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C# Handles

Posted on 2009-07-08
Medium Priority
Last Modified: 2013-12-17
In vb it is possible to use handles to extend the use of a function/event.

I tried doing the same thing in c# and it did not work.

Here is my code.

protected void UpdateTextBoxes_Textchanged(object sender, EventArgs e)Handle Textbox1.TextChanged, TextBox2.TextChanged


But it does not work... Can anybody help?
Question by:Mr_Shaw
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LVL 21

Assisted Solution

by:Craig Wagner
Craig Wagner earned 400 total points
ID: 24804682
1. Create your event handler (which it looks like you've already done).
2. In the form designer, select one of the TextBox controls
3. Bring up the properties for Textbox1.
4. Click on the lightning bolt icon in the Property window to show the list of events.
5. In the TextChanged event, click the drop down arrow.
6. Select the existing event handler
7. Repeat steps 2 - 6 for the other TextBox controls

Accepted Solution

lppperes earned 600 total points
ID: 24804687

You have to add the handles of the TextChanged event in Form_Load, like this:
        private void Form1_Load(object sender, EventArgs e)
            textBox1.TextChanged += new EventHandler(UpdateTextBoxes_Textchanged);
            textBox2.TextChanged += new EventHandler(UpdateTextBoxes_Textchanged);

        private void UpdateTextBoxes_Textchanged(object sender, EventArgs e)
            textBox3.Text = ((TextBox)sender).Text;

Assisted Solution

Pablissimo earned 600 total points
ID: 24804701
In C# the syntax is slightly different - the += operator is overloaded to 'add' an event handler (a delegate) to an event.

In your case, somewhere in your form's constructor after InitialiseComponent is called you could use code similar to as follows:

TextBox1.TextChanged += UpdateTextBoxes_Textchanged;
TextBox2.TextChanged += UpdateTextBoxes_Textchanged;

You'll still need your Textchanged method to be implemented somewhere in the class:

protected void UpdateTextBoxes_Textchanged(object sender, EventArgs e)
// Handle the text changed here

Notice that we're not calling UpdateTextBoxes_Textchanged (no parentheses) but simply specifying that the TextChanged event of TextBox1 (and 2) should call UpdateTextBoxes_Textchanged.

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Author Comment

ID: 24804944
Here is my code... It does not do anything.
I have put breakpoints in and it never gets to the event.

    protected void btnNext_Click(object sender, EventArgs e)
    protected void updateDB()
        TextBox Comments = (TextBox)FormView1.FindControl("Textbox_Comments");
        Comments.TextChanged += UpdateTextBoxes_Textchanged;
    protected void UpdateTextBoxes_Textchanged(object sender, EventArgs e)
LVL 15

Assisted Solution

jinal earned 400 total points
ID: 24805238
1. TextChanged event is not fired for each character you enter but it fires after you lost fcous from that control.

2. Try to use ItemCreated Event of formview and use Comments.TextChanged += UpdateTextBoxes_Textchanged;

Author Comment

ID: 24805314

Author Comment

ID: 24805427
I used the event ItemCreated but It returned

Object reference not set to an instance of an object.

Author Closing Comment

ID: 31601630

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