In this article I will explain with an example, how to filter the items in DataList control based on the selected value in DropDownList control in ASP.Net using C# and VB.Net.
 
 

Database

Here I am making use of Microsoft’s Northwind Database. You can download it from here.
Download and install Northwind Database
 
 

HTML Markup

The following HTML Markup consists of:
DropDownList – For displaying countries.
The DropDownList consists of ListItem.
 
DataList – For displaying data.
The DataList consists of ItemTemplate which contains Eval function to bind columns from database.
Country:
<asp:DropDownList ID="ddlCountry" AutoPostBack="true" runat="server">
    <asp:ListItem Text="All" Value="" />
    <asp:ListItem Text="Argentina" Value="Argentina" />
    <asp:ListItem Text="Belgium" Value="Belgium" />
    <asp:ListItem Text="Brazil" Value="Brazil" />
    <asp:ListItem Text="Canada" Value="Canada" />
</asp:DropDownList><br />
<asp:DataList ID="dlCustomers" runat="server" RepeatLayout="Table" RepeatColumns="3" CellPadding="2" CellSpacing="2">
    <ItemTemplate>
        <table cellpadding="2" cellspacing="0" border="1" style="width: 200px; height: 100px; border: dashed 2px #F7F7F7; background-color: #F7F7F7">
            <tr>
                <td>
                    <b><u><span class="name"><%# Eval("ContactName") %></span></u></b>
                </td>
            </tr>
            <tr>
                <td>
                    <b>City: </b><span class="city"><%# Eval("City") %></span><br />
                    <b>Postal Code: </b><span class="postal"><%# Eval("PostalCode") %></span><br />
                    <b>Country: </b><span class="country"><%# Eval("Country")%></span><br />
                    <b>Phone: </b><span class="phone"><%# Eval("Phone")%></span><br />
                    <b>Fax: </b><span class="fax"><%# Eval("Fax")%></span><br />
                </td>
            </tr>
        </table>
    </ItemTemplate>
</asp:DataList>
 
 

Namespaces

You will need to import the following namespaces.
C#
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
 
VB.Net
Imports System.Data
Imports System.Data.SqlClient
Imports System.Configuration
 
 

Binding and Filtering the Items of the ASP.Net DataList Control

Inside the Page_Load event handler, the records are fetched from the Customers Table of the Northwind database.
Then, a DropDownList’s Country parameter is added to a SqlCommand.
Finally, Dataset is assigned to the DataSource property of the Dataset and the Dataset is populated.
C#
protected void Page_Load(object sender, EventArgs e)
{
    string sql = "SELECT ContactName, City, PostalCode, Country, Phone, Fax FROM Customers WHERE Country=@Country or @Country=''";
    string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {
        using (SqlCommand cmd = new SqlCommand(sql, con))
        {
            using (SqlDataAdapter sda = new SqlDataAdapter(cmd))
            {
                cmd.Parameters.AddWithValue("@Country", ddlCountry.SelectedItem.Value);
                using (DataSet ds = new DataSet())
                {
                    sda.Fill(ds);
                    dlCustomers.DataSource = ds;
                    dlCustomers.DataBind();
                }
            }
        }
    }
}
 
VB.Net
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    Dim sql As String = "SELECT ContactName, City, PostalCode, Country, Phone, Fax FROM Customers WHERE Country=@Country or @Country=''"
    Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Using con As SqlConnection = New SqlConnection(constr)
        Using cmd As SqlCommand = New SqlCommand(sql, con)
            Using sda As SqlDataAdapter = New SqlDataAdapter(cmd)
                cmd.Parameters.AddWithValue("@Country", ddlCountry.SelectedItem.Value)
                Using ds As DataSet = New DataSet()
                    sda.Fill(ds)
                    dlCustomers.DataSource = ds
                    dlCustomers.DataBind()
                End Using
            End Using
        End Using
    End Using
End Sub
 
 

Screenshot

Filter Items (records) in ASP.Net DataList based on the selected value in DropDownList
 
 

Demo

View Demo
 
 

Downloads

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