If we use Sealed classes in the program, then we can't inherit it.

In C#, the sealed modifier is used to define a class as sealed.

Below are two examples where we can use sealed key word for the class :

1st example

Below program will run successfully even after using the sealed keyword.

using System;sealed class Restclass
{
    public int
Add(int x, int y)
    {
        return x +
y;
    }
}
class program
{
    static void
Main(string[] args)
    {
        Restclass
implecls = new Restclass();
        int total =
implecls.Add(4, 5);
       
Console.WriteLine("Total = {0} " ,total);
       
Console.ReadLine();
    }
}

2nd example :

Below program will not run as Test class is sealed which cannot be inherit. 

Public sealed class Test
{
public int Number;
public string Name;
} 
Public sealed class child1:Test
{
public string Name;
}