您的代码不起作用，因为 ViewBag 是一个 动态对象 不是真实"类型.

Your code doesnt work because ViewBag is a dynamic object not a 'real' type.

以下代码应该可以工作:

the following code should work:

public static bool Has (this object obj, string propertyName) 
{
    var dynamic = obj as DynamicObject;
    if(dynamic == null) return false;
    return dynamic.GetDynamicMemberNames().Contains(propertyName);
}