如何为PropertyGrid绑定的类添加命令？VB示例代码求助

要在PropertyGrid底部显示针对SampleClass实例的重置命令，你需要通过类型描述扩展为类添加设计器动词（DesignerVerb），PropertyGrid会自动识别并展示这些动词作为底部操作链接。以下是具体实现步骤：

1. 实现自定义类型描述提供者 #

创建自定义的TypeDescriptionProvider和TypeDescriptor，用来为SampleClass添加重置动词：

Imports System.ComponentModel
Imports System.Windows.Forms.Design

Public Class SampleClassTypeDescriptionProvider
    Inherits TypeDescriptionProvider

    Public Sub New()
        MyBase.New(TypeDescriptor.GetProvider(GetType(SampleClass)))
    End Sub

    Public Overrides Function GetTypeDescriptor(ByVal objectType As Type, ByVal instance As Object) As ICustomTypeDescriptor
        Dim baseDescriptor = MyBase.GetTypeDescriptor(objectType, instance)
        Return New SampleClassTypeDescriptor(baseDescriptor, instance)
    End Function
End Class

Public Class SampleClassTypeDescriptor
    Inherits CustomTypeDescriptor
    Private ReadOnly _sampleInstance As SampleClass

    Public Sub New(parent As ICustomTypeDescriptor, instance As Object)
        MyBase.New(parent)
        _sampleInstance = DirectCast(instance, SampleClass)
    End Sub

    Public Overrides Function GetVerbs() As DesignerVerbCollection
        Dim verbs = MyBase.GetVerbs()
        ' 添加重置实例的动词
        verbs.Add(New DesignerVerb("重置实例", AddressOf OnResetInstance))
        Return verbs
    End Function

    Private Sub OnResetInstance(sender As Object, e As EventArgs)
        ' 调用实例的Reset方法
        _sampleInstance.Reset()
        ' 通知PropertyGrid刷新属性值
        With TypeDescriptor.GetProperties(_sampleInstance)
            .Item("Value1").ResetValue(_sampleInstance)
            .Item("Value2").ResetValue(_sampleInstance)
        End With
    End Sub
End Class

2. 为SampleClass绑定类型描述提供者 #

修改SampleClass，添加TypeDescriptionProviderAttribute指定我们的自定义提供者：

<TypeDescriptionProvider(GetType(SampleClassTypeDescriptionProvider))>
Public Class SampleClass
    Public Const DefValue = 1
    Public Property Value1 As Integer = DefValue
    Public Property Value2 As Integer = DefValue
    Public Sub Reset()
        Value1 = DefValue
        Value2 = DefValue
    End Sub
End Class

3. 验证效果 #

运行窗体后，PropertyGrid底部会出现「重置实例」的操作链接，点击后会执行SampleClass的Reset方法，同时PropertyGrid会自动刷新显示属性的默认值。

补充说明 #

• 如果需要为单个属性添加重置选项，只需给属性添加DefaultValueAttribute，右键属性即可看到重置选项；
• 若你的类继承自Component，也可以通过添加DesignerAttribute并在自定义Designer中添加DesignerVerb来实现，不过对于普通类，使用TypeDescriptionProvider是更通用的方案。

内容的提问来源于stack exchange，提问作者Bogdan Samchuk