vb.net 结构中的属性：“表达式是一个值，因此不能成为赋值的目标。”
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Properties in Structures: "Expression is a value and therefore cannot be the target of an assignment."
提问by serhio
I have the following 2 structures, and I don't really understand why the second one does not work:
我有以下两个结构，我真的不明白为什么第二个不起作用：
Module Module1
Sub Main()
Dim myHuman As HumanStruct
myHuman.Left.Length = 70
myHuman.Right.Length = 70
Dim myHuman1 As HumanStruct1
myHuman1.Left.Length = 70
myHuman1.Right.Length = 70
End Sub
Structure HandStruct
Dim Length As Integer
End Structure
Structure HumanStruct
Dim Left As HandStruct
Dim Right As HandStruct
End Structure
Structure HumanStruct1
Dim Left As HandStruct
Private _Right As HandStruct
Public Property Right As HandStruct
Get
Return _Right
End Get
Set(value As HandStruct)
_Right = value
End Set
End Property
End Structure
End Module
More detailed explanation:I have some obsolete code that uses structures instead of classes. So I need to identify a moment when a filed of this structure changes to the wrong value.
更详细的解释：我有一些使用结构而不是类的过时代码。因此，我需要确定此结构的字段更改为错误值的时刻。
My solution to debug was to replace the structure filed by a property with the same name, and then I just set a breackpoint in the property setter to identify the moment when I receive the wrong value... in order do not rewrite all the code.... just for debugging purpose.
我的调试解决方案是用同名的属性替换结构体，然后在属性设置器中设置一个断点来识别我收到错误值的时刻......为了不重写所有代码.... 仅用于调试目的。
Now, I faced the problem above, so I don't know what to do... only setting the breakpoint everywhere this member of structure is assigned, but there is a lot of lines with that assignment...
现在，我遇到了上面的问题，所以我不知道该怎么办......只在分配这个结构成员的任何地方设置断点，但是有很多行与该分配......
回答by Kevin DiTraglia
It's just a matter of what is happening when you run the program. The getter returns a copy of your struct, you set a value on it, then that copy of the struct goes out of scope (so the modified value doesn't do anything). The compiler shows this as an error since it is probably not what you intended. Do something like this:
这只是运行程序时发生了什么的问题。getter 返回您的结构的副本，您在其上设置一个值，然后该结构的副本超出范围（因此修改后的值不会执行任何操作）。编译器将此显示为错误，因为它可能不是您想要的。做这样的事情：
Dim tempRightHand as HandStruct
tempRightHand = myHuman.Right
tempRightHand.Length = 70
myHuman.Right = tempRightHand
The left works because you are accessing it directly instead of through a property.
左边是有效的，因为您是直接访问它而不是通过属性访问它。
