How to display data on textbox based on selected value from dropdownlist

Question

I need data from database on my textbox when i choose the particular data in drop-down list. I do the following code but it give me the number instead of description.

int s1 = DropDownList3.SelectedIndex;

SqlCommand query = new SqlCommand("Select description from vul_auto where finding_id= " + s1,con);

TextBox3.Text =(query.ExecuteNonQuery()).ToString();

Answer 1

ExecuteNonQuery returns the number of rows affected. You would use this to do an insert/update/delete, not to select data. Instead, you should use ExecuteScalar .

Also, as a general best practice, always use parameterised queries instead of concatenating, specially when you are accepting input from user.

using (SqlConnection conn = new SqlConnection(yourconnectionstring))
{
    string sql = "Select description from vul_auto where finding_id=@id";
    SqlCommand cmd = new SqlCommand(sql, conn);
    cmd.Parameters.Add("@id", SqlDbType.Int);
    cmd.Parameters["@id"].Value = s1;
    try
    {
        conn.Open();
        TextBox3.Text = Convert.ToString(cmd.ExecuteScalar());
    }
    catch (Exception ex)
    {
        //Handle exception
    }
}

As @user3713775 mentions in his answer, use Convert.ToString to handle null values.

Answer 2

@shree.pat18 is correct. Use query.ExecuteScalar() & use ConvertToString() instead of ToString() for more robustness. like TextBox3.Text = Convert.ToString(query.ExecuteScalar());