C＃数据库检索

Question

Again I can't get the answer for my query. I have written the code to retrieve the data from the database and load it into a textbox by selecting the dropdown list. If I have selected my data in dropdown list it will not give the answer exactly, instead it'll show selected index 0. I mean it'll show "-Select-". there is nothing done into the textbox. I have checked my asp page for OnSelectedIndex and AutoPostBack=True. Please correct me.. Here is my code:

//This is for retrieval of data to dropdown list.
 public void engi()
    {
        DropDownList1.Items.Clear();
        ListItem l = new ListItem();
        l.Text = "-Select-";
        DropDownList1.Items.Add(l);
        DropDownList1.SelectedIndex = 0;
        Conhr.Open();
        SqlCommand cmd = new SqlCommand("select EmployeeName from tbl_EmploeeDetails where Designation like('%Engineer') ", Conhr);
        //SqlCommand cmd=new SqlCommand("select  Sitecode from MRsite where Sitealiasname in (select Componetcode from tbl_Component where Sitecode='" + TextBox1.Text.Trim() + "'");
        SqlDataReader dr;
        dr = cmd.ExecuteReader();
        while (dr.Read())
        {
            ListItem n = new ListItem();
            n.Text = dr["EmployeeName"].ToString().Trim();
            DropDownList1.Items.Add(n);
        }
        dr.Close();
        Conhr.Close();
    }

//This is for retrieval data for text box by selecting DropDown List
 public void des()
    {
        Conhr.Open();
        string s3;
        s3 = "select Designation from tbl_EmploeeDetails where EmployeeName='" + DropDownList1.SelectedItem.Text + "'";
        SqlCommand c3 = new SqlCommand(s3, Conhr);
        SqlDataReader d3;
        d3 = c3.ExecuteReader();
        while (d3.Read())
        {
            TextBox1.Text = d3["Designation"].ToString().Trim();

        }
        d3.Close();
        Conhr.Close();
    }
//Called the method for data retrieval for Textbox

 protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        des();

    }

Answer 1

I'm glad that you've posted your code (good!) - but we need more information.

SUGGESTION:

1) query your database directly (eg using the MSSQL GUI). Find a "select" statement that works.

2) step into the debugger. Print your SQL (eg "s3") just before you query.

3) compare the "good query" with the "failing" query.

The problem could be as simple as a spelling error:

-- Maybe you meant "tbl_EmployeeDetails" here?
s3 = 
  "select Designation from tbl_EmploeeDetails where EmployeeName='" +       
  DropDownList1.SelectedItem.Text + "'";