Show Hide ASP.Net UserControl based on condition using C# and VB.Net

Hi ramco1917,

Please refer below sample.

Database

I have made use of the following table Customers with the schema as follows. 

I have already inserted few records in the table.

You can download the database table SQL by clicking the download link below.

Download SQL file

User Control

<%@ Control Language="C#" AutoEventWireup="true" CodeFile="WebUserControl.ascx.cs"
    Inherits="WebUserControl" %>
<asp:Label ID="lblCountry" runat="server">Welcome to ASPSnippets.</asp:Label>

HTML

<%@ Register Src="~/WebUserControl.ascx" TagPrefix="uc" TagName="MyControl" %>

<asp:DropDownList ID="ddlCountries" runat="server" OnSelectedIndexChanged="OnSelectedIndexChanged"
    AutoPostBack="true">
</asp:DropDownList>
<hr />
<uc:MyControl ID="ucMyControl" runat="server" Visible="false" />

Namespaces

C#

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

VB.Net

Imports System.Data
Imports System.Configuration
Imports System.Data.SqlClient

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        string conString = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
        using (SqlConnection con = new SqlConnection(conString))
        {
            using (SqlCommand cmd = new SqlCommand("SELECT * FROM Customers", con))
            {
                con.Open();
                ddlCountries.DataSource = cmd.ExecuteReader();
                ddlCountries.DataTextField = "Name";
                ddlCountries.DataValueField = "Country";
                ddlCountries.DataBind();
                con.Close();
            }
        }
    }
}

protected void OnSelectedIndexChanged(object sender, EventArgs e)
{
    if (ddlCountries.SelectedItem.Value == "India")
    {
        ucMyControl.Visible = true;
    }
    else
    {
        ucMyControl.Visible = false;
    }
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Dim conString As String = ConfigurationManager.ConnectionStrings("constr").ConnectionString

        Using con As SqlConnection = New SqlConnection(conString)

            Using cmd As SqlCommand = New SqlCommand("SELECT * FROM Customers", con)
                con.Open()
                ddlCountries.DataSource = cmd.ExecuteReader()
                ddlCountries.DataTextField = "Name"
                ddlCountries.DataValueField = "Country"
                ddlCountries.DataBind()
                con.Close()
            End Using
        End Using
    End If
End Sub

Protected Sub OnSelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs)
    If ddlCountries.SelectedItem.Value = "India" Then
        ucMyControl.Visible = True
    Else
        ucMyControl.Visible = False
    End If
End Sub

Screenshot