Well, nothing much to say, this article is taken from http://leon.mvps.org/DotNet/RegasmInstaller.html. Thanks Leon, just for my own bookmarking here are step. [Article is taken as it is from Leon’s article.]

Realising that I couldn’t be the only person who’s having this problem, I’ve decided to share the code to assist others. All you need to do is follow the below steps:

• In your main project (the one containing the class you want to register), right click the project file and select Add / New Item and select Installer Class. Call it something like clsRegisterDll.cs
• In the designer that appears, click ‘Click here to switch to code view’ or right click the clsRegisterDll.cs file in solution explorer and select View Code
• Replace the code in the window with the code listed below, and make sure you change ‘YourNamespace’. This has to match with the namespace in the clsRegisterDll.Designer.cs file.
• Compile your project
• In your installer, make sure you have added your dll to the Application Folder, and then right-click the installer project and select View / Custom Actions
• Right-click Install, and then click Add Custom Action
• Double click on Application Folder, and then on your dll
• Do the same for the Commit action
• Build and test your installer
• You should now have an installer that registers your dll using regasm /codebase.

clsRegisterDll.cs:

using System.ComponentModel;
using System.Configuration.Install;

namespace YourNamespace
{
[RunInstaller(true)]
public partial class RegisterDll : Installer
{
public RegisterDll()
{
InitializeComponent();
}

[System.Security.Permissions.SecurityPermission(System.Security.Permissions.SecurityAction.Demand)]
public override void Commit(System.Collections.IDictionary savedState)
{
base.Commit(savedState);

// Get the location of regasm
string regasmPath = System.Runtime.InteropServices.RuntimeEnvironment.GetRuntimeDirectory() + @"regasm.exe";
// Get the location of our DLL
string componentPath = typeof(RegisterDll).Assembly.Location;
// Execute regasm
System.Diagnostics.Process.Start(regasmPath, "/codebase \"" + componentPath + "\"");
}

[System.Security.Permissions.SecurityPermission(System.Security.Permissions.SecurityAction.Demand)]
public override void Install(System.Collections.IDictionary stateSaver)
{
base.Install(stateSaver);
}
}
}