//获得类所在的程序集名称（此处我选择当前程序集）
string bllName = System.IO.Path.GetFileNameWithoutExtension(System.Reflection.Assembly.GetExecutingAssembly().Location);

//获得类名（我此处是提前写入Button的Name属性）
string className = (sender as Button).Name;

//获得类全名，格式：WpfApplication.ToggleButton
string fullClassName = bllName + "." + className; 

//根据类名称创建类实例
var bllObject = System.Reflection.Assembly.Load(bllName).CreateInstance(fullClassName);