Technical Blog: How to create DLL in asp.net(C#)

Steps to create DLL (Dynamic Linking Library)

1)Open Visual Studio , Select “New Project”

2)From the templates , choose “ClassLibrary” and give a name to it. (say “Calculatordll”)

3)It creates a namespace named “Claculatordll” and a class by default. Now write the set of code which you want make as DLL. We can have more than one class here.

4)For now I will create two classes. One with calculator functionalities ( such as add , sub , mul etc) and the other class with display function.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace CalculatorDll
{
    public class CalculatorFuncions
    {
        public int add(int a, int b)
        {
            return (a + b);
        }
        public int sub(int a, int b)
        {
            return (a - b);
        }
        public int multiply(int a, int b)
        {
            return (a * b);
        }
    }
    public class DisplayFunctions
    {
        public string Display(string str)
        {
            return str;
        }
    }
}

5)Now build the project . DLL will be created in the bin folder.

Find the dll in bin folder of the project. ( bin –> Release –> CalculatorDll.dll )

Now lets see how to use this dll in another project or web application.

It can be done in 3 ways.

1)Right click on the solution and select “add reference” . the following window appears . Browse for the calculator dll created just now and click ok.

Sample code which uses the calculatordll

Aspx Code :

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="UseDLL._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 runat="server">
    <title>USING DLL</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <table>
        <tr>
            <td>
                Enter a:
            </td>
            <td>
                <asp:TextBox ID="txta" runat="server"></asp:TextBox>
            </td>
        </tr>
        <tr>
            <td>
                Enter b:
            </td>
            <td>
                <asp:TextBox ID="txtb" runat="server"></asp:TextBox>
            </td>
        </tr>
        <tr>
            <td colspan="2" align="center">
                <asp:Button ID="btnAdd" runat="server" Text="Add" OnClick="btnAdd_Click" />
                <asp:Button ID="btnSub" runat="server" Text="Subtract" OnClick="btnSub_Click" />
                <asp:Button ID="btnMul" runat="server" Text="Multiply" OnClick="btnMul_Click" />
            </td>
        </tr>
        <tr>
            <td>
                Result :
            </td>
            <td>
                <asp:TextBox ID="txtResult" runat="server"></asp:TextBox>
            </td>
        </tr>
        </table>
    </div>
    </form>
</body>
</html>

Code Behind :

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

namespace UseDLL
{
    public partial class _Default : System.Web.UI.Page
    {
        /*CREATE AN OBJECT FOR THE CLASS IN DLL AND INVOKE FUNCTIONS IN THAT CLASS*/
        CalculatorDll.CalculatorFuncions Calc = new CalculatorDll.CalculatorFuncions();
        protected void Page_Load(object sender, EventArgs e)
        {

}

        protected void btnAdd_Click(object sender, EventArgs e)
        {
            txtResult.Text = Convert.ToString(Calc.add(Int32.Parse(txta.Text), Int32.Parse(txtb.Text)));
        }

        protected void btnSub_Click(object sender, EventArgs e)
        {
            txtResult.Text = Convert.ToString(Calc.sub(Int32.Parse(txta.Text), Int32.Parse(txtb.Text)));
        }

        protected void btnMul_Click(object sender, EventArgs e)
        {
            txtResult.Text = Convert.ToString(Calc.multiply(Int32.Parse(txta.Text), Int32.Parse(txtb.Text)));
        }
    }
}

Output :

2)Add this namespace to Web.config file in your application .

In System.web tag , go to pages tag and the write the following code in “controls” tag to access this dll in your application.

<system.web>
    <pages>
            <controls>
              <add namespace="CalculatorDll" assembly ="CalculatorDll" tagPrefix="CalculatorDll"/>
            </controls>
        </pages>
</system.web>

Now to access this namespace , add “using ClaculatorDll;” to your code behind code.

3) If you want to use it in a single page , then we can register this namespace using @register directive.

Technical Blog

Monday, February 25, 2013

How to create DLL in asp.net(C#)

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