Fetch and Display value from Database based on ASP.Net DropDownList selection using C# and VB.Net

Hey dorsa,

Please refer below smaple.

Use equal operator insted of like operator.

HTML

<div>
    <asp:DropDownList runat="server" ID="ddlName">
        <asp:ListItem Text="Mathematics" />
        <asp:ListItem Text="Mathematics2" />
        <asp:ListItem Text="literature" />
        <asp:ListItem Text="literature2" />
    </asp:DropDownList>
    <asp:Button Text="Submit" runat="server" OnClick="Submit" />
    <asp:Label ID="LblLessonId" runat="server" />
</div>

Namespaces

C#

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

VB.Net

Imports System.Data.SqlClient

Code

C#

protected void Submit(object sender, EventArgs e)
{
    using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["constr"].ConnectionString))
    {
        using (SqlCommand cmd = new SqlCommand("select CustomerId from Customers WHERE Name = '" + ddlName.SelectedItem.Text + "'", con))
        {
            SqlDataReader dr;
            con.Open();
            dr = cmd.ExecuteReader();
            if (dr.Read())
            {
                LblLessonId.Text = dr["CustomerId"].ToString();
            }
            con.Close();
        }
    }
}

VB.Net

Protected Sub Submit(ByVal sender As Object, ByVal e As EventArgs)
    Using con As SqlConnection = New SqlConnection(ConfigurationManager.ConnectionStrings("constr").ConnectionString)
        Using cmd As SqlCommand = New SqlCommand("select CustomerId from Customers WHERE Name = '" + ddlName.SelectedItem.Text + "'", con)
            Dim dr As SqlDataReader
            con.Open()
            dr = cmd.ExecuteReader()
            If dr.Read() Then
                LblLessonId.Text = dr("CustomerId").ToString()
            End If
            con.Close()
        End Using
    End Using
End Sub

Screenshot