如何通过一个公共属性将两个自定义对象相互比较?

我有一个具有以下属性的电影对象

public class Movie {
    private string title;
    ...other similar properties...
}

如何实现在二叉树中使用的CompareTo()类?

我到目前为止所做的是

public int CompareTo(object obj)
{
    Movie m1 = (Movie)obj;

    return this.title.CompareTo(m1.title);
}

By trying to use the pre-existing CompareTo() function in string, but it won't work.