Question

I have tried this code to add from textbox1.text and textbox2.text into textbox3.text

private void textBox1_TextChanged(object sender, EventArgs e)
    {
        if(!string.IsNullOrEmpty(textBox1.Text) || string.IsNullOrEmpty(textBox2.Text))

         { 
             textBox3.Text = (Convert.ToInt32(textBox1.Text) + Convert.ToInt32(textBox2.Text).ToString());
         }
    }

    private void textBox2_TextChanged(object sender, EventArgs e)
    {
        if(!string.IsNullOrEmpty(textBox1.Text) || string.IsNullOrEmpty(textBox2.Text))

        {
        textBox3.Text = (Convert.ToInt32(textBox1.Text) + Convert.ToInt32(textBox2.Text).ToString());
        }
    }

please Help … and is there anything like to change ‘format ‘property of textbox to general number?

Answer 1

You made a mistake || should be replace with && so it will check both the text boxes are filled with value.

You have used .ToString() method wrongly which applies only to textbox2, check the brackets properly.

textBox3.Text = (Convert.ToInt32(textBox1.Text) + Convert.ToInt32(textBox2.Text).ToString());

should be

textBox3.Text = (Convert.ToInt32(textBox1.Text) + Convert.ToInt32(textBox2.Text)).ToString();

Try This Tested Code.

 private void textBox1_TextChanged(object sender, EventArgs e)
 {
  if (!string.IsNullOrEmpty(textBox1.Text) && !string.IsNullOrEmpty(textBox2.Text))
  textBox3.Text = (Convert.ToInt32(textBox1.Text) + Convert.ToInt32(textBox2.Text)).ToString();
 }
    
 private void textBox2_TextChanged(object sender, EventArgs e)
 {
  if (!string.IsNullOrEmpty(textBox1.Text) && !string.IsNullOrEmpty(textBox2.Text))
  textBox3.Text = (Convert.ToInt32(textBox1.Text) + Convert.ToInt32(textBox2.Text)).ToString();
 }