C＃ExecuteReader不返回ASP.Net中的SQL查询数据

Question

I'm having trouble extracting the SQL data I need from the below query. I've looked on MSDN and followed their examples, but for some reason the executereader is not reading the data and returning it to the textbox, after clicking the button. I have added a response to ensure the connection is open, and it is each time pressed. This is an extract of the code, the only thing I have omitted from here is the sqlconnection detail:

protected void Button1_Click(object sender, EventArgs e)
{
        using (SqlConnection conn = new SqlConnection(ConnectionString))
        {

            //set up the SQL command       
            SqlCommand command = new SqlCommand("Use Waste_Test; select * from Bidston_HWRC where MCN_No = @MCN", conn);

            //open the server connection
            conn.Open();

            //define parameter for SQL query
            command.Parameters.Add("@MCN", SqlDbType.Int);
            command.Parameters["@MCN"].Value = TextBox17.Text;

            Response.Write("<script>alert('You are connected')</script>");


            //Execute the query on the server
            SqlDataReader rdr = command.ExecuteReader();

            Response.Write("<script>alert('It's worked')</script>");

            while (rdr.Read())
            {
                TextBox6.Text = rdr["Waste_Description"].ToString();
            }
        }
    }

Answer 1

first of all, you need to use HasRows in order to ensure that query return some result, if no record return then you can show a message in label. Since you are getting the MCN value from textbox, then you need to parse it into int. Try the following code.

protected void Button1_Click(object sender, EventArgs e)
{
    using (SqlConnection conn = new SqlConnection(ConnectionString))
    {     
            SqlCommand command = new SqlCommand("select * from Bidston_HWRC where MCN_No = @MCN", conn);
            conn.Open();
            Command.Parameters.AddWithValue("@MCN", Int32.Parse(TextBox17.Text));
            //Execute the query on the server
            SqlDataReader rdr = command.ExecuteReader();



        if(rdr.HasRows)
        {
            while (rdr.Read())
            {
              TextBox6.Text = rdr["Waste_Description"].ToString();
            }

        }
        else
        {
          // show 'no records found'
        }
       rdr.Close();
       conn.Close();
    }
}