Optional and Named Parameters in C#

Background

In prior versions of the C# Language it is necessary to the number of parameters declared in a method when the method is called, in other words it's not optional to not all the parameters of that method. Also they must be ed in the sequence they are declared for the method. In C# 4.0 however the feature "Named and Optional Arguments" has been added by which you can parameters in any sequence and also there is no need to all the parameters for that method.

So let us learn about it from the basics so beginners can also understand it.

What Optional Parameters are

An optional parameter is a parameter in a method declared with some default value. Because of the default value when we call the method there is no need to the parameter or value for that method when calling.

Key Points

An Optional Parameter must be assigned some value such as Null if it is a string and zero if it is an integer or something else depending on the type of the default value.

For example:

int a=0;
string Name="";
An Optional Parameter also allows the assignment of a value of that type instead of Null if it is string and zero if it is an integer or any other depending on that type default value.

For example:

int a=1000;
string Name="Vithal Wadje";
Optional Parameters must be declared as the last parameters with default values for the method after all the required parametes.

For example:

Public void Details(String Name,String City,String State="");//with Null

Public void Details(String Name,String City,String State="Maharashtra");//with string

Let us see the following example to learn the details.

In the preceding example the GetCustmorDetails method takes the three parametes including state that are optional parameters and when calling the GetCustmorDetails method we are just ing two parametes because state is an optional parameter and there is no need to the value for that parameter in the call of the method.

Problems Solved

It solves the problem of, when in my method there are many parameters and one of them is optional, in other words it may be ed or not ed in the call of the method. An optional parameter is useful and depending on your requirements you can use it for any purpose.

Later on we will see a realistic example of an optional parameter but let us see first about Named Parameters in C# 4.0.

What Named Parameters are in C# 4.0

Named Parameters allows the ing of parameters to a method in any sequence instead of depending on the parameter's position as declared in the method.

Key points

There is no need to follow the sequence when ing parameters to a method.
When calling a method, parameters are ed with the Parameter Name of the method.

For example:

Public void Details(String Name,String City,String State); //method

Public void Details( State:"Maharashtra" ,Name: "Vithal Wadje",City:"Latur");//ing parameters while calling method with Named Parameters

Let us see the following example to learn in detail.

In the preceding example we are ing the parameters to a method using the C# 4.0 new feature Named Parameters.

Problems Solved

In prior versions it is very difficult to remember the sequence of parameter when ing parameters to a method but in C# 4.0 you can it in any sequence and depending on your requirements you can use it for any purpose.

Now let us see the realistic example of optional and named parameters.

Create the web application as in the following:

"Start" - "All Programs" - "Microsoft Visual Studio 2010".
"File" - "New" - "Project..." then select "C#" - "Empty web site" (to avoid adding a master page).
Provide the project a name, such as "NamedandOptionalParam" or another as you wish and specify the location.
Then right-click on Solution Explorer and select "Add New Item" - "Default.aspx" page and one class file.
Drag and drop three Text Boxes and two buttons.

Then the source section of the Default.aspx page looks as in the following:

ASPX code

Now add a class by right-clicking on Solution Explorer, name it Customer.cs and add the following method.

CS code

Now call the GetCustmorDetails method in the default.aspx.cs file on button click as in the following:

Now run the application and enter values for Name and City in the text box and click on the optional button as in the following:

In the preceding example we are ing a name and city to "GetCustmorDetails" and we are not ing a state because it is optional for the method.

Now enter input in all three text boxes and click on the same optional button; the output will be as in the following:

optional output

The preceding examples show that the optional parameters may be ed or may not be ed, in other words it is not mandatory to them when calling the method.

Now Enter on the Named button with the same values as above and when ing theses values on a button click we are not following any parameter sequence but the output will be the same as we expected as in the following:

From all the examples above, I hope you understand the Named and Optional Arguments feature of C# 4.0.

Note

For detailed code please download the Zip file attached above.
A video tutorial of this article will soon be uploaded to the C# Corner video section.

Summary

We learned about the Named and Optional Arguments feature of C# 4.0, I hope this article is useful for all students and beginners. If you have any suggestion related to this article then please contact me.