How to create Assembly in .Net C#.

An assembly is the primary building block of a .NET Framework application.
It is an Output Unit. Assemblies contain MSIL code.
– Assembly physically exist as DLLs or EXEs
– One assembly can contain one or more files
–  The constituent files can include any file types like image files, text files etc. along with DLLs or EXEs
– When you compile your source code by default the exe/dll generated is actually an assembly.

Manifest: Assembly manifest is a data structure which stores information about an assembly
Assembly Metadata is stored in the Manifest.

Metadata: is a data about data.

There are 2 types of assemblies.
1. Private Assembly
2.Shared Assembly (Public) – C:\windows\assembly
By default, assemblies are private.

A private assembly is used only by a single application, and is stored in application folder, or in a subfolder.
When the .net code gets compiled it generates an assembly which is stored in bin folder.

Shared assemblies (also called strong named assemblies) are copied to a single location (usually the Global assembly cache)
– Shared assembly can be used by multiple application and has a strong name.
– Strong name indicate the assembly, Version number, culture identity and public key token.

Now, We learn how to create assembly in c#.

STEP 1 – First Start the Visual Studio and Create New Class Library Project.

create an assembly in c#
create an assembly in c#

STEP 2 – Now we have created Class Library, write below code in Class1.cs

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

namespace MeeraLibrary
/// <summary>
/// Summary description for Class1.
/// </summary>
public class ChangeCharacter
public string UpperCase(string text)
return text.ToUpper();
public string LowerCase(string text)
return text.ToLower();

create assembly in C#
create assembly in C#

After doing this Build an application, for generate the ClassLibrary1.dll
The ClassLibrary1.dll file automatically generated by compiling the application in Your Application/Bin/Debug Folder.

STEP 3 – Now use the assembly, create a new web application. then add ClassLibray1.dll by add reference to Bin Folder.

add assembly to web application in c#
add assembly to web application in c#

After creating a New web application  –> Right Click on Project —> Add Reference
Select Browse option to select the ClassLibrary1.dll which you created before.

Create assembly in
Create assembly in

– Now you have added ClassLibrary1.dll in Bin Folder.

create assembly in C#
create assembly in C#

Write the below code for design web form:

<form id=”form1″ runat=”server”>
<asp:Button ID=”Button1″ runat=”server” onclick=”Button1_Click” Text=”Upper” />
<asp:Button ID=”Button2″ runat=”server” onclick=”Button2_Click” Text=”Lower” />
<asp:TextBox ID=”TextBox1″ runat=”server”></asp:TextBox>

How to use class library in c#
How to use class library in c#

write below code on Button Click Event at code behind page:

protected void Button1_Click(object sender, EventArgs e)
MeeraLibrary.ChangeCharacter mm = new  MeeraLibrary.ChangeCharacter();
TextBox1.Text=    mm.UpperCase(TextBox1.Text);
protected void Button2_Click(object sender, EventArgs e)
MeeraLibrary.ChangeCharacter mm = new MeeraLibrary.ChangeCharacter();
TextBox1.Text = mm.LowerCase(TextBox1.Text);


I hope you will enjoy this tutorials about creating assembly.

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