我一直收到这个错误:
System.NullReferenceException was unhandled by user code
Message=[Arg_NullReferenceException]
Arguments:
Debugging resource strings are unavailable. Often the key and arguments provide sufficient information to diagnose the problem. See http://go.microsoft.com/fwlink/?linkid=106663&Version=5.0.60401.00&File=mscorlib.dll&Key=Arg_NullReferenceException
StackTrace:
at Jantire.DoHomeworkView.TextAlignment_combobox_SelectionChanged(Object sender, SelectionChangedEventArgs e)
at System.Windows.Controls.Primitives.Selector.OnSelectionChanged(SelectionChangedEventArgs e)
at System.Windows.Controls.Primitives.Selector.InvokeSelectionChanged(List`1 unselectedItems, List`1 selectedItems)
at System.Windows.Controls.Primitives.Selector.SelectionChanger.End()
at System.Windows.Controls.Primitives.Selector.OnItemsChanged(NotifyCollectionChangedEventArgs e)
at System.Windows.Controls.ItemsControl.OnItemCollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)
at System.Collections.Specialized.NotifyCollectionChangedEventHandler.Invoke(Object sender, NotifyCollectionChangedEventArgs e)
at System.Windows.Controls.ItemCollection.NotifyCollectionChanged(NotifyCollectionChangedEventArgs e)
at System.Windows.Controls.ItemCollection.NotifyCollectionReady()
at System.Windows.Controls.ItemsControl.NotifyAllItemsAdded(IntPtr nativeItemsControl)
InnerException:
在代码中:
private void TextAlignment_combobox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
//This next line is where error is at
if (TextAlignment_combobox.SelectedIndex == 0)
{
EssayContents_richtextbox.Selection.ApplyPropertyValue(Paragraph.TextAlignmentProperty, TextAlignment.Left);
}
if (TextAlignment_combobox.SelectedIndex == 1)
{
EssayContents_richtextbox.Selection.ApplyPropertyValue(Paragraph.TextAlignmentProperty, TextAlignment.Center);
}
if (TextAlignment_combobox.SelectedIndex == 2)
{
EssayContents_richtextbox.Selection.ApplyPropertyValue(Paragraph.TextAlignmentProperty, TextAlignment.Right);
}
}
使用XAML:
<ComboBox Width="128" x:Name="TextAlignment_combobox" SelectionChanged="TextAlignment_combobox_SelectionChanged" ToolTipService.ToolTip="Text Alignment">
<ComboBoxItem Name="LeftAlignment_comboboxitem" Content="Left Alignment" IsSelected="True"/>
<ComboBoxItem Name="CenterAlignment_comboboxitem" Content="Center Alignment"/>
<ComboBoxItem Name="RightAlignment_comboboxitem" Content="Right Alignment"/>
</ComboBox>