在Designer支持下将表单作为属性添加到用户控件 [英] Adding a Form as a property to a user control with Designer support

问题描述

我已经创建了一个自定义标签.它具有 Form 类型的属性，用户可以在设计器中选择该表单，然后单击标签时将加载该表单.它可以正常工作，但属性下拉列表中的唯一形式是标签所在的形式.

是否可以显示所有可能的表单，或者让用户将表单作为字符串传递，然后将其转换为表单?

这是我标签的代码:

 公共类BMLabel私有t作为字符串私有ID作为字符串私人frm作为新形式<类别("BM")>公共属性类型为字符串得到返回t结束获取设置(值作为字符串)t =值端套最终财产公共属性标识符为字符串得到返回编号结束获取设置(值作为字符串)id =值端套最终财产公共财产表格得到返回frm结束获取设置(值形式)frm =值端套最终财产私有Sub BMLabel_Click(作为对象发送，作为EventArgs发送)处理我.昏暗t = frm.GetType()昏暗的形式为Form = DirectCast(Activator.CreateInstance(t)，Form)form.ShowDialog()结束子末级 

解决方案

问题是，当您声明类型为 Form 的属性时，它允许您选择 form实例，而不是继承自 Form 的类型/类.您需要做的是声明一个类型为 Type 的属性，并准备编辑器，该编辑器将允许您选择所需的类型(将选项限制为从 Form ).

免责声明:创建自定义编辑器的想法是受

 公共类FormTypeSelector朋友属性值作为类型私有子FormTypeSelector_Load(发送者作为对象，e作为EventArgs)处理MyBase.Load昏暗的availableFormTypes =System.Reflection.Assembly.GetExecutingAssembly().GetTypes().其中(Function(t)t.BaseType = GetType(Form)And t Me.GetType()).ToList()cboFormTypes.DisplayMember =名称"cboFormTypes.DataSource = availableFormTypescboFormTypes.SelectedItem =值结束子Private Sub BtnOK_Click(发送者为对象，e作为EventArgs)处理btnOK.Click值= DirectCast(cboFormTypes.SelectedItem，类型)DialogResult = DialogResult.OK关闭()结束子私有Sub btnCancel_Click(发送者为对象，e作为EventArgs)处理btnCancel.ClickDialogResult = DialogResult.Cancel关闭()结束子末级 

就是这样；它应该准备好了:

注意:您可能需要在 FormTypeSelector 中添加一个选项，以允许清除 FormType 属性的选定值，这应该很容易做到.

I have created a custom label. It has a property of type Form, which the user can select the form in the designer and then when the label is clicked that form is loaded. It works fine but the only form in the properties dropdown list is the one that the label is on.

Is there a way to show all possible forms or perhaps have the user pass the form as a string and then convert that to be a form.

Here is the code for my label:

Public Class BMLabel
    Private t As String
    Private id As String
    Private frm As New Form

    <Category("BM")>
    Public Property Type As String
        Get
            Return t
        End Get
        Set(value As String)
            t = value
        End Set
    End Property

    Public Property Identifier As String
        Get
            Return id
        End Get
        Set(value As String)
            id = value
        End Set
    End Property

    Public Property Form As Form
        Get
            Return frm
        End Get
        Set(value As Form)
            frm = value
        End Set
    End Property

    Private Sub BMLabel_Click(sender As Object, e As EventArgs) Handles Me.Click
        Dim t = frm.GetType()

        Dim form As Form = DirectCast(Activator.CreateInstance(t), Form)
        form.ShowDialog()
    End Sub
End Class

解决方案

The problem is that when you declare a property of type Form, it allows you to select a form instance, not a type/class that inherits from Form. What you need to do instead is declare a property of type Type and prepare the editor which will allow you to select the desired type (limiting the options to the types that inherit from Form).

Disclaimer: The idea of creating a custom editor was inspired by this answer and the code was adapted for this particular situation.

So, here we go. The custom label class would look something like this:

Public Class BMLabel
    Inherits Label
    ' Don't forget to change the namespace.
    '        ↓↓↓↓↓↓↓↓↓↓↓
    <Editor("WindowsApp1.TypeSelector, System.Design", GetType(UITypeEditor)), Localizable(True)>
    Public Property FormType As Type

    Private Sub BMLabel_Click(sender As Object, e As EventArgs) Handles Me.Click
        Using frm As Form = DirectCast(Activator.CreateInstance(FormType), Form)
            frm.ShowDialog(Me)
        End Using
    End Sub
End Class

Now, we need to create the TypeSelector class:

Public Class TypeSelector
    Inherits UITypeEditor

    Public Overrides Function GetEditStyle(context As ITypeDescriptorContext) As UITypeEditorEditStyle
        If context Is Nothing OrElse context.Instance Is Nothing Then
            Return MyBase.GetEditStyle(context)
        End If

        Return UITypeEditorEditStyle.Modal
    End Function

    Public Overrides Function EditValue(context As ITypeDescriptorContext, provider As IServiceProvider, value As Object) As Object
        Dim editorService As IWindowsFormsEditorService

        If context Is Nothing OrElse context.Instance Is Nothing OrElse provider Is Nothing Then
            Return value
        End If

        editorService = DirectCast(provider.GetService(GetType(IWindowsFormsEditorService)),
                                   IWindowsFormsEditorService)

        Dim dlg As New FormTypeSelector()
        dlg.Value = DirectCast(value, Type)
        dlg.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen
        If editorService.ShowDialog(dlg) = System.Windows.Forms.DialogResult.OK Then
            Return dlg.Value
        End If
        Return value
    End Function
End Class

Then, we create a form called FormTypeSelector with a ComboBox or a ListBox to list the available options:

Public Class FormTypeSelector
    Friend Property Value As Type

    Private Sub FormTypeSelector_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Dim availableFormTypes =
            System.Reflection.Assembly.GetExecutingAssembly().
                    GetTypes().
                    Where(Function(t) t.BaseType = GetType(Form) AndAlso t <> Me.GetType()).ToList()
        cboFormTypes.DisplayMember = "Name"
        cboFormTypes.DataSource = availableFormTypes
        cboFormTypes.SelectedItem = Value
    End Sub

    Private Sub BtnOK_Click(sender As Object, e As EventArgs) Handles btnOK.Click
        Value = DirectCast(cboFormTypes.SelectedItem, Type)
        DialogResult = DialogResult.OK
        Close()
    End Sub

    Private Sub btnCancel_Click(sender As Object, e As EventArgs) Handles btnCancel.Click
        DialogResult = DialogResult.Cancel
        Close()
    End Sub
End Class

And that's it; it should be ready to go:

Note: You'll probably need to add an option in FormTypeSelector to allow clearing the selected value of the FormType property which should be easy enough to do.

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