Appending & removing text from a TextBox

Question

I am currently working with appending text to textboxes. In a winform I have two checkboxes and one textbox. Every time a check box is checked a text appears inside the textbox. But I am having difficulties taking out the text when the checkbox is unchecked. How can append text when checkbox is checked and take out text when unchecked?

 private void checkBox1_CheckedChanged(object sender, EventArgs e)
 {
     ck = sender as CheckBox;
     if (ck != null && ck.Checked)
     {
         textBox1.AppendText(" Example1 ");
     }
     else
     {
         textBox1.AppendText("  ");
     }
 }

 private void checkBox2_CheckedChanged(object sender, EventArgs e)
 {
     ck = sender as CheckBox;
     if (ck != null && ck.Checked)
     {
         textBox1.AppendText(" Example2 ");
     }
     else
     {
         textBox1.AppendText("  ");
     }
 }

Answer 1

To take out just the text you added, you can use String.Replace :

textBox1.Text = textBox1.Text.Replace(" Example1 ", "");

Note that if the user changes the value, this text may or may not still be in the TextBox . I assume you are aware of this or this is simply an exercise.

Answer 2

Assuming you want to display :

• Example 1 when the first checkbox is checked
• Example 2 when the second is checked
• Example 1 and Example 2 if both are checked
• Empty if both are unchecked

The best is to centralize the UI logic in a single method that reflect your rules:

The approach is different as removing text I dont need. I start from an empty list and I fill it regarding the checkboxes are checked or not. Then I display it. By this way, I dont have to cope with trailing separators.

private void checkBox1_CheckedChanged(object sender, EventArgs e)
{
    UpdateTextBox();
}

private void checkBox2_CheckedChanged(object sender, EventArgs e)
{
    UpdateTextBox();
}

void UpdateTextBox()
{
    var words = new List<string>();

    if (checkbox1.Checked)
        words.Add("Example 1");

    if (checkbox2.Checked)
        words.Add("Example 2");

    textBox1.Text = string.Join(" ", words);
}

Answer 3

if (ck != null && ck.Checked)
   textBox1.Text = "Example";
else
   textBox1.Text = "";

Answer 4

Do you mean

textBox1.Text = string.Empty

Or am I missing something ?

Answer 5

Try this

 private void checkBox1_CheckedChanged(object sender, EventArgs e)
  {
        ck = sender as CheckBox;

        if (ck != null && ck.Checked)
        {
            textBox1.AppendText(" Example1 ");
        }
        else
        {
            textBox1.Text = textBox1.Text.Replace(" Example1 ", "");
        }
    }

    private void checkBox2_CheckedChanged(object sender, EventArgs e)
    {

        ck = sender as CheckBox;

        if (ck != null && ck.Checked)
        {
            textBox1.AppendText(" Example2 ");
        }
        else
        {
            textBox1.Text = textBox1.Text.Replace(" Example2 ", "");
        }
}