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Constructor Chaining in C#

, 20 Oct 2011 CPOL
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Constructor Chaining is an approach where a constructor calls another constructor in the same or base class.

What is Constructor Chaining?

Constructor Chaining is an approach where a constructor calls another constructor in the same or base class.

This is very handy when we have a class that defines multiple constructors. Assume we are developing a class Student. And this class has three constructors. On each constructer we have to validate the student's ID and categorize him/her. So if we do not use the constructor chaining approach, it would be something similar to what is shown below:

screen_01_thumb_2_.png

Even though the above approach solves our problem, it duplicates code. (We are assigning a value to ‘_id’ in all our constructors). This is where constructor chaining is very useful. It will eliminate this problem. This time we only assign values in one constructor which consists of the most number of parameters. And we call that constructor when the other two constructers are called.

class Student {
    string _studentType = "";
    string _id = "";
    string _fName = "";
    string _lName = "";

    public Student(string id)
        : this(id, "", "") {

    }

    public Student(string id, string fName)
        : this(id, fName, "") {

    }

    public Student(string id, string fName, string lName) {
        //Validate logic.....
        _studentType = "<student_type>";

        _id = id;
        _fName = fName;
        _lName = lName;
    }
}

**Please note: If you do not specify anything [in this example, we used ‘this’), it will be considered that we are calling the constructor on the base class. And it’s similar to using ‘: base(…)’].

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Manjuke Fernando
Technical Lead Air Liquide Industrial Services (Singapore)
Singapore Singapore
I have been in software industry for more than 8 years. I have developed different type of software using different languages. Many of them are database related (both web & window based), SQL being as the back end most of the time. Up-to-date I have knowledge in languages such as C#, VB.Net, T-SQL, JAVA, VB6 & C++, making C# the most proficient of all. Also I have worked using different technologies like ASP.Net, SharePoint, Crystal Reports (But I really hate designing reports) & MS SQL Server and have involved in designing & developing software for major companies like FedEx, Softlogic Holdings, IronOne Technologies & Brandix. Currently I am working as a Tech Lead in Singapore.
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Comments and Discussions

 
GeneralMy vote of 4 PinmemberIakovos Karakizas22-Jan-14 23:01 
Questionuse name arguments instead PinmemberRonDsz25-Oct-11 16:23 
QuestionNot much info on "base" PinmemberRiz Thon24-Oct-11 15:41 
GeneralLike ! Pinmemberraananv24-Oct-11 12:51 
GeneralGood one.. PinmemberPritesh Aryan21-Oct-11 20:52 
GeneralMy vote of 4 PinmemberSledgeHammer0120-Oct-11 17:54 

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