我的ListPicker组件有问题。我从http://code.msdn.microsoft.com/Windows-Phone-71-Local-da2fdf80下载了一个示例。它是编译，但是当我想更改页面（包含ListPicker）时，抛出了异常。
System.Windows.Markup.XamlParseException occurred
Message=Set property 'Microsoft.Phone.Controls.ListPicker.ItemCountThreshold' threw an exception. [Line: 42 Position: 63]
LineNumber=42
LinePosition=63
StackTrace:
at System.Windows.Application.LoadComponent(Object component, Uri resourceLocator)
at PhoneApp.Views.TaskEditView.InitializeComponent()
at PhoneApp.Views.TaskEditView..ctor()
at System.Reflection.RuntimeConstructorInfo.InternalInvoke(RuntimeConstructorInfo rtci, BindingFlags invokeAttr, Binder binder, Object parameters, CultureInfo culture, Boolean isBinderDefault, Assembly caller, Boolean verifyAccess, StackCrawlMark& stackMark)
at System.Reflection.RuntimeConstructorInfo.InternalInvoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, StackCrawlMark& stackMark)
at System.Activator.InternalCreateInstance(Type type, Boolean nonPublic, StackCrawlMark& stackMark)
at System.Activator.CreateInstance(Type type)
at System.Windows.Navigation.PageResourceContentLoader.BeginLoad_OnUIThread(AsyncCallback userCallback, PageResourceContentLoaderAsyncResult result)
at System.Windows.Navigation.PageResourceContentLoader.<>c__DisplayClass4.<BeginLoad>b__0(Object args)
at System.Reflection.RuntimeMethodInfo.InternalInvoke(RuntimeMethodInfo rtmi, Object obj, BindingFlags invokeAttr, Binder binder, Object parameters, CultureInfo culture, Boolean isBinderDefault, Assembly caller, Boolean verifyAccess, StackCrawlMark& stackMark)
at System.Reflection.RuntimeMethodInfo.InternalInvoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, StackCrawlMark& stackMark)
at System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters)
at System.Delegate.DynamicInvokeOne(Object[] args)
at System.MulticastDelegate.DynamicInvokeImpl(Object[] args)
at System.Delegate.DynamicInvoke(Object[] args)
at System.Windows.Threading.DispatcherOperation.Invoke()
at System.Windows.Threading.Dispatcher.Dispatch(DispatcherPriority priority)
at System.Windows.Threading.Dispatcher.OnInvoke(Object context)
at System.Windows.Hosting.CallbackCookie.Invoke(Object[] args)
at System.Windows.Hosting.DelegateWrapper.InternalInvoke(Object[] args)
at System.Windows.RuntimeHost.ManagedHost.InvokeDelegate(IntPtr pHandle, Int32 nParamCount, ScriptParam[] pParams, ScriptParam& pResult)
InnerException: System.NotSupportedException
Message=Cannot set read-only property 'Microsoft.Phone.Controls.ListPicker.ItemCountThreshold'.
StackTrace:
at MS.Internal.XamlMemberInfo.SetValue(Object target, Object value)
at MS.Internal.XamlManagedRuntimeRPInvokes.SetValue(XamlTypeToken inType, XamlQualifiedObject& inObj, XamlPropertyToken inProperty, XamlQualifiedObject& inValue)
at MS.Internal.XcpImports.Application_LoadComponentNative(IntPtr pContext, IntPtr pComponent, UInt32 cUriStringLength, String uriString, UInt32 cXamlStrLength, Byte* pXamlStr, UInt32 cAssemblyStrLength, String assemblyStr)
at MS.Internal.XcpImports.Application_LoadComponent(IManagedPeerBase componentAsDO, String resourceLocator, UnmanagedMemoryStream stream, UInt32 numBytesToRead, String assemblyString)
at System.Windows.Application.LoadComponent(Object component, Uri resourceLocator)
at PhoneApp.Views.TaskEditView.InitializeComponent()
at PhoneApp.Views.TaskEditView..ctor()
at System.Reflection.RuntimeConstructorInfo.InternalInvoke(RuntimeConstructorInfo rtci, BindingFlags invokeAttr, Binder binder, Object parameters, CultureInfo culture, Boolean isBinderDefault, Assembly caller, Boolean verifyAccess, StackCrawlMark& stackMark)
at System.Reflection.RuntimeConstructorInfo.InternalInvoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, StackCrawlMark& stackMark)
at System.Activator.InternalCreateInstance(Type type, Boolean nonPublic, StackCrawlMark& stackMark)
at System.Activator.CreateInstance(Type type)
at System.Windows.Navigation.PageResourceContentLoader.BeginLoad_OnUIThread(AsyncCallback userCallback, PageResourceContentLoaderAsyncResult result)
at System.Windows.Navigation.PageResourceContentLoader.<>c__DisplayClass4.<BeginLoad>b__0(Object args)
at System.Reflection.RuntimeMethodInfo.InternalInvoke(RuntimeMethodInfo rtmi, Object obj, BindingFlags invokeAttr, Binder binder, Object parameters, CultureInfo culture, Boolean isBinderDefault, Assembly caller, Boolean verifyAccess, StackCrawlMark& stackMark)
