Display data from database in TextBoxes based on DropDownList selection using C# and VB.Net in ASP.Net

Hi micah,

Check this example. Now please take its reference and correct your code.

Database

For this example I have used of Northwind database that you can download using the link given below.

Download Northwind Database

HTML

<asp:DropDownList ID="ddlNames" runat="server" OnSelectedIndexChanged="ddlNames_SelectedIndexChanged"
    AutoPostBack="True" AppendDataBoundItems="true">
    <asp:ListItem Value="Maria">Maria</asp:ListItem>
    <asp:ListItem Value="Ana Trujillo">Ana Trujillo</asp:ListItem>
    <asp:ListItem Value="Antonio Moreno">Antonio Moreno</asp:ListItem>
    <asp:ListItem Value="Thomas Hardy">Thomas Hardy</asp:ListItem>
</asp:DropDownList>
<br />
<asp:TextBox ID="txtId" runat="server"></asp:TextBox>
<br />
<asp:TextBox ID="txtCity" runat="server"></asp:TextBox>
<br />
<asp:TextBox ID="txtCountry" runat="server"></asp:TextBox>

Namespaces

C#

using System.Configuration;
using System.Data.SqlClient;

VB.Net

Imports System.Configuration
Imports System.Data.SqlClient

Code

C#

protected void ddlNames_SelectedIndexChanged(object sender, EventArgs e)
{
    string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {
        SqlCommand command = new SqlCommand("SELECT CustomerID,City,Country FROM Customers WHERE ContactName = @Name", con);
        command.Parameters.AddWithValue("@Name", ddlNames.SelectedItem.Text);
        con.Open();
        SqlDataReader sdr = command.ExecuteReader();
        if (sdr.Read())
        {
            txtId.Text = sdr["CustomerID"].ToString();
            txtCity.Text = sdr["City"].ToString();
            txtCountry.Text = sdr["Country"].ToString();
        }
        sdr.Close();
    }
}

VB.Net

Protected Sub ddlNames_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs)
    Dim constr As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString
    Using con As SqlConnection = New SqlConnection(constr)
        Dim command As SqlCommand = New SqlCommand("SELECT CustomerID,City,Country FROM Customers WHERE ContactName = @Name", con)
        command.Parameters.AddWithValue("@Name", ddlNames.SelectedItem.Text)
        con.Open()
        Dim sdr As SqlDataReader = command.ExecuteReader()
        If sdr.Read() Then
            txtId.Text = sdr("CustomerID").ToString()
            txtCity.Text = sdr("City").ToString()
            txtCountry.Text = sdr("Country").ToString()
        End If
        sdr.Close()
    End Using
End Sub

Screenshot