confused with args for event handler~

This is a discussion on confused with args for event handler~ within the C# Programming forums, part of the General Programming Boards category; howdy~ i'm go my first step on C# on a small asp.net app. i found a tuto very useful and ...

  1. #1
    flashing vampire black's Avatar
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    confused with args for event handler~

    howdy~

    i'm go my first step on C# on a small asp.net app. i found a tuto very useful and most of its code are neat and nice, but i really get confused on args for even handler, the code of hanlder is somewhawt like this below:
    Code:
    void EnterBtn_Click(Object Src, EventArgs E) {
                Message.Text = "Hello " + Name.Text + ", welcome to world of ASP.NETŁĄ";
            }
    what about that object and eventargs there ???

    thanx~
    Never end on learning~

  2. #2
    the hat of redundancy hat nvoigt's Avatar
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    Thats more of a definition than a real coding issue. A well-formed Event-Handler always has two parameters:

    object sender
    EventArgs e

    Depending on the event it is handling, the handler might receive classes derived from EventArgs like MouseEventArgs for Mouse events or any other class. The object always contains the instance of a class that caused the event. For example if you have a button clicked event, the first parameter given will always be the button in question. This way you can write a single eventhandler for many buttons and still know which one was pressed. The second parameter contains all additional info. For Mouse events, you can get the current mouse coordinates and button states from the second parameter.
    hth
    -nv

    She was so Blonde, she spent 20 minutes looking at the orange juice can because it said "Concentrate."

    When in doubt, read the FAQ.
    Then ask a smart question.

  3. #3
    flashing vampire black's Avatar
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    thanx nvoigt~

    but i also failed when i try to reference Src like this:
    Code:
    void EnterBtn_Click(Object Src, EventArgs E) {
                Message.Text = "Hello " + Name.Text + ", welcome to world of ASP.NETŁĄ";
                Src.Text = "fsdfs";
    }
    what's wrong here ???
    Last edited by black; 03-02-2004 at 11:10 PM.
    Never end on learning~

  4. #4
    the hat of redundancy hat nvoigt's Avatar
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    While you know that the sender must be a button and therefore have a text, your compiler does not. For the compiler, it is an object and objects don't have a Text property. You have to cast it to a button:

    (Sender as Button).Text = ...
    hth
    -nv

    She was so Blonde, she spent 20 minutes looking at the orange juice can because it said "Concentrate."

    When in doubt, read the FAQ.
    Then ask a smart question.

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