求助：无法从共享方法引用类实例成员（XPO属性配置场景）

Hey there, let's break down what's going on here and fix that error!

First, the root cause of your "Cannot refer to an instance member of a class from a shared method" error: Attributes (like your ImageEditor attribute) are processed at compile time, which means their parameters can only be compile-time constants, static/shared members, or enum values. You can't directly reference an instance property like LogoWidth in an attribute parameter—since instance properties only exist when an object is created at runtime, the compiler can't resolve that value during compilation. If you tried to hack around this by referencing LogoWidth in a shared context, that's exactly what triggers the error you're seeing.

Now, here's the practical solution: use an XAF View Controller to dynamically set the Logo editor's width at runtime, based on the current object's LogoWidth value. This works because controllers run after your object instance is created, so you can access the LogoWidth property directly.

Solution 1: WinForms View Controller #

Create a controller that targets your business class's DetailView, then update the PictureEdit's width whenever the current object changes or the LogoWidth property is modified:

Imports DevExpress.ExpressApp
Imports DevExpress.ExpressApp.Win.Editors
Imports DevExpress.XtraEditors.Controls
Imports System.ComponentModel

Public Class LogoWidthWinController
    Inherits ViewController(Of DetailView)

    Public Sub New()
        ' Replace "YourBusinessClass" with the actual name of your entity class
        TargetObjectType = GetType(YourBusinessClass)
    End Sub

    Protected Overrides Sub OnActivated()
        MyBase.OnActivated()
        ' Subscribe to object changes
        AddHandler View.CurrentObjectChanged, AddressOf OnCurrentObjectChanged
        If View.CurrentObject IsNot Nothing Then
            AddHandler CType(View.CurrentObject, INotifyPropertyChanged).PropertyChanged, AddressOf OnObjectPropertyChanged
        End If
        ' Set initial width
        UpdateLogoEditorWidth()
    End Sub

    Protected Overrides Sub OnDeactivated()
        ' Unsubscribe to avoid memory leaks
        RemoveHandler View.CurrentObjectChanged, AddressOf OnCurrentObjectChanged
        If View.CurrentObject IsNot Nothing Then
            RemoveHandler CType(View.CurrentObject, INotifyPropertyChanged).PropertyChanged, AddressOf OnObjectPropertyChanged
        End If
        MyBase.OnDeactivated()
    End Sub

    Private Sub OnCurrentObjectChanged(sender As Object, e As EventArgs)
        ' Re-subscribe to the new object's PropertyChanged event
        If View.CurrentObject IsNot Nothing Then
            AddHandler CType(View.CurrentObject, INotifyPropertyChanged).PropertyChanged, AddressOf OnObjectPropertyChanged
        End If
        UpdateLogoEditorWidth()
    End Sub

    Private Sub OnObjectPropertyChanged(sender As Object, e As PropertyChangedEventArgs)
        ' Update width only when LogoWidth changes
        If e.PropertyName = NameOf(YourBusinessClass.LogoWidth) Then
            UpdateLogoEditorWidth()
        End If
    End Sub

    Private Sub UpdateLogoEditorWidth()
        Dim logoEditor = View.FindItem("Logo") As ImagePropertyEditor
        If logoEditor IsNot Nothing AndAlso logoEditor.Control IsNot Nothing Then
            Dim pictureEdit = logoEditor.Control As DevExpress.XtraEditors.PictureEdit
            ' Set the width from the current object's LogoWidth property
            pictureEdit.Width = CType(View.CurrentObject, YourBusinessClass).LogoWidth
            ' Optional: Set size mode to stretch/fit the image to the new width
            pictureEdit.Properties.SizeMode = PictureSizeMode.Stretch
        End If
    End Sub
End Class

Solution 2: Blazor View Controller #

If you're working with XAF Blazor, the approach is similar but targets Blazor-specific editors:

Imports DevExpress.ExpressApp
Imports DevExpress.ExpressApp.Blazor.Editors
Imports System.ComponentModel

Public Class LogoWidthBlazorController
    Inherits ViewController(Of DetailView)

    Public Sub New()
        TargetObjectType = GetType(YourBusinessClass)
    End Sub

    Protected Overrides Sub OnActivated()
        MyBase.OnActivated()
        AddHandler View.CurrentObjectChanged, AddressOf OnCurrentObjectChanged
        If View.CurrentObject IsNot Nothing Then
            AddHandler CType(View.CurrentObject, INotifyPropertyChanged).PropertyChanged, AddressOf OnObjectPropertyChanged
        End If
        UpdateLogoEditorWidth()
    End Sub

    Protected Overrides Sub OnDeactivated()
        RemoveHandler View.CurrentObjectChanged, AddressOf OnCurrentObjectChanged
        If View.CurrentObject IsNot Nothing Then
            RemoveHandler CType(View.CurrentObject, INotifyPropertyChanged).PropertyChanged, AddressOf OnObjectPropertyChanged
        End If
        MyBase.OnDeactivated()
    End Sub

    Private Sub OnCurrentObjectChanged(sender As Object, e As EventArgs)
        If View.CurrentObject IsNot Nothing Then
            AddHandler CType(View.CurrentObject, INotifyPropertyChanged).PropertyChanged, AddressOf OnObjectPropertyChanged
        End If
        UpdateLogoEditorWidth()
    End Sub

    Private Sub OnObjectPropertyChanged(sender As Object, e As PropertyChangedEventArgs)
        If e.PropertyName = NameOf(YourBusinessClass.LogoWidth) Then
            UpdateLogoEditorWidth()
        End If
    End Sub

    Private Sub UpdateLogoEditorWidth()
        Dim logoEditor = View.FindItem("Logo") As DxImagePropertyEditor
        If logoEditor IsNot Nothing Then
            ' Set width using CSS units (px, %, etc.)
            logoEditor.ComponentModel.Width = $"{CType(View.CurrentObject, YourBusinessClass).LogoWidth}px"
        End If
    End Sub
End Class

Key Notes: #

• Replace YourBusinessClass with the actual name of your entity class (the one containing Logo and LogoWidth properties).
• The ImmediatePostData attribute on LogoWidth ensures that changes to the width are sent to the server immediately, which triggers our PropertyChanged handler to update the editor right away.
• This approach avoids the compile-time restriction of attributes, since we're modifying the editor at runtime when the object instance is available.

内容的提问来源于stack exchange，提问作者Luk