Small Brush Up on 'IS' and 'AS' Keywords in C#.NET

Vijay Prativadi
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Today, in this article we will overlook at two main keywords i: e IS and AS functionalities and we will implement practically to understand better.

IS Keyword :

This Keyword is used to check the passed object compatibility with the give type. It evaluates the code if it is true or false and executes the expected operation.
AS Keyword:

This Keyword is used to check the compatibility with the given references types. It performs casting operation and double checks whether the passed values is null or not null. This then executes the block of code based on the decision.

Now, it's time for us to go and do some practical implementations using these keywords. Let's See how better we can implement and such that it should be also easy to understand.

Code Toolbox Requirements:

Grid View and Button

Complete Code of WebForm1.aspx looks like this:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="AS_and_IS_Keyword_Application.WebForm1" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <center>
            <asp:GridView ID="GridView1" runat="server" BackColor="White" BorderColor="#999999"
                BorderStyle="None" BorderWidth="1px" CellPadding="3" GridLines="Vertical">
                <AlternatingRowStyle BackColor="#DCDCDC" />
                <FooterStyle BackColor="#CCCCCC" ForeColor="Black" />
                <HeaderStyle BackColor="#000084" Font-Bold="True" ForeColor="White" />
                <PagerStyle BackColor="#999999" ForeColor="Black" HorizontalAlign="Center" />
                <RowStyle BackColor="#EEEEEE" ForeColor="Black" />
                <SelectedRowStyle BackColor="#008A8C" Font-Bold="True" ForeColor="White" />
                <SortedAscendingCellStyle BackColor="#F1F1F1" />
                <SortedAscendingHeaderStyle BackColor="#0000A9" />
                <SortedDescendingCellStyle BackColor="#CAC9C9" />
                <SortedDescendingHeaderStyle BackColor="#000065" />
            </asp:GridView>
            <br />
            <br />
            <asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1Click" />
        </center>
    </div>
    </form>
</body>
</html>

Complete Code of WebForm1.aspx.cs looks like this:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Data;

namespace AS_and_IS_Keyword_Application
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void PageLoad(object sender, EventArgs e)
        {

        }
        protected void Button1Click(object sender, EventArgs e)
        {
            if (Button1 is Button)
            {
                var con = new SqlConnection(@"Data Source=VIJAY-PC\SQLEXPRESS;Initial Catalog=Candidate;Integrated Security=True");
                var da = new SqlDataAdapter("Select PersonId, FirstName, LastName, Age from Student", con);
                var ds = new DataSet();
                da.Fill(ds, "s");
                GridView1.DataSource = ds;
                GridView1.DataBind();
                Button1.Visible = false;
            }
            else
            {
                Response.Write("It's Not a Button");
            }
            var y = Button1 as Button;
            Response.Write(y == null ? "Hello It's not of Type Button" : "<h1><center>Hello It's of Type Button</center></h1>");
        }
    }
}