Name does not exist in the namespace

问题:

I am working on a simple UWP project using data template binding in VS 2015. When ever I try to specify the type for the Datatemplate I get an error.

XAML:

<Page x:Name="RootPage"
x:Class="Adaptive_News_Layout.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
xmlns:local="using:Adaptive_News_Layout"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d" FontSize="22" >

 <SplitView x:Name="MySplitView" Grid.Row="1" DisplayMode="CompactOverlay" Background="LightGray" OpenPaneLength="200"  >
            <SplitView.Pane>
                <ListView x:Name="MyListview" ItemsSource="{x:Bind NavigationItems}"  >
                    <ListView.ItemTemplate>
                        <DataTemplate x:DataType="local:NavItem" >
                            <StackPanel Orientation="Horizontal">
                                <RelativePanel>
                                    <Button x:Name="Icon"  FontFamily="Segoe MDL2 Assets" Content="{x:Bind ButtonIcon}" Width="50" Height="50"/>
                                    <TextBlock x:Name="Section" Text="{x:Bind SectionTitle}" RelativePanel.RightOf="Icon" />
                                </RelativePanel>
                            </StackPanel>
                        </DataTemplate>
                    </ListView.ItemTemplate>

This is the class:

namespace Adaptive_News_Layout
{
    public class NavItem
    {
        public string ButtonIcon { get; set; }
        public string SectionTitle { get; set; }
    }
}

The error reads: The name "NavItem" does not exist in the namespace "using:Adaptive_News_Layout"

回答1:

I figured out what the problem was. It's a glitch in Visual Studio 2015. After you add a namespace in XAML it's best to compile/ test run your program or you will get this problem. To fix it just:

1. Delete the namespace reference in