C# - Selecting SQL Table contends into textbox : Trying to get table contents into textBoxes seperately by the prefered ID number when button_click event occours. I've found some videos about the situation but dataGrids were used in those. I'm a complete newbie in C# btw, and i'm not even sure what i'm doing.

Question is, i cant figure how to write a read-only object that is stated below in code into a textBox. I'm %90 sure that it's truly a simple thing, and i'm missing it.

    private void button2_Click(object sender, EventArgs e)
        {
            SqlCommand rcmd = new SqlCommand("SELECT ID, Column1, Column2 FROM [TEST].[dbo].[Table_1] where ID=@ID", connection);

            rcmd.Parameters.AddWithValue("@ID", textBox3.Text);
            connection.Open();
            SqlDataReader reader = rcmd.ExecuteReader();
            

            while (reader.Read())
            {
                
                //reader["Column1"] = textBox4.Text;
                //reader["Column2"] = textBox5.Text;
                
                //These wont work, says reader["Column1"] and reader["Column2"] are read-only. What to do?
            }
            connection.Close();


Lines with error are intentionally commented. No mistake there. I was trying to figure something else while keeping those in my sight.

Thanks in advance.