Drop down list index changing displaying error Incorrect syntax near '='

[silwar]

Hi,

I have already stored value of author id in list item value while page loads. but when I change index of drop down list to view author information error is shown. I tried to debug using check points and it seems Sqlreader isn't reading database second time.

Incorrect syntax near '='..

Here is my code

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Web;
using System.Web.Configuration;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Text;
 
public partial class retrieverecord : System.Web.UI.Page
{
    private string connString = WebConfigurationManager.ConnectionStrings["Pubs"].ConnectionString;
 
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!this.IsPostBack)
        {
            FillAuthor();
        }
    }
    private void FillAuthor()
    {
        ddList.Items.Clear();
 
     //Define the select statement, 3 pieces of info 
     //namely the unique id and first and last name of suthor
 
        string selectSQL = "SELECT au_lname, au_fname, au_id FROM Authors";
 
    // Define the ADO objects
        SqlConnection cn = new SqlConnection(connString);
        SqlCommand cmd = new SqlCommand(selectSQL, cn);
        SqlDataReader reader;
 
 
    //try to open database and read info.
 
        try
        {
            cn.Open();
            reader = cmd.ExecuteReader();
            while (reader.Read())
            {
 
                ListItem newItem = new ListItem();
                newItem.Text = reader["au_lname"] + ", " + reader["au_fname"];
                newItem.Value = reader["au_id"].ToString();
                ddList.Items.Add(newItem);
            }
            reader.Close();
        }
        catch (Exception err)
        {
            lblResult.Text = "Error reading list of names.";
            lblResult.Text += err.Message;
        }
        finally
        {
            cn.Close();
        }
    }
 
    // Every time index is changed data will be reloaded.
    protected void ddList_SelectedIndexChanged(object sender, EventArgs e)
    {
    //Create a Select statement that searches for a record
    //Matching the specific author ID from the Value property
 
        string SQLselect;
        SQLselect = "SELECT * FROM authors";
        SQLselect += "WHERE au_id='"+ddList.SelectedItem.Value+"'";
 
     //Define the ADO.NET objects
 
        SqlConnection con = new SqlConnection(connString);
        SqlCommand cmd = new SqlCommand(SQLselect,con);
        SqlDataReader reader;
 
     //try to open database and read information.
        try
        {
            con.Open();
            reader = cmd.ExecuteReader();
            reader.Read();
 
        //Fill the Control
 
            txtBox1.Text = reader["au_ID"].ToString();
            txtBox2.Text = reader["au_fname"].ToString();
            txtBox3.Text = reader["au_lname"].ToString();
            txtBox4.Text = reader["phone"].ToString();
            txtBox5.Text = reader["address"].ToString();
            txtBox6.Text = reader["city"].ToString();
            txtBox7.Text = reader["state"].ToString();
            txtBox8.Text = reader["zip"].ToString();
 
            chkContract.Checked = (bool)reader["contract"];
 
            lblResult.Text = "";
 
            reader.Close();
        }
        catch (Exception err)
        {
            lblResult.Text = "Error getting author.<br />";
            lblResult.Text += err.Message;
        }
        finally
        {
            con.Close();
        }
 
 
    }
}

when I debug error is shown. Please take a look and help.

[VijaySofist]

Hi,

Check the DataSource using If Condition and Give all the SelectedIndex Code there

For Example

if ((ddList.DataSource != null)) {
//Your Code Here
}

If this does not solve your problem, take a screenshot of that error & give here

All the Best

Regards
Vijay.R

[silwar]

Well i found the problem. it was select statement string
i.e.

thats how I created string

string selSQL;
        selSQL = "SELECT * FROM authors";
        selSQL += "WHERE au_id=@value";

This one works

selSQL = "SELECT * FROM authors WHERE au_id=@value";

I think while declaring string for command object we can't append it with other string it need to be declared in a single line

also i learned about parameters

Thanks for your reply Vijay