WPF錯誤：找不到目標元素的管理FrameworkElement我有一個帶有圖像的Row的數(shù)據(jù)網(wǎng)格。此圖像與某個狀態(tài)的觸發(fā)器綁定。當(dāng)狀態(tài)改變時我想改變圖像。模板本身在DataGridTemplateColumn的HeaderStyle上設(shè)置。此模板具有一些綁定。第一個綁定日顯示它是什么日期，狀態(tài)通過觸發(fā)器更改圖像。這些屬性在ViewModel中設(shè)置。屬性：public class HeaderItem{     public string Day { get; set; }     public ValidationStatus State { get; set; }}this.HeaderItems = new ObservableCollection<HeaderItem>();         for (int i = 1; i < 15; i++)         {             this.HeaderItems.Add(new HeaderItem()             {                 Day = i.ToString(),                 State = ValidationStatus.Nieuw,             });         }數(shù)據(jù)網(wǎng)格：<DataGrid x:Name="PersoneelsPrestatiesDataGrid" HorizontalAlignment="Stretch" VerticalAlignment="Stretch"               AutoGenerateColumns="False" SelectionMode="Single" ItemsSource="{Binding CaregiverPerformances}" FrozenColumnCount="1" >     <DataGridTemplateColumn HeaderStyle="{StaticResource headerCenterAlignment}" Header="{Binding HeaderItems[1]}" Width="50">                 <DataGridTemplateColumn.CellEditingTemplate>                     <DataTemplate>                         <TextBox Text="{ Binding Performances[1].Duration,Converter={StaticResource timeSpanConverter},Mode=TwoWay}"/>                     </DataTemplate>                 </DataGridTemplateColumn.CellEditingTemplate>                 <DataGridTemplateColumn.CellTemplate>                     <DataTemplate>                         <TextBlock TextAlignment="Center" Text="{ Binding Performances[1].Duration,Converter={StaticResource timeSpanConverter}}"/>                     </DataTemplate>                 </DataGridTemplateColumn.CellTemplate>             </DataGridTemplateColumn> </DataGrid>現(xiàn)在，當(dāng)我啟動項目時，圖像沒有顯示，我收到此錯誤：System.Windows.Data錯誤：2：找不到目標元素的管理FrameworkElement或FrameworkContentElement。BindingExpression：路徑= HeaderItems [0]; 的DataItem = NULL; target元素是'DataGridTemplateColumn'（HashCode = 26950454）; target屬性是'Header'（類型'Object'）為什么會出現(xiàn)此錯誤