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Question

how to do this: i press 'G' on textbox and i'll see 'A' ?

Answer 1

+4 A:

I think you should handle the KeyPress event. Check if the key pressed is G, if yes, reject the input and put A in the textbox. Try this (The character will be appended to existing text:

    private void textBox1_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e)
    {
        if (e.KeyChar == 'G')
        {
            // Stop the character from being entered into the control
            e.Handled = true;
            textBox1.Text += 'A';
        }
    }

Sidharth Panwar 2010-09-14 07:05:25

Instead of `textBox1.Text += 'A';` i would prefer `textBox1.AppendText("A");`

Oliver 2010-09-14 11:45:16

@Oliver Any specific reason?

Sidharth Panwar 2010-09-14 14:24:34

@Sidharth: Performance. Just put 10,000 chars into your textBox and let a timer add a random char every 100ms. In the first test use the `+=` approach. In the second the `AppendText()` solution. The problem is that a string is immutable and so the whole string will be taken out of the textbox a single char appended and this whole string will be given back to the TextBox. This tells the Box to throw away its whole content and take the new one, thous leading to nasty flickering.

Oliver 2010-09-15 09:14:57

Wouldn't there be better my approach?

Juan Nunez 2010-09-15 09:26:28

Answer 2

+12 A:

    TextBox t = new TextBox();
    t.KeyPress += new KeyPressEventHandler(t_KeyPress);


    void t_KeyPress(object sender, KeyPressEventArgs e)
    {
        if (e.KeyChar == 'G')
            e.KeyChar = 'A';
    }

Juan Nunez 2010-09-14 07:06:23

This is more elegant :) - +1

Sidharth Panwar 2010-09-14 07:09:23

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how to do this: i press 'G' on textbox and i'll see 'A' ?

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