C# windows base this key word related and its uses in the application

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3.75/5 (4 votes)

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Hi All,
below I had given the code of C# windows base

public partial class Form1 : Form
    {
        private OleDbConnection conn = new OleDbConnection();
        private string constr = "Provider=Microsoft.Jet.OLEDB.4.0;" + "Data Source=" + System.Windows.Forms.Application.StartupPath.ToString() + @"\RFIDTEST.mdb" + ";Persist Security Info=False;";

        public Form1()
        {
            InitializeComponent();
            this.dataGridView.CellClick += new System.Windows.Forms.DataGridViewCellEventHandler(this.ck);
            conn = new OleDbConnection(constr);
            conn.Open();
            
        }

here why we put "this" key word in this line "this.dataGridView.CellClick += new System.Windows.Forms.DataGridViewCellEventHandler(this.ck);"
please help me to understand the code!

Thanks & Regards
Indrajit

Posted 5-Jun-11 23:35pm

IndrajitDasgupat

Updated 5-Jun-11 23:36pm

Toniyo Jackson

v2

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Sergey Alexandrovich Kryukov 6-Jun-11 16:05pm

I up-voted this question as I don't agree with "1"; I voted "4" (which I do very rarely on questions as most of them are "sub-standard", so this is a good mark!)
--SA

2 solutions

Solution 1

The this keyword refers to the current instance of the class. Static member functions do not have a this pointer. The this keyword can be used to access members from within constructors, instance methods, and instance accessors.

More info here[^]

Posted 5-Jun-11 23:38pm

Toniyo Jackson

Comments

Sergey Alexandrovich Kryukov 6-Jun-11 16:03pm

This is correct, my 4 (because it really needs more detailed answer, I think, when to use "this"?).
Please see my solution.
--SA

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Sergey Alexandrovich Kryukov · Accepted Answer · 2011-06-06T10:02:00

You don't need to use this in this case, but you need to be aware of it and understand what is it.

How do you think a non-static (instance) method or property access the instance members? This is because the instance method has one more "hidden" parameter which is this — a reference to the instance itself. You can explicitly use is, pretty much as if you had an explicit parameter referencing some other instance:

C#

class MyClass {
    internal MyClass(MyClass other) { this.MyMember = other.MyMember; }
    static void DemoStatic(int someParameter) {
        MyStaticMember = someParameter;
        //MyMember = ... //cannot do it, there is no "this" passed to access MyMember
    }
    int MyMember;
    static int MyStaticMember; //one per whole class, only one per AppDomain
}

In the example above you don't need this. There are cases where it is a must. It happens when one name hides identical name of the member/variable:

C#

class MyClass {
    internal MyClass(int A, int B) {
        // the name not qualified with "this" takes precedence for a parameter,
        // so a member should be qualified
        this.A = A; 
        this.B = B;
    }
    int A, B;
}

[EDIT]
The run-time type of the variable passed as this becomes fundamental to OOP: when a method is virtual, this run-type type is different from the compile-time type of it which is the type of the declaring class. This opens the road to late binding and, hence, polymorphism.

See:
http://en.wikipedia.org/wiki/Late_binding[^],
http://en.wikipedia.org/wiki/Dynamic_dispatch[^],
http://en.wikipedia.org/wiki/Polymorphism_(computer_science)[^].

Any questions?

—SA