MyClass2 = MyClass1 - > ????为ByRef [英] MyClass2 = MyClass1 -> ByRef????
问题描述
我有2个用户定义类的实例。当我执行cls2 = cls1，并且我更改了cls2的属性时，我的cls1中的属性也发生了变化!!
有谁知道是什么这是为什么？以及如何阻止它？
谢谢，
彼得
我是使用VB.NET 2003.
这是我的示例代码：
Private Sub Button1_Click（ByVal sender As System.Object，ByVal e As
System.EventArgs）处理Button1.Click
Dim cls1 As new clsMyClass
Dim cls2 as clsMyClass
cls2 = Nothing
cls2 = cls1
MessageBox.Show（cls1.Icon什么都没有）
Dim bmp As New Bitmap（20,20，Imaging.PixelFormat.Format32bppPArgb ）
cls2.Icon = bmp
MessageBox.Show（cls1.Icon什么都没有）
End Sub
公共类clsMyClass
私有m_Icon作为位图
公共属性图标（）作为位图
获取
返回m_Icon
结束获取
设置（ByVal值为位图）
m_Icon =价值
结束集
结束财产
结束班
有很多方法可以做到这一点，但是防止它的一种方法
将使用这样的复制构造函数： （这应该可以做到这一点）
公共类clsMyClass
私有m_Icon作为位图
Public Sub New（ ）
''暂时不做任何事，但你可以添加你的代码
End Sub
Public Sub New（ ByVal ClsToCopy as clsMyClass）
Me.Icon = ClsToCopy.Icon
End Sub
Public Property Icon（）As Bitmap
获取
返回m_Icon
结束获取
设置（ByVal值为位图）
m_Icon =价值
结束套件
结束物业
结束班级
" DraguVaso" < PI ********** @ hotmail.com> écritdansle message de
news：呃************* @ TK2MSFTNGP10.phx.gbl ...
我有2个用户定义类的实例。当我执行cls2 = cls1，并且我更改了cls2的属性时，我的cls1中的属性也发生了变化!!
有谁知道这是什么原因？以及如何防止它？
谢谢，
Pieter
我正在使用VB.NET 2003.
这是我的示例代码：
Private Sub Button1_Click（ByVal sender As System.Object，ByVal e As
System.EventArgs）处理Button1.Click
Dim cls1 As New clsMyClass
Dim cls2 as clsMyClass
cls2 = Nothing
cls2 = cls1
MessageBox.Show（cls1.Icon什么都没有）
Dim bmp As New Bitmap（20,20） ，
Imaging.PixelFormat.Format32bppPArgb）cls2.Icon = bmp
MessageBox.Show（cls1.Icon什么都没有）
End Sub
Public Class clsMyClass
私有m_Icon作为位图
公共属性图标（）作为位图
获取
返回m_Icon
结束获取
设置（ByVal值为位图）
m_Icon =价值
结束集
结束属性
结束类
那是因为cls1和cls2是对象的*引用*而不是
实际对象本身。将cls2分配给cls1简单地使它们
都引用相同的对象，这就是为什么更改属性
会影响两者。
我建议您在用户定义的
类中实现ICloneable接口，并执行类似
cls2 =（MyClass）cls1.Clone（）;
问候
Senthil
DraguVaso写道：我有用户定义的类的2个实例。当我执行cls2 = cls1，
并更改cls2的属性时，此属性也在我的
cls1中更改!!
你没有两个实例，你只有一个。
你的实例是在这一行创建的：
\\ \
Dim cls1 As new clsMyClass
///
以下行不会创建另一个实例，它只是指向在cls1已经引用的现有实例中，cls2
：
\\\
cls2 = cls1
///
此后，cls1和cls2都指向同一个对象实例，因此你所描述的行为就是
。
为了防止它，创建两个对象实例：
\\\
Dim cls1 As新clsMyClass
Dim cls2 As new clsMyClass
///
-
（O）enone
Hi,
I have 2 instances of a user-defined class. When I do a cls2 = cls1, and I
change a property of cls2, this property is also changed in my cls1!!
Does anybody know what the reason of this is? and how I can prevent it?
Thanks,
Pieter
I''m using VB.NET 2003.
This is my sample code:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click
Dim cls1 As New clsMyClass
Dim cls2 As clsMyClass
cls2 = Nothing
cls2 = cls1
MessageBox.Show(cls1.Icon Is Nothing)
Dim bmp As New Bitmap(20, 20, Imaging.PixelFormat.Format32bppPArgb)
cls2.Icon = bmp
MessageBox.Show(cls1.Icon Is Nothing)
End Sub
Public Class clsMyClass
Private m_Icon As Bitmap
Public Property Icon() As Bitmap
Get
Return m_Icon
End Get
Set(ByVal Value As Bitmap)
m_Icon = Value
End Set
End Property
End Class解决方案Hi,
There are probably many ways to accomplish this, but one way to prevent it
would be to use a copy constructor like this: (That should do the trick)
Public Class clsMyClass
Private m_Icon As Bitmap
Public Sub New()
''Do nothing for now, but you can add your code to it
End Sub
Public Sub New(ByVal ClsToCopy as clsMyClass)
Me.Icon = ClsToCopy.Icon
End Sub
Public Property Icon() As Bitmap
Get
Return m_Icon
End Get
Set(ByVal Value As Bitmap)
m_Icon = Value
End Set
End Property
End Class
"DraguVaso" <pi**********@hotmail.com> a écrit dans le message de
news:uh*************@TK2MSFTNGP10.phx.gbl...Hi,
I have 2 instances of a user-defined class. When I do a cls2 = cls1, and I
change a property of cls2, this property is also changed in my cls1!!
Does anybody know what the reason of this is? and how I can prevent it?
Thanks,
Pieter
I''m using VB.NET 2003.
This is my sample code:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click
Dim cls1 As New clsMyClass
Dim cls2 As clsMyClass
cls2 = Nothing
cls2 = cls1
MessageBox.Show(cls1.Icon Is Nothing)
Dim bmp As New Bitmap(20, 20, Imaging.PixelFormat.Format32bppPArgb) cls2.Icon = bmp
MessageBox.Show(cls1.Icon Is Nothing)
End Sub
Public Class clsMyClass
Private m_Icon As Bitmap
Public Property Icon() As Bitmap
Get
Return m_Icon
End Get
Set(ByVal Value As Bitmap)
m_Icon = Value
End Set
End Property
End Class
That''s because cls1 and cls2 are *references* to objects and not the
actual objects themselves. Assigning cls2 to cls1 simply makes them
both refer to the same object and that''s why changing a property
affects both.
I suggest you implement the ICloneable interface in your user defined
class and do something like
cls2 = (MyClass)cls1.Clone();
Regards
Senthil
DraguVaso wrote:I have 2 instances of a user-defined class. When I do a cls2 = cls1,
and I change a property of cls2, this property is also changed in my
cls1!!
You don''t have two instances, you only have one.
Your instance is created in this line:
\\\
Dim cls1 As New clsMyClass
///
The following line does not create another instance, it simply points cls2
at the existing instance that cls1 is already referencing:
\\\
cls2 = cls1
///
After this, both cls1 and cls2 are pointing to the same object instance,
hence the behaviour you described.
To prevent it, create two object instances:
\\\
Dim cls1 As New clsMyClass
Dim cls2 As New clsMyClass
///
--
(O)enone
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