The partial class help you separate your class to multiple files. As you know, C# provides the ability to have a single class implementation in multiple .cs files using the partial modifier keyword

For Example

Student1.cs

using System;

namespace CSharp
{
    public partial class Student
    {
        public void Add()
        {
            Console.WriteLine("Add student !");
        }

        public void Edit()
        {
            Console.WriteLine("Edit student !");
        }

        //...etc
    }
}

Student2.cs

using System;

namespace CSharp
{
    public partial class Student
    {
        public void Show()
        {
            Console.WriteLine("Display student information !");
        }
    }
}

In main class you can use the partial class as shown below

using System;

namespace CSharp
{
    class Program
    {
        static void Main(string[] args)
        {
            Student obj = new Student();
            obj.Add();
            obj.Show();
        }
    }
}

You can also apply partial modifier to a class, method, interface or structure