只读PropertyGrid

时间:2008-12-15 04:03:29

标签: .net reflection propertygrid propertydescriptor readonly-attribute

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

我发现了一个与我需要的样本非常匹配的样本,但是有一个我想不通的意外行为。我有不止一个PropertyGrids用于不同的对象。在SetBrowsablePropertiesAsReadOnly中,我循环一个对象,但令人惊讶的是我的项目中的所有PropertyGrids都变为只读。任何人都可以帮助我。这是代码:



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

2 个答案:

答案 0 :(得分:0)

我确定这不是正确的vb语法,但可以通过添加属性来完成:

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

答案 1 :(得分:0)

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

要实现您的目标,请创建一个自定义PropertyDescriptor,在其中覆盖IsReadOnly属性,并将其应用于对象实例的属性。