Creating C# Class Library (DLL) Using Visual Studio .NET

First of all, Creating C# Class Library in Visual Studio .NET is an easy way. Here I have described, How to create DLL in Visual Studio and How to access this DLL in our project. Here I used Visual Studio 2010.

Steps for Creating DLL

Step 1:- File->New->Project->Visual C# Projects->Class Library. Select your project name and appropriate directory click OK

Creating C# Class Library (DLL) Using Visual Studio .NET

After Clicking on button ‘OK’, solution explorer adds one C# class ‘Class1.cs’. In this class, we can write our code.

Creating C# Class Library (DLL) Using Visual Studio .NET

When we double click on Class1.cs, we see a namespace CreatingDLL. We will be using this namespace in our project to access this class library.

Creating C# Class Library (DLL) Using Visual Studio .NET

Step 2:- Within Class1.cs we create a method named ‘sum’ that takes two integers value and returns the sum to which method passed numbers.

using System;
namespace CreatingDLL
{
    public class Class1
    {
        /// <summary>
        /// sum is method that take two integer value and return that sum
        /// </summary>
        /// <param name="x"></param>
        /// <param name="y"></param>
        /// <returns></returns>
        public int sum(int x, int y)
        {
            return x + y;
        }
    }
}

Step 3:- Now build the Application and see the bin\debug directory of our project. ‘CreatingDLL.dll’ is created. Now we create another application and take this DLL (CreatingDLL.dll) reference for accessing DLL’s method.

Steps for Accessing Created DLL

Step 4:- File->New->Project->Visual C# Projects->Windows Form Application.

Step 5:- Designed windows form as a bellow figure.

Creating C# Class Library (DLL) Using Visual Studio .NET

Step 6:- Add reference of DLL (CreatingDLL) which we created before few minutes.

Creating C# Class Library (DLL) Using Visual Studio .NET

After adding reference of DLL, following windows will appear.

Creating C# Class Library (DLL) Using Visual Studio .NET

Step 7:- Write code on button click of Windows Form Application. Before creating an object and making the method of Add DLL, add namespace CreatedDLL in the project as bellow code.

using System;
using System.Windows.Forms;
using CreatingDLL;
namespace AccessingDLL
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
 
        private void btnAdd_Click(object sender, EventArgs e)
        {
            Class1 c1 = new Class1();
            try
            {
                txtResult.Text
= Convert.ToString(c1.sum(Convert.ToInt32(txtNumber1.Text), Convert.ToInt32(txtNumber2.Text)));
            }
            catch(Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
    }
}