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Out Keyword in C#

Posted by Vijay Prativadi Blogs | Visual C# Oct 12, 2012
Today, in this blog let’s play around with one of the interesting and most useful concept in C#.

Out Keyword in C#

 

Introduction

 

Today, in this article let's play around with one of the interesting and most useful concept in C#.

 

Question: What is out keyword?

 

In simple terms "The out keyword causes arguments to be passed by reference. This is similar to the ref keyword, except that ref requires that the variable be initialized before being passed."

 

Step 1: Create a new webform project

 

pic1.png
 

Step 2: The complete code of webform1.aspx looks like this

 

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

 

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">

<head id="Head1" runat="server">

    <title></title>

</head>

<body>

    <form id="form2" runat="server">

    <center>

        <div>

            <table>

                <tr>

                    <td colspan="2" align="center">

                        <asp:Label ID="Label1" runat="server" Text="Out Keyword in C#" Font-Bold="true" Font-Size="Large"

                            Font-Names="Verdana" ForeColor="Maroon"></asp:Label>

                    </td>

                </tr>

                <tr>

                    <td>

                        <asp:Label ID="Label6" runat="server" Text="Please Enter FirstNumber" Font-Size="Large"

                            Font-Names="Verdana" Font-Italic="true"></asp:Label>

                    </td>

                    <td>

                        <asp:TextBox ID="TextBox4" runat="server"></asp:TextBox>

                    </td>

                </tr>

                <tr>

                    <td>

                        <asp:Label ID="Label2" runat="server" Text="Please Enter SecondNumber" Font-Size="Large"

                            Font-Names="Verdana" Font-Italic="true"></asp:Label>

                    </td>

                    <td>

                        <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>

                    </td>

                </tr>

                <tr>

                    <td colspan="2" align="center">

                        <asp:Button ID="Button1" runat="server" Text="Addition" Font-Names="Verdana" Width="213px"

                            BackColor="Orange" Font-Bold="True" OnClick="Button1_Click" />

                    </td>

                </tr>

                <tr>

                    <td colspan="2" align="center">

                        <asp:Button ID="Button2" runat="server" Text="Substraction" Font-Names="Verdana"

                            Width="213px" BackColor="Orange" Font-Bold="True" OnClick="Button2_Click" />

                    </td>

                </tr>

                <tr>

                    <td colspan="2" align="center">

                        <asp:Button ID="Button3" runat="server" Text="Multiplication" Font-Names="Verdana"

                            Width="213px" BackColor="Orange" Font-Bold="True" OnClick="Button3_Click" />

                    </td>

                </tr>

                <tr>

                    <td colspan="2" align="center">

                        <asp:Button ID="Button4" runat="server" Text="Division" Font-Names="Verdana" Width="213px"

                            BackColor="Orange" Font-Bold="True" OnClick="Button4_Click" />

                    </td>

                </tr>

                <tr>

                    <td colspan="2" align="center">

                        <asp:Label ID="Label5" runat="server" Font-Bold="true" Font-Names="Verdana"></asp:Label>

                    </td>

                </tr>

            </table>

        </div>

    </center>

    </form>

</body>

</html>

 

Step 3: The 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;

namespace OutKeywordApp

{

    public partial class WebForm1 : System.Web.UI.Page

    {

        protected void Page_Load(object sender, EventArgs e)

        {

            TextBox4.Focus();

        }

        protected void Button1_Click(object sender, EventArgs e)

        {

            double a;

            double b;

            if (string.IsNullOrEmpty(TextBox4.Text) || string.IsNullOrEmpty(TextBox1.Text))

            {

                Label5.Text = "Please Enter Some Values";

                Label5.ForeColor = System.Drawing.Color.Red;

            }

            else

            {

                Label5.Text = "Addition Result is: " + Add(out a, out b);

                Label5.ForeColor = System.Drawing.Color.Green;

                TextBox4.Text = string.Empty;

                TextBox1.Text = string.Empty;

            }

        }

        protected void Button2_Click(object sender, EventArgs e)

        {

            double a;

            double b;

            if (string.IsNullOrEmpty(TextBox4.Text) || string.IsNullOrEmpty(TextBox1.Text))

            {

                Label5.Text = "Please Enter Some Values";

                Label5.ForeColor = System.Drawing.Color.Red;

            }

            else

            {

                Label5.Text = "Substraction Result is: " + Sub(out a, out b);

                Label5.ForeColor = System.Drawing.Color.Green; TextBox4.Text = string.Empty;

                TextBox1.Text = string.Empty;

            }

        }

        protected void Button3_Click(object sender, EventArgs e)

        {

            double a;

            double b;

            if (string.IsNullOrEmpty(TextBox4.Text) || string.IsNullOrEmpty(TextBox1.Text))

            {

                Label5.Text = "Please Enter Some Values";

                Label5.ForeColor = System.Drawing.Color.Red;

            }

            else

            {

                Label5.Text = "Multiplication Result is: " + Mul(out a, out b);

                Label5.ForeColor = System.Drawing.Color.Green;

                TextBox4.Text = string.Empty;

                TextBox1.Text = string.Empty;

            }

        }

        protected void Button4_Click(object sender, EventArgs e)

        {

            double a;

            double b;

            if (string.IsNullOrEmpty(TextBox4.Text) || string.IsNullOrEmpty(TextBox1.Text))

            {

                Label5.Text = "Please Enter Some Values";

                Label5.ForeColor = System.Drawing.Color.Red;

            }

            else

            {

                Label5.Text = "Division Result is: " + Div(out a, out b);

                Label5.ForeColor = System.Drawing.Color.Green;

                TextBox4.Text = string.Empty; TextBox1.Text = string.Empty;

            }

        }

        protected double Add(out double a, out double b)

        {

            a = double.Parse(TextBox4.Text);

            b = double.Parse(TextBox1.Text);

            return a + b;

        }

        protected double Sub(out double a, out double b)

        {

            a = double.Parse(TextBox4.Text);

            b = double.Parse(TextBox1.Text);

            return a - b;

        }

        protected double Mul(out double a, out double b)

        {

            a = double.Parse(TextBox4.Text);

            b = double.Parse(TextBox1.Text);

            return a * b;

        }

        protected double Div(out double a, out double b)

        {

            a = double.Parse(TextBox4.Text);

            b = double.Parse(TextBox1.Text);

            return a / b;

        }

    }

}

 

Step 4: The output of the application looks like this

 

Output2.png

 

Step 5: The addition operation output of the application looks like this

  Output3.png

I hope this article is useful for you ...I look forward for your comments and feedback....Thanks Vijay Prativadi

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