using System;

​

public struct TestStruct

{

    public int X;

    public int Y;

    public override string ToString(){

        return $"{this.X} {this.Y}";

    }

}

​

public class Program

{

    public static void Main()

    {

        var myStruct = new TestStruct(){X=10, Y=20};

        var anotherStruct = new TestStruct(){X=1, Y=2};

        ref var myRef = ref SomeFunc(ref myStruct);

        Console.WriteLine(myStruct);

        Console.WriteLine(myRef);

        myRef.Y = 11;

        myRef = anotherStruct;

        Console.WriteLine(myStruct);

        Console.WriteLine(myRef);

​

    }

    public static ref TestStruct SomeFunc(ref TestStruct st){

        st.X += 20;

        st.Y = 5;

        return  ref st;

    }

}