如何从WindowsFormsHost获取子控件属性？WPF空引用异常求助

动态创建的WindowsFormsHost仅设置.Name属性不会自动加入WPF元素的名称范围（Name Scope），导致FindName方法无法找到目标控件，返回Nothing，进而触发空引用异常。

解决方式 #

1. 注册名称到元素的名称范围 #

在将WinHost添加到Grid前，调用RegisterName把它注册到EmailSend_Grid的名称范围中：

Dim WinHost As New WindowsFormsHost
With WinHost
    .Name = "WinHost"
    .Child = HTMLEditor
End With
Grid.SetRow(WinHost, 5)
EmailSend_Grid.RegisterName(WinHost.Name, WinHost) ' 新增注册名称的代码
EmailSend_Grid.Children.Add(WinHost)

2. 直接保留控件引用 #

在类级别声明变量存储控件实例，后续直接访问即可，避免查找失败：

' 类级别声明变量
Private WinHost As WindowsFormsHost
Private HTMLEditor As HTMLEditControl

' 创建控件的代码
HTMLEditor = New HTMLEditControl
With HTMLEditor
    .Name = "EmailSend_Editor"
    .EnableInlineSpelling = True
End With

WinHost = New WindowsFormsHost
With WinHost
    .Name = "WinHost"
    .Child = HTMLEditor
End With
Grid.SetRow(WinHost, 5)
EmailSend_Grid.Children.Add(WinHost)

' 后续直接访问变量
Dim targetEditor = HTMLEditor

3. 遍历子元素查找控件 #

如果无法保留引用，可通过遍历Grid的子元素定位目标：

Dim WinHost As WindowsFormsHost = EmailSend_Grid.Children.OfType(Of WindowsFormsHost)().FirstOrDefault(Function(w) w.Name = "WinHost")
If WinHost IsNot Nothing Then
    Dim HTMLEditor As HTMLEditControl = CType(WinHost.Child, HTMLEditControl)
    ' 执行后续操作
End If

内容的提问来源于stack exchange，提问作者gchq