Display user id from database in JavaScript popup using C# and VB.Net in ASP.Net

Hi indradeo,

Check this sample. now take its reference.

HTML

<script type="text/javascript">
    window.onload = function () {
        var userId = document.getElementById("lblUserID").innerHTML;
        alert('User ID is ' + userId);
    }
</script>
<form id="form1" runat="server">
<div>
    <asp:Label ID="lblUserID" Text="" runat="server" Style="display: none" />
</div>
</form>

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["constr"].ConnectionString))
        {
            using (SqlCommand cmd = new SqlCommand("SELECT UserID FROM Users WHERE UserName='Test' AND Password='pass'", con))
            {
                cmd.CommandType = CommandType.Text;
                con.Open();
                int UserID = Convert.ToInt32(cmd.ExecuteScalar());
                con.Close();
                lblUserID.Text = UserID.ToString();
            }
        }
    }
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
    If Not Me.IsPostBack Then

        Using con As SqlConnection = New SqlConnection(ConfigurationManager.ConnectionStrings("constr").ConnectionString)

            Using cmd As SqlCommand = New SqlCommand("SELECT UserID FROM Users WHERE UserName='Test' AND Password='pass'", con)
                cmd.CommandType = CommandType.Text
                con.Open()
                Dim UserID As Integer = Convert.ToInt32(cmd.ExecuteScalar())
                con.Close()
                lblUserID.Text = UserID.ToString()
            End Using
        End Using
    End If
End Sub

Screenshot