Question

Form1在点击Form2弹出窗口时有一个“ADD”按钮。 Form2有两个按钮“OK”和“CANCEL”。
Form2有一些数据可供选择，用户可以选择数据并按“OK”或点击“取消”。
如果不选择数据并按OK或单击取消按钮，用户可能不会离开表单。我想强制用户点击“确定”或“取消”按钮。只有这样用户才能离开Form2。

请帮助我在vb.net中实现这一目标。

Answer 1

一个基本的想法是检查文本框选择长度是否等于文本框中文本框的文本长度，然后有一个布尔变量，如果没有设置阻止表单关闭，就像这样。

Public Class MyDialog
    Dim closeValid As Boolean
    Private Sub ExitButton_Click(sender As Object, e As EventArgs) Handles btnOk.Click
        If TextBox1.SelectionLength = TextBox1.Text.Length Then
            closeValid = True
            Close()
        End If
    End Sub

    Private Sub btnCancel_Click(sender As Object, e As EventArgs) Handles btnCancel.Click
        closeValid = True
        Close()
    End Sub

    Private Sub MyDialog_FormClosing(sender As Object, e As FormClosingEventArgs) Handles MyBase.FormClosing
        If Not closeValid Then e.Cancel = True
    End Sub

End Class

实际上，更好的方法是拦截Dialogs FormClosing事件中的结束原因并根据UserClosing关闭原因对其进行测试，这样如果应用程序关闭或系统关闭您的应用程序将不会挂起。然后，您可以向DialogResult提供适当的CloseReason，并在您的表单从ShowDialog调用返回时进行测试。

<强> Form1中

Public Class Form1
    Private Sub Button_Click(sender As Object, e As EventArgs) Handles btnOk.Click
        Dim form2 As New MyDialog
        Dim dr As DialogResult = form2.ShowDialog()
        If dr = Windows.Forms.DialogResult.OK Then
            'Process your OK
        ElseIf dr = Windows.Forms.DialogResult.Cancel Then
            'Process your Cancel
        Else
            'Do Something
        End If
    End Sub
End Class

<强>窗体2

Public Class MyDialog
    Private Sub MyDialog_FormClosing(sender As Object, e As FormClosingEventArgs) Handles MyBase.FormClosing
        If e.CloseReason = CloseReason.UserClosing Then e.Cancel = True 'This is true if user clicks the X
    End Sub

    Private Sub btnExit_Click(sender As Object, e As EventArgs) Handles btnExit.Click
        DialogResult = Windows.Forms.DialogResult.Cancel
    End Sub

    Private Sub btnOk_Click(sender As Object, e As EventArgs) Handles btnOk.Click
        If TextBox1.SelectionLength = TextBox1.Text.Length Then
            DialogResult = Windows.Forms.DialogResult.OK
        End If
    End Sub
End Class

Answer 2

您应该使用ShowDialog打开第二个表单。在第二个表单上，单击按钮上的DialogResult。像这样：

Dim frm2 = new Form2()
If frm2.ShowDialog()==DialogResult.OK Then
'do something because the user clicked OK

End If

Answer 3

1）创建一个Global函数（最好在模块中，这样你只需要声明一次）

Imports System.Runtime.InteropServices                 ' required imports
Public intInputBoxCancel as integer                    ' public variable

Public Function StrPtr(ByVal obj As Object) As Integer
    Dim Handle As GCHandle = GCHandle.Alloc(obj, GCHandleType.Pinned)
    StrPtr = Handle.AddrOfPinnedObject.ToInt32
    Handle.Free()
End Function

在表单load事件中放入此（使变量intInputBoxCancel = cancel事件）

intInputBoxCancel = StrPtr(String.Empty)

现在，您可以在表单中的任何位置使用（如果StrPtr在模块中声明为全局，则可以使用项目）

dim ans as string = inputbox("prompt")         ' default data up to you
if StrPtr(ans) = intInputBoxCancel then
   ' cancel was clicked
else
   ' ok was clicked (blank input box will still be shown here)
endif

强制用户在VB.NET中选择数据

3 个答案: