public class k1
{
public int this[int index]
{
get { throw new NotImplementedException(); }
set { throw new NotImplementedException(); }
}

}
public class k2
{
public int this[int index]
{
get { throw new NotImplementedException(); }
set { throw new NotImplementedException(); }
}

}

public class c
{
public k1 x1;
public k2 x2;
}