C#, we have to implement multiple overloaded methods to have a variable parameters in the function like
C# 3.0:
public int Add(int x, int y)
{
return x + y;
}
public int Add(int x, int y, int z)
{
return x + y + z;
}
C# 4.0 (Optional Parameter):
public int Add(int x, int y, int z = 0)
{
return x + y + z;
}
//calling
Add(1,2);
Add(1,2,3
Here we can declare the parameter as an optional by initializing the value to the variable.
if we have multiple optional parameter in a function, we have to initialize the value sequentially in VB like
VB:
Public Function Add(ByVal x As Integer, ByVal y As Integer, Optional ByVal z As Integer = 5, Optional ByVal a As Integer = 10) As Integer
Return x + y + z + a
End Function
From the above code, it has 2 optional parameter. we can't pass value to parameter "a" without passing value for parameter "z".
// Calling
Add(1, 2, 5, 15)
C# 4.0 - Named Parameter
public int Add(int x, int y, int z = 5, int a = 10)
{
return x + y + z + a;
}
//calling
Add(1,2,a:15);
From the above code, it has 2 optional parameter. But here we can pass a value to parameter "a" without passing a value for "z" by using name of parameter like a:15.
