将 DataGrid 当前项放入对象 WPF

Question

几天以来，我在将 WPF DataGrid 的当前项目转换为 linq-generated 实体时遇到了问题。如果有人能帮我解决这个问题，那就太棒了。 我正在使用 linq 查询获取 DataGrid 的数据，如下所示：

Dim payableexpense As New exprev
Dim listofexpenses As IEnumerable(Of exprev)

Private Sub txtsearchname_TextChanged(sender As Object, e As TextChangedEventArgs) Handles txtsearchname.TextChanged
   listofexpenses = From expenses In db.exprevs
   Where expenses.school_id = currentschool.school_id AndAlso expenses.title.Contains(txtsearchname.Text.ToString) AndAlso expenses.status <> 1 AndAlso expenses.type = 1

   dgvsearchresults.ItemsSource = listofexpenses
   dgvsearchresults.Items.Refresh()
   stpexpensedetails.DataContext = payableexpense
End Sub

对于 DataGrid 选择更改事件，我有以下代码：

Private Sub dgvsearchresults_SelectionChanged(sender As Object, e As SelectionChangedEventArgs) Handles dgvsearchresults.SelectionChanged
payableexpense = dgvsearchresults.CurrentItem
End Sub

但是在run-time 期间，它抛出了一个异常：

“无法将'ms.internal.namedobject'类型的对象转换为'exprev'”

在我项目的另一个地方，同样的方法运行良好。

Answer 1

使用TryCast 方法尝试将SelectedItem 属性转换为exprev：

Private Sub dgvsearchresults_SelectionChanged(sender As Object, e As SelectionChangedEventArgs) Handles dgvsearchresults.SelectionChanged
    Dim selectedItem As exprev = TryCast(dgvsearchresults.SelectedItem, exprev)
    If selectedItem IsNot Nothing Then
        payableexpense = selectedItem
        '...
    End If
End Sub