If we had added a getValue method to class Leaf, we would either have to return some sort of flag value indicating that the method application is non-sensical or actually throw an exception.

如果我们已经向 Leaf 类添加了 getValue 方法，我们要么是不得不返回一些类型的标志值表明此方法应用是无意义的，要么是实际抛出一个异常。

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Finally, I use GetProperty to get information about a specified property of the control and then get the value of the control property using the GetValue method.

最后使用GetProperty获取控件的指定属性的信息，并使用GetValue方法获取控件属性值。

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