.net XamlReader.Load找不到静态资源

使用DataTemplateSelector在运行时创建列。在XamlReader.Load:System.Windows.StaticResourceExtension处存在异常。如何加载资源

var column = new DataGridTemplateColumn();
            column.Header = (i.Hour + 1).ToString();
            column.Width = 30;
var parserContext = new ParserContext();
parserContext.XmlnsDictionary.Add("", "http://schemas.microsoft.com/winfx/2006/xaml/presentation");
parserContext.XmlnsDictionary.Add("x", "http://schemas.microsoft.com/winfx/2006/xaml");
parserContext.XmlnsDictionary.Add("local", "clr-namespace:ССПИ;assembly=ССПИ");
column.CellTemplateSelector = (DataTemplateSelector)XamlReader.Load(
                new MemoryStream(Encoding.Default.GetBytes(
                    @"<local:ExtendedTemplateSelector TextBlockTemplate='{StaticResource TextBlockTemplate}' CheckBoxTemplate='{StaticResource CheckBoxTemplate}'/>"
                )),parserContext);        
dataGrid1.Columns.Add(column);

<DataGrid DataGridCell.Selected="DataGrid_GotFocus" EnableColumnVirtualization="true" EnableRowVirtualization="true" Name="dataGrid1" DockPanel.Dock="Top" AutoGenerateColumns="False" 
                   Height="120" Width="Auto" CanUserReorderColumns="False" CanUserResizeColumns="False" CanUserAddRows="false" CanUserResizeRows="False" CanUserSortColumns="False" CellEditEnding="dataGrid1_CellEditEnding" ContextMenuOpening="dataGrid1_ContextMenuOpening">
                    <DataGrid.Resources>
                        <DataTemplate x:Key="TextBlockTemplate">
                            <TextBlock/>
                        </DataTemplate>
                        <DataTemplate x:Key="CheckBoxTemplate">
                            <CheckBox IsChecked="False"/>
                        </DataTemplate>
                    </DataGrid.Resources>

在App.xaml中：

<App.Resources>
    <local:ExtendedTemplateSelector x:Key="MyExtendedTemplateSelector" TextBlockTemplate='{StaticResource TextBlockTemplate}' CheckBoxTemplate='{StaticResource CheckBoxTemplate}'/>
</App.Resources>

在我看来，这里不需要解析器：它只会使事情变得复杂和缓慢。所以，只要把你的资源放在你的应用程序资源或资源字典中，并这样称呼它

column.CellTemplateSelector = (DataTemplateSelector)((App)Application.Current)).Resources["MyExtendedTemplateSelector"];