包含表单的用户控件控件 [英] user control controling containing form

问题描述

我正在使用 vb.net winforms 创建一个包含用户控件的应用程序，我也在创作用户控件.

I am using vb.net winforms to create an application which contains a user control, I am also authoring the user control.

用户控件名为 activate1

The user control is named activate1

包含用户控件(和其他内容)的表单名为 form1

The form containing the usercontrol (and other content) is named form1

目前我正在尝试在 activate1 上的掩码文本框完成时启用 form1 上的按钮

currently I am trying to enable a button on form1 when a maskedtextbox on activate1 is completed

我试图通过以下方式做到这一点:

I attempted to do this by:

Private Sub MaskedTextBox1_TextChanged(sender As Object, e As EventArgs) Handles MaskedTextBox1.TextChanged
    If MaskedTextBox1.Text.Count = 34 Then
        Form1.SimpleButton1.Enabled = True
    Else
        Form1.SimpleButton1.Enabled = False
    End If
End Sub

但是我在运行应用程序时收到一个错误表单在从默认实例构建期间引用了自己，这导致了无限递归"所以我尝试了

however I receive an error when running the application "The form referred to itself during construction from a default instance, which led to infinite recursion" so instead I tried

Private Sub MaskedTextBox1_TextChanged(sender As Object, e As EventArgs) Handles MaskedTextBox1.TextChanged
    If MaskedTextBox1.Text.Count = 34 Then
        me.SimpleButton1.Enabled = True
    Else
        me.SimpleButton1.Enabled = False
    End If
End Sub

但是这个标志并且不允许编译，因为我指的是用户控件中不存在的按钮

however this flags and does not allow compiling as I am referring to a button that does not exist in the user control

我怎样才能做到这一点

推荐答案

第一个错误的原因是您使用类型名称来引用 Form1，其中您需要父表单的具体实例.您可以通过访问 ParentForm-属性:

The reason for the 1st error is that you use the type name to refer to Form1 where you'd need the concrete instance of the parent form. You can access the parent form by accessing the ParentForm-property:

Private Sub MaskedTextBox1_TextChanged(sender As Object, e As EventArgs) Handles MaskedTextBox1.TextChanged
    Dim form = TryCast(ParentForm, Form1)
    If form IsNot Nothing Then
        If MaskedTextBox1.Text.Count = 34 Then
            form.SimpleButton1.Enabled = True
        Else
            form.SimpleButton1.Enabled = False
        End If
    End If
End Sub

请注意，这种方法将您的 Form 和您的 UserControl 紧密结合在一起.虽然它可以工作，但它降低了 UserControl 的可重用性(实际上，您只能在 Form1 上使用它，而不能在其他表单上使用它).虽然你可以改进这一点，例如通过创建界面，但 UserControl 将始终以一种或另一种方式与支持此按钮的表单相关联.
一种更可重用的方法是在您的 UserControl 中引发一个事件并在父表单中处理它，例如:

Please note that this approach couples your Form and your UserControl tightly. Though it will work, it reduces the reusability of your UserControl (in fact, you can only use it on Form1 and not on other forms). Though you can improve this, e.g. by creating an interface, but the UserControl will always by tied to the forms that support this button in one way or the other.
A more reusable approach would be to raise an event in your UserControl and handle this in the parent form, e.g.:

Public Class ActivationInfoEventArgs
    Inherits EventArgs

    Public Property Completed As Boolean
End Class

Public Event ActivationInfoChanged As EventHandler(Of ActivationInfoEventArgs)

Private Sub MaskedTextBox1_TextChanged(sender As Object, e As EventArgs) Handles MaskedTextBox1.TextChanged
    Dim completed As Boolean
    If MaskedTextBox1.Text.Count = 34 Then
        completed = True
    Else
        completed = False
    End If
    RaiseEvent ActivationInfoChanged(Me, New ActivationInfoEventArgs() With { .Completed = completed })
End Sub

您为 Form1 中的事件添加一个处理程序并(取消)激活此处理程序中的按钮.这样，您就可以在更广泛的表单上使用 UserControl.

You add a handler for the event in Form1 and (de-) activate the button in this handler. This way, you can use the UserControl on a wider variety of Forms.

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