vb.net 以另一种形式访问类的同一个实例
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Accessing the same instance of a class in another form
提问by Brady
I'm sure this is a simple question, but I don't have enough experience to know the answer. :)
我确定这是一个简单的问题，但我没有足够的经验来知道答案。:)
DataClass, Form1, Form2
I have a public class, DataClass, in a separate file, DataClass.vb. In DataClassI have data stored in several arrays that I need to access. I have methods in DataClassso that I can access the data. One of them is GetName. Everything works fine on Form1. I need to access the same data in the arrays on a another form, but I am required to call a new instance of the class, so when I call the methods to access the arrays, the data is empty.
我DataClass在一个单独的文件中有一个公共类DataClass.vb. 在DataClass我有数据存储在我需要访问的几个数组中。我有方法DataClass可以访问数据。其中之一是GetName。一切正常Form1。我需要在另一个表单上访问数组中的相同数据，但是我需要调用类的新实例，因此当我调用方法访问数组时，数据为空。
I've seen some threads mention creating a singleton class, but most are about C# which I am not as familiar with.
我已经看到一些线程提到创建一个singleton class，但大多数是关于 C# 的，我不太熟悉。
What is the best practice?
最佳做法是什么？
回答by xfx
There are many ways in which you can do this.
One of them would involve creating a Moduleand then making the variable that instantiates your class Publicinside the module:
有很多方法可以做到这一点。其中之一将涉及创建一个Module，然后创建Public在模块内实例化您的类的变量：
Module MyGlobalVariables
Public MyDataClass As DataClass
End Module
Now, all the forms in your project will be able to access the DataClassvia MyGlobalVariables.MyDataClass.
现在，您项目中的所有表单都可以访问DataClassvia MyGlobalVariables.MyDataClass.
A preferable method would be to add a property to your Form2 that can be set to the DataClassinstance:
一个更好的方法是向您的 Form2 添加一个可以设置为DataClass实例的属性：
Public Property MyDataClass As DataClass
Then, you would instantiate your Form2as follows (assuming the variable you use to instantiate DataClassin Form1is called _dataClass):
然后，你会实例化Form2如下（假设你使用实例化的变量DataClass在Form1被调用_dataClass）：
Dim frm2 As New Form2()
frm2.MyDataClass = _dataClass
frm2.Show()
And finally, another way would be to override the constructor of Form2and allow it to receive a parameter of type DataClass. Then, you could instantiate Form2as:
最后，另一种方法是覆盖 的构造函数Form2并允许它接收类型为 的参数DataClass。然后，您可以实例Form2化为：
Dim frm2 As New Form2(_dataClass)
Hope this helps...
希望这可以帮助...
回答by Olivier Jacot-Descombes
You can create a singleton class like this
你可以像这样创建一个单例类
Public Class DataClass
Public Shared ReadOnly Instance As New DataClass()
Private Sub New()
End Sub
' Other members here
End Class
You can access a single instance through the shared Instancemember which is initialized automatically. The constructor Newis private in order to forbid creating a new instance from outside of the class.
您可以通过Instance自动初始化的共享成员访问单个实例。构造函数New是私有的，以禁止从类外部创建新实例。
You can access the singleton like this
您可以像这样访问单身人士
Dim data = DataClass.Instance
But this is not possible
但这是不可能的
Dim data = new DataClass() 'NOT POSSIBLE!
Since the singleton class is accessed through the class name, you can access it from the two forms easily.
由于单例类是通过类名访问的，因此可以很容易地从两种形式访问它。
