新手錯誤：WPF應用程序中發生XamlParseException

Question

我嘗試使用以下示例構建WPF應用程序：Windows示例WPF應用程序 。 但是，在處理過程中出現以下錯誤

“在'System.Windows.StaticResourceExtension'上提供值”引發了異常。 行號“ 36”和行位置“ 55”。

並拋出以下行

 <ListBox Name="peopleListBox" Grid.Column="1" Grid.Row="2" 
         ItemsSource="{Binding Source={StaticResource ExpenseDataSource}, XPath=Person}"
         ItemTemplate="{StaticResource nameItemTemplate}">
        </ListBox>

內部異常提供以下詳細信息

{“找不到名為'nameItemTemplate'的資源。資源名稱區分大小寫。”}

這是有問題的xaml。

<Page x:Class="ExpenseIt.ExpenseItHome"
      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
      xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
      xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
      mc:Ignorable="d" 
      d:DesignHeight="300" d:DesignWidth="300"
    Title="ExpenseIt-Home">

    <Grid Margin="10,0,10,10">
        <Grid.Background>
            <ImageBrush ImageSource="2012-12-20 13.27.57.jpg"  />
        </Grid.Background>

        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="230" />
            <ColumnDefinition />
        </Grid.ColumnDefinitions>

        <Grid.RowDefinitions>
            <RowDefinition/>
            <RowDefinition Height="Auto"/>
            <RowDefinition />
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>

        <!-- People list -->

        <Label Grid.Column="1" Style="{StaticResource headerTextStyle}" >
            View Expense Report
        </Label>

        <Border Grid.Column="1" Grid.Row="1" Style="{StaticResource listHeaderStyle}">
            <Label Style="{StaticResource listHeaderTextStyle}">Names</Label>
        </Border>
        <ListBox Name="peopleListBox" Grid.Column="1" Grid.Row="2" 
         ItemsSource="{Binding Source={StaticResource ExpenseDataSource}, XPath=Person}"
         ItemTemplate="{StaticResource nameItemTemplate}">
        </ListBox>



        <!-- View report button -->
        <Button Grid.Column="1" Grid.Row="3" Click="Button_Click" Style="{StaticResource buttonStyle}">View</Button>
        <Grid.Resources>

            <!-- Expense Report Data -->
            <XmlDataProvider x:Key="ExpenseDataSource" XPath="Expenses">
                <x:XData>
                    <Expenses xmlns="">
                        <Person Name="Mike" Department="Legal">
                            <Expense ExpenseType="Lunch" ExpenseAmount="50" />
                            <Expense ExpenseType="Transportation" ExpenseAmount="50" />
                        </Person>
                        <Person Name="Lisa" Department="Marketing">
                            <Expense ExpenseType="Document printing"
      ExpenseAmount="50"/>
                            <Expense ExpenseType="Gift" ExpenseAmount="125" />
                        </Person>
                        <Person Name="John" Department="Engineering">
                            <Expense ExpenseType="Magazine subscription" 
     ExpenseAmount="50"/>
                            <Expense ExpenseType="New machine" ExpenseAmount="600" />
                            <Expense ExpenseType="Software" ExpenseAmount="500" />
                        </Person>
                        <Person Name="Mary" Department="Finance">
                            <Expense ExpenseType="Dinner" ExpenseAmount="100" />
                        </Person>
                    </Expenses>
                </x:XData>
            </XmlDataProvider>


            <!-- Name item template -->
            <DataTemplate x:Key="nameItemTemplate">
                <Label Content="{Binding XPath=@Name}"/>// isnt this enough?
            </DataTemplate> 
        </Grid.Resources>
    </Grid>
</Page>

我對我做錯了什么以及如何糾正它有任何幫助，將不勝感激！ 謝謝！

Answer 1

此錯誤表明未找到StaticResource密鑰。 使用靜態資源時，必須在引用之前在App.Xaml或當前文件中定義它們。

因此，請確保示例中的“ ExpenseDataSource”和“ nameItemTemplate”包含在頂級Grid.Resources下：

<Page ...>
    <Grid ...>
        <Grid.Resources>
            <!-- Name item template -->
            <DataTemplate x:Key="nameItemTemplate">
                <Label Content="{Binding XPath=@Name}"/>
            </DataTemplate>

            <!-- Expense Report Data -->
            <XmlDataProvider x:Key="ExpenseDataSource" XPath="Expenses"> 
                ...

        </Grid.Resources>

        <ListBox Name="peopleListBox" 
            ItemsSource="{Binding Source={StaticResource ExpenseDataSource}, XPath=Person}"
            ItemTemplate="{StaticResource nameItemTemplate}">

Answer 2

我遇到了具有相同示例代碼的相同問題-上面“在頂層網格下方”答案中的術語使我感到困惑，因為示例中的數據提供程序位於頂層網格內，如下所示：

<Page>
  <Grid>
    <!-- other markup that uses the Resources -->

    <Grid.Resources>
      <!-- resources stuff as above -->
    </Grid.Resources>
  </Grid>
</Page>

真正的問題是由XAML代碼的自上而下的解析引起的……顯然是單遍解析器，而不是兩次遍歷解析器（用於其他標記）。 知道這一點的解決方案是移動網格靜態資源（數據提供程序），以使其在標記中實際位於其上方。 重新標記該標記，使其更像以下內容，它將起作用……這是一個難題：

<Page>
  <Grid>
    <Grid.Resources>
      <!-- resources stuff as above -->
      <!-- Grid.Resources MUST occur ABOVE the other markup that uses resources -->
    </Grid.Resources>

    <!-- other markup that uses the Resources -->
  </Grid>
</Page>

請享用！