at System.Reflection.RuntimeMethodInfo.InternalInvoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, StackCrawlMark& stackMark)
at System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters)
at System.Delegate.DynamicInvokeOne(Object[] args)
at System.MulticastDelegate.DynamicInvokeImpl(Object[] args)
at System.Delegate.DynamicInvoke(Object[] args)
at System.Windows.Threading.DispatcherOperation.Invoke()
at System.Windows.Threading.Dispatcher.Dispatch(DispatcherPriority priority)
at System.Windows.Threading.Dispatcher.OnInvoke(Object context)
at System.Windows.Hosting.CallbackCookie.Invoke(Object[] args)
at System.Windows.Hosting.DelegateWrapper.InternalInvoke(Object[] args)
at System.Windows.RuntimeHost.ManagedHost.InvokeDelegate(IntPtr pHandle, Int32 nParamCount, ScriptParam[] pParams, ScriptParam& pResult)
这是我的XAML页面：
<local:EntityEditPage
x:Class="PhoneApp.Views.TaskEditView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"
xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone"
xmlns:toolkit="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone.Controls.Toolkit"
xmlns:local="clr-namespace:PhoneApp.Views"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
FontFamily="{StaticResource PhoneFontFamilyNormal}"
FontSize="{StaticResource PhoneFontSizeNormal}"
Foreground="{StaticResource PhoneForegroundBrush}"
SupportedOrientations="Portrait" Orientation="Portrait"
mc:Ignorable="d" d:DesignHeight="696" d:DesignWidth="480"
shell:SystemTray.IsVisible="True">
<!--LayoutRoot is the root grid where all page content is placed-->
<Grid x:Name="LayoutRoot" Background="Transparent">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<!--TitlePanel contains the name of the application and page title-->
<StackPanel x:Name="TitlePanel" Grid.Row="0" Margin="12,17,0,28">
<TextBlock x:Name="ApplicationTitle" Text="MY APPLICATION" Style="{StaticResource PhoneTextNormalStyle}"/>
<TextBlock x:Name="PageTitle" Text="edit task" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/>
</StackPanel>
<!--ContentPanel - place additional content here-->
<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
<ScrollViewer>
<StackPanel>
<!-- title -->
<TextBlock Text="Title" Style="{StaticResource DefaultLabelStyle}" />
<TextBox Text="{Binding Path=Title, Mode=TwoWay}" TextWrapping="Wrap" Style="{StaticResource FormTextBox}" />
<!-- project -->
<TextBlock Text="Project" Style="{StaticResource DefaultLabelStyle}"/>
<toolkit:ListPicker x:Name="listProjects" Style="{StaticResource FormListPicker}">
<toolkit:ListPicker.FullModeItemTemplate>
<DataTemplate>
<Grid Background="Transparent" Margin="12">
<TextBlock Text="{Binding Name}" TextWrapping="Wrap" Style="{StaticResource PhoneTextLargeStyle}" />
</Grid>
</DataTemplate>
</toolkit:ListPicker.FullModeItemTemplate>
<toolkit:ListPicker.ItemTemplate>
<DataTemplate>
<Grid>
<TextBlock Text="{Binding Name}" TextWrapping="Wrap" />
</Grid>
</DataTemplate>
</toolkit:ListPicker.ItemTemplate>
</toolkit:ListPicker>
<!-- date -->
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<StackPanel>
<TextBlock VerticalAlignment="Center" Text="Date" Style="{StaticResource DefaultLabelStyle}" />
<toolkit:DatePicker x:Name="datePicker" Style="{StaticResource FormDatePicker}" />
</StackPanel>
<StackPanel Grid.Column="1">
<TextBlock VerticalAlignment="Center" Text="Time" Style="{StaticResource DefaultLabelStyle}" />
<toolkit:TimePicker x:Name="timePicker" />
</StackPanel>
</Grid>
<!-- status -->
<TextBlock Text="Status" Style="{StaticResource DefaultLabelStyle}"/>
<toolkit:ListPicker x:Name="listStatus" ListPickerMode="Normal" SelectedItem="{Binding Status, Mode=TwoWay}">
<toolkit:ListPicker.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding}"/>
</DataTemplate>
</toolkit:ListPicker.ItemTemplate>
</toolkit:ListPicker>
<!-- description -->
<TextBlock Text="Description" Style="{StaticResource DefaultLabelStyle}" />
<TextBox Text="{Binding Path=Description, Mode=TwoWay}" Height="285" TextWrapping="Wrap" AcceptsReturn="True" Style="{StaticResource FormTextBox}" />
</StackPanel>
</ScrollViewer>
</Grid>
</Grid>
<!--Sample code showing usage of ApplicationBar-->
<phone:PhoneApplicationPage.ApplicationBar>
<shell:ApplicationBar>
<shell:ApplicationBarIconButton IconUri="/icons/appbar.check.rest.png" Text="button" Click="OnOK"/>
<shell:ApplicationBarIconButton IconUri="/icons/appbar.cancel.rest.png" Text="button" Click="OnCancel"/>
</shell:ApplicationBar>
</phone:PhoneApplicationPage.ApplicationBar>
</local:EntityEditPage>