The selected value from a DropDownList to be reflected in a DataList

Question

I am trying to create a web application that will use a DropDownList to have a user choose a certain value and a DataList to show certain data. For instance, if the user selects a value from the DropDownList, only data related to the user selected value should be shown in the DataList. I am very new to ASP.NET and to C#.

The code below is what I have implemented in my code behind file. Currently I am getting an ArgumentException error I am not sure how to resolve this issue.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Data;
using System.Configuration;


public partial class Products : System.Web.UI.Page
{
    SqlDataAdapter adapter;
    DataSet dset;
    string connstring = "Data Source=(LocalDB)\v11.0;AttachDbFilename=|DataDirectory|@Registration.mdf;Integrated Security=True";
    string sql = "select * from Products";
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            adapter = new SqlDataAdapter(sql, connstring); //<--ArgumentException error occurs here
            dset = new DataSet();
            adapter.Fill(dset);
            DropDownList1.DataSource = dset.Tables[0];
            DropDownList1.DataTextField = "CategoryName";
            DropDownList1.DataValueField = "ProductID";
            DropDownList1.DataBind();
            DataListBind();
        }
    }

    protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        DataListBind();
    }
    public void DataListBind()
    {
        adapter = new SqlDataAdapter("select * from Products where ProductID=" + DropDownList1.SelectedValue + "", connstring);
        dset = new DataSet();
        adapter.Fill(dset);
        dlProducts.DataSource = dset.Tables[0];
        dlProducts.DataBind();
    }
}

@mybirthname I copied and pasted the connection string from the `Web.config` file. My connection string has a name and I tried that, and still get the same error. So instead I thought it would fix the issue by directly copying and pasting the connection string itself. — Keith Code, Dec 08 '16 at 07:38

score 0 · Answer 1 · edited May 23 '17 at 12:13

0

The problem is you connection string. If you look at the inner exception that you get it says:

Invalid value for key 'attachdbfilename'

This post is further help on this matter.

To get rid of the exception just add a @ in front of the string:

string connstring = @"Data Source=(LocalDB)\v11.0;AttachDbFilename=|DataDirectory|@Registration.mdf;Integrated Security=True";

edited May 23 '17 at 12:13

Community

1
1

answered Dec 08 '16 at 07:39

Mong Zhu

23,309
10
44
76

Nikunj Kakadiya · Answer 2 · 2016-12-08T09:48:18.053

0

You have'nt created a connection object. I think you need to create and open the connection first.

edited Dec 08 '16 at 09:48

answered Dec 08 '16 at 07:49

Nikunj Kakadiya

2,689
2
20
35

The selected value from a DropDownList to be reflected in a DataList

2 Answers2