using System;

public class Program

{

    public static void Main()

    {

        var input = new A1();

        var result = input switch

        {

            A2 _ => RunMethod1(input),

            A3 _ => RunMethod2(input),

            A1 _ => RunMethod3(input)    

        };

    }

    static int RunMethod1(A1 a1)=>1;

    static int RunMethod2(A1 a1)=>1;

    static int RunMethod3(A1 a1)=>1;

}

​

​

​

public class A1

{

    public string Id1 {get;set;}

}

​

public class A2 : A1

{

    public string Id2 {get;set;}

}

​

public class A3 : A1

{

    public string Id3 {get;set;}

}