Let's Play Around With Factory Method Design Pattern

Vijay Prativadi
Apr 23, 2012

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Introduction

Today, in this article let's play around with one of the interesting and most useful concepts of design patterns, which will be hosted in a web app.

Question: What is Factory Method Pattern?

In simple terms "An interface creates an object, but instantiation is dependent upon a child class".

I think we are now good to go to implement this wonderful concept.

Step 1: The complete code of Default.aspx looks like this:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="FactoryMethodPatternApplication._Default" %>

<!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="form2" runat="server">
    <div>
        <h1 style="text-align: center; font-family: Verdana; font-size: large; color: Maroon">
            Factory Method Pattern - Design Patterns</h1>
        <center>
            <table>
                <tr>
                    <td>
<asp:Label ID="Label1" runat="server" Text="Please Enter First Number" Font-Size="Small"
Font-Bold="true" Font-Italic="true" Font-Names="Verdana"></asp:Label>
                    </td>
                    <td>
                        <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td>
<asp:Label ID="Label2" runat="server" Text="Please Enter Second Number" Font-Size="Small" Font-Bold="true" Font-Italic="true" Font-Names="Verdana"></asp:Label>
                    </td>
                    <td>
                        <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
                    </td>
                </tr>
                <tr>
                    <td colspan="2"<asp:Button ID="Button1" runat="server" Text="Addition" Width="165px" Font-Names="Verdana"
BackColor="Orange" OnClick="Button1_Click" />
                    </td>
                </tr>
                <tr>
                    <td colspan="2"><asp:Button ID="Button2" runat="server" Text="Subtraction" Width="165px" Font-Names="Verdana"
BackColor="Orange" OnClick="Button2_Click" />
                    </td>
                </tr>
                <tr>
                    <td colspan="2">
<asp:Button ID="Button3" runat="server" Text="Multiplication" Width="165px" Font-Names="Verdana" BackColor="Orange" OnClick="Button3_Click" />
                    </td>
                </tr>
                <tr>
                    <td colspan="2">
<asp:Button ID="Button4" runat="server" Text="Division" Width="165px" Font-Names="Verdana" BackColor="Orange" OnClick="Button4_Click" />
                    </td>
                </tr>
            </table>
            <table>
                <tr>
                    <td colspan="2">
<asp:Label ID="lblResult" runat="server" Font-Names="Verdana" ForeColor="Brown"></asp:Label>
                    </td>
               </tr>
            </table>
        </center>
    </div>
    </form>
</body>
</html>

Step 2: The complete code of IAdd.cs looks like this:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;namespace FactoryMethodPatternApplication

{

public interface IAdd{double Add(double a, double b);}

}

Step 3: The complete code of ISub.cs looks like this:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;namespace FactoryMethodPatternApplication

{

public interface ISub{double Sub(double a, double b);}

}

Step 4: The complete code of IMul.cs looks like this:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;namespace FactoryMethodPatternApplication

{

public interface IMul{double Mul(double a, double b);}

}

Step 5: The complete code of IDiv.cs looks like this:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;namespace FactoryMethodPatternApplication

{

public interface IDiv{double Div(double a, double b);}

}

Step 6: The complete code of ClassAdd.cs looks like this:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;namespace FactoryMethodPatternApplication

{

public class ClassAdd:IAdd{public double Add(double a, double b){return a + b;}}

}

Step 7: The complete code of ClassSub.cs looks like this:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;namespace FactoryMethodPatternApplication

{

public class ClassSub:ISub{public double Sub(double a, double b){return a - b;}}

}

Step 8: The complete code of ClassMul.cs looks like this:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;namespace FactoryMethodPatternApplication

{

public class ClassMul:IMul{public double Mul(double a, double b){return a * b;}}

}

Step 9: The complete code of ClassDiv.cs looks like this:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;namespace FactoryMethodPatternApplication

