Where can I put custom classes in ASP.NET MVC?

I have some utility functions and Pagination function. I want to create classes named Utility and Pagination for these functions respectively, so that I can use these class function in more than one controllers.

So where can I put these class in my folder structure, and how can I access then?

You can either create a new Folder called Helpers under the root and keep your classes physically there. I would keep my classes under a different namespace called Helpers

namespace MyProject.Helpers
{
  public class CustomerHelper
  {
        //Do your class stuff here
  }
}

To accees this in my other classes (Ex : Controllers) ,I can either use the fully qualified name

var custHelper=new MyProject.Helpers.CustomerHelper(); 

OR

add a Import statement at the top so that i can skip the fully qualified name

//Other existing Import statements here
using MyProject.Helpers;
public class RackController : Controller
{
  public ActionResult Index()
  {
     var custHelper=new CustomerHelper(); 
     //do something with this  
     return View();    
  } 
}

If you think your Helper method can be used in another project also, You may consider to keep them physically in a separate project(of type class library). To use this in your project, Add a reference to this project and use it like what we did above (use either fully qualified name or use import statement)

You can put your helper classes anywhere you find logical and convenient.

Personally I create a folder Helpers off of the main project folder.

You can use them anywhere, either by fully qualifying the class name or with a using statement.

In a Razor view, you would use

@using MyProject.Helpers

In a controller or model you would use

using MyProject.Helpers;

Another approach could be creating a Base Controller class and adding your common logic there, and deriving your controller from your base controller.

public class MyBaseController:Controller
{
   public void CommonFunction()
    {
    }
}

Use like...

public HomeController:MyBaseController
{
}

You can create a new project,and then put the common classes into the project . If you want to use them,just Add Reference the project.

Also, Please be sure to set the "Build Action" of your Class to "Compile". In Visual Studio 2015, By default, every Class created within the App_Code (by right click -> Add -> Class) got "Content" as Build Action.