regarding gui(window application)

Here is answer -

public button_click()
{
TextBox3.Text = Convert.ToInt32(TextBox1.Text) + Convert.ToInt32(TextBox2.Text);
}

Regards,

Nilesh Shah.

Hello Shanlu,

i have used C# to solve your query because u didn't mention any tags like C# or VB.NET or something anyways hers your code as per your requirement...

I feel you are a beginner so grab a good book for C# and start coding,
i have first converted the text entered into integer value and then added them displaying their result at third textbox

private void button1_Click(object sender, EventArgs e)
        {
            //i have used try catch so that if the user tries characters a message will be displayed
            try
            {
                // adding two numbers here
               int x= int.Parse(textBox1.Text) + int.Parse(textBox2.Text);
                // display result in 3rd textbox
               textBox3.Text = x.ToString(); // integer is casted to string
            }
            catch (Exception ex)
            {
//show messagebox
                MessageBox.Show("Invalid text format for addition");
                //clear the textboxes
                textBox1.Clear();
                textBox2.Clear();
            }
        }

Now if you want that in your textboxes only number must be entered then you can refer to one of my answers here
Numeric Textbox by Radix

Do rate my answer once you find it useful
Thanks & Regards
Radix :rose: