C# 4.0: Optional and Named Parameters - CTP Release

C# Chief Architect Anders Hejlsberg explained the future of C# in PDC2008.Initial CTP release of C# 4.0 has a feature of Optional and Named Parameters.

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.

C# 4.0 : Dynamic Programming -- CTP Release

C# Chief Architect Anders Hejlsberg explained the future of C# in PDC2008.Initial CTP release of C# 4.0 has some features like

1. Dynamically Typed Objects.
2. Optional and Named Parameters
3. Improved COM Interoperability.
4. Co and Contra Variance.

Here I am going to explain about Dynamic Programming.

Dynamically Typed Objects:

Here is the code for traditional way of calling typed object methods.

EmployeeInfo eInfo = new EmployeeInfo();
eInfo.EmployeeID = 1;
eInfo.FirstName = "Ayyanar";
eInfo.LastName = "Jayabalan";

Employee emp = GetEmployee();
bool affected = emp.AddEmployee(eInfo);

From the above code, we know the type "Employee" to call the AddEmployee methods.

if we does not know the Type("Employee"), we can use Reflection to call the AddEmployee method.

Here is the code to call the method using Reflection.

object refEmp = GetEmployee();

Type type = refEmp.GetType();

object objAffected = type.InvokeMember("AddEmployee", System.Reflection.BindingFlags.InvokeMethod, null, null, new object[] { eInfo });

bool affected = (bool)objAffected;

C# 4.0:
-------

We can call method directly without using Reflection for UnKnown Typed object.

dynamic emp = GetEmployee();

bool affected = emp.AddEmployee(eInfo);

We have to declared as a "dynamic" for unknown typed objects.

Method calling decision taken at RUNTIME instead of COMPILE TIME.

And also, .Net does not throw error while compiling the code and does not provide INTELLISENSE for dynamic type.

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Visual Studio 2010 and Framework 4.0 - CTP Release

Microsoft released the CTP version of Visual Studio 2010 and Framework 4.0.

Here is the link to download. http://www.microsoft.com/downloads/details.aspx?FamilyId=922B4655-93D0-4476-BDA4-94CF5F8D4814&displaylang=en