{

public class ClassDiv:IDiv{public double Div(double a, double b){return a / b;}}

}

Step 10: The complete code of IFactoryMethodArthmetic.cs looks like this:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;namespace FactoryMethodPatternApplication

{

public interface IFactoryMethodArthmetic{IAdd Add();ISub Sub();IMul Mul();IDiv Div();}

}

Step 11: The complete code of FactoryMethodArthmetic.cs looks like this:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;namespace FactoryMethodPatternApplication

{

public class FactoryMethodArthmetic:IFactoryMethodArthmetic{public IAdd Add(){return new ClassAdd();}public ISub Sub(){return new ClassSub();}public IMul Mul(){return new ClassMul();}public IDiv Div(){return new ClassDiv();}}

}

Step 12: The complete code of Default.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 FactoryMethodPatternApplication

{

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

{

protected void Page_Load(object sender, EventArgs e)

{

}

public void Button1_Click(object sender, EventArgs e)

{ AddData();

}

public void Button2_Click(object sender, EventArgs e) { SubData();

}

public void Button3_Click(object sender, EventArgs e)

{

MulData();

}

public void Button4_Click(object sender, EventArgs e)

{

DivData();

}

public void AddData()

{

if (string.IsNullOrEmpty(TextBox1.Text) || string.IsNullOrEmpty(TextBox2.Text))

{

lblResult.Text = "Please Enter Some Values";

}

else

{

IFactoryMethodArthmetic objArthmetic = new FactoryMethodArthmetic(); IAdd addFactory; addFactory = objArthmetic.Add(); lblResult.Text = "Addition Result of " + TextBox1.Text + " and " + TextBox2.Text + " is: <b>" + addFactory.Add(Convert.ToDouble(TextBox1.Text), Convert.ToDouble(TextBox2.Text)) + "</b>"; TextBox1.Text = ""; TextBox2.Text = "";

}

} public void SubData()

{

if (string.IsNullOrEmpty(TextBox1.Text) || string.IsNullOrEmpty(TextBox2.Text))

{

lblResult.Text = "Please Enter Some Values";

}

else

{ IFactoryMethodArthmetic objArthmetic = new FactoryMethodArthmetic(); ISub subFactory; subFactory = objArthmetic.Sub(); lblResult.Text = "Subtraction Result of " + TextBox1.Text + " and " + TextBox2.Text + " is: <b>" + subFactory.Sub(Convert.ToDouble(TextBox1.Text), Convert.ToDouble(TextBox2.Text)) + "</b>"; TextBox1.Text = ""; TextBox2.Text = "";

}

} public void MulData()

{

if (string.IsNullOrEmpty(TextBox1.Text) || string.IsNullOrEmpty(TextBox2.Text)) { lblResult.Text = "Please Enter Some Values";

}

else

{

IFactoryMethodArthmetic objArthmetic = new FactoryMethodArthmetic(); IMul mulFactory; mulFactory = objArthmetic.Mul(); lblResult.Text = "Multiplication Result of " + TextBox1.Text + " and " + TextBox2.Text + " is: <b>" + mulFactory.Mul(Convert.ToDouble(TextBox1.Text), Convert.ToDouble(TextBox2.Text)) + "</b>"; TextBox1.Text = ""; TextBox2.Text = "";

}

public void DivData()

{

if (string.IsNullOrEmpty(TextBox1.Text) || string.IsNullOrEmpty(TextBox2.Text)) { lblResult.Text = "Please Enter Some Values";

}

else

{

IFactoryMethodArthmetic objArthmetic = new FactoryMethodArthmetic(); IDiv divFactory; divFactory = objArthmetic.Div(); lblResult.Text = "Division Result of " + TextBox1.Text + " and " + TextBox2.Text + " is: <b>" + divFactory.Div(Convert.ToDouble(TextBox1.Text), Convert.ToDouble(TextBox2.Text)) + "</b>"; TextBox1.Text = ""; TextBox2.Text = "";

}

Step 13: The output of the application looks like this: