只读PropertyGrid

Question

我需要在PropertyGrid中显示一个满足以下要求的对象:该对象及其子对象必须是只读的，能够激活PropertyGrid的CollectionEditors。

我找到了一个与我需要的非常匹配的样本，但有一种意想不到的行为我搞不懂。对于不同的对象，我有多个PropertyGrids。在SetBrowsablePropertiesAsReadOnly中，我循环了一个对象，但令人惊讶的是，我的项目中的所有PropertyGrids都是只读的。有人能帮我吗。代码如下：

Imports System.Reflection
Imports System.ComponentModel

Public Class PropertyGridEx
    Inherits PropertyGrid

    Private isReadOnly As Boolean
    Public Property [ReadOnly]() As Boolean
        Get
            Return Me.isReadOnly
        End Get
        Set(ByVal value As Boolean)
            Me.isReadOnly = value
            Me.SetBrowsablePropertiesAsReadOnly(Me.SelectedObject, value)
        End Set
    End Property

    Protected Overloads Sub OnSelectedObjectsChanged(ByVal e As EventArgs)
        Me.SetBrowsablePropertiesAsReadOnly(Me.SelectedObject, Me.isReadOnly)
        MyBase.OnSelectedObjectsChanged(e)
    End Sub

    Private Sub SetBrowsablePropertiesAsReadOnly(ByRef selectedObject As Object, ByVal isReadOnly As Boolean)
        If selectedObject IsNot Nothing Then
            Dim props As PropertyDescriptorCollection = TypeDescriptor.GetProperties(selectedObject)
            For Each propDescript As PropertyDescriptor In props
                If propDescript.IsBrowsable AndAlso propDescript.PropertyType.GetInterface("ICollection", True) Is Nothing Then
                    Dim attr As ReadOnlyAttribute = TryCast(propDescript.Attributes(GetType(ReadOnlyAttribute)), ReadOnlyAttribute)
                    If attr IsNot Nothing Then
                        Dim field As FieldInfo = attr.[GetType]().GetField("isReadOnly", BindingFlags.NonPublic Or BindingFlags.Instance)
                        field.SetValue(attr, isReadOnly, BindingFlags.NonPublic Or BindingFlags.Instance, Nothing, Nothing)
                    End If
                End If
            Next
        End If
    End Sub
End Class

Answer 1

ReadOnly属性在类定义上设置，而不是在对象的实例上设置。因此，这将对该类的所有实例产生影响。

要实现所需的功能，请创建一个在其中覆盖IsReadOnly属性的自定义PropertyDescriptor，并将其应用于对象实例的属性。

Answer 2

我确信这不是正确的vb语法，但这可以通过添加一个属性来完成：

Private Sub SetBrowsablePropertiesAsReadOnly(ByRef selectedObject As Object, ByVal isReadOnly As Boolean)
  If selectedObject IsNot Nothing Then
    TypeDescriptor.AddAttributes(selectedObject, New Attribute[] { New ReadOnlyAttribute(isReadOnly) });
  End If
End Sub