C# Online Compiler | .NET Fiddle

using System;
					
public class Program
{
	public static void Main()
	{
		int j = 5;

		switch (j)
		{
			case 5:
				Console.WriteLine(5);
				switch (j - 1)
				{
					case 4:
						Console.WriteLine(4);
						switch (j - 2)
						{
							case 3:
								Console.WriteLine(3);
								break;
						}
						break;
				}
				break;
			case 10:
				Console.WriteLine(10);
				break;
			case 15:
				Console.WriteLine(15);
				break;
			default:
				Console.WriteLine(100);
				break;
		}
	}
}

 
using System;
                    
public class Program
{
    public static void Main()
    {
        int j = 5;
​
        switch (j)
        {
            case 5:
                Console.WriteLine(5);
                switch (j - 1)
                {
                    case 4:
                        Console.WriteLine(4);
                        switch (j - 2)
                        {
                            case 3:
                                Console.WriteLine(3);
                                break;
                        }
                        break;
                }
                break;
            case 10:
                Console.WriteLine(10);
                break;
            case 15:
                Console.WriteLine(15);
                break;
            default:
                Console.WriteLine(100);
                break;
        }
    }
}

Compilation error (line 12, col 0): 'If' must end with a matching 'End If'.
Compilation error (line 12, col 0): ')' expected.