"ParameterExpression of type 'B' cannot be used for delegate parameter of type 'System.Object'"

I have some classes and need to call a function on all "String" type (recursively). For example:

        public class A : ILo
        {
            public string Prop1 { get; set; }
            public Guid Id { get; set; }
            public B BInfo { get; set; }
            public List<C> ListOfC { get; set; }
        }

        public class B : ILo
        {
            public string Prop2 { get; set; }
            public Guid Id { get; set; }
            public D DInfo { get; set; }
            public List<E> ListOfE { get; set; }
        }
        public class C : ILo
        {
            public string Prop3 { get; set; }
            public Guid Id { get; set; }
        }
        public class D : ILo
        {
            public string Prop4 { get; set; }
            public Guid Id { get; set; }
        }
        public class E : ILo
        {
            public string Prop5 { get; set; }
            public Guid Id { get; set; }
        }

--------------
    public T DoSomthing<T>(T need) where T: class
    {
        if (need == null) return default(T);
        var t = need.GetType();
        var props = t.GetProperties();
        foreach (var propInfo in props)
        {
            if (propInfo.PropertyType == typeof(string))
            {
                ParameterExpression pe = Expression.Parameter(t);
                Expression propExp = Expression.Property(pe, propInfo);
                Expression<Func<T, string>> eFunc = Expression.Lambda<Func<T, string>>(propExp, pe);
                var locVal = MyCustomMethod1(need, eFunc, ((ILo)need).GetId());

                propInfo.SetValue(need, locVal);
            }
            else if (propInfo.PropertyType.IsClass)
            {
                var temp = Convert.ChangeType(propInfo.GetValue(need), propInfo.PropertyType);
                DoSomthing(temp);
            }
            else if (propInfo.PropertyType.IsArray)
            {
                // do DoSomthing for all items
            }
        }
        return need;
    }

I have a method that named 'DoSomething' and when I call it, I gets Error. My error is: "ParameterExpression of type 'B' cannot be used for delegate parameter of type 'System.Object'". Someone please help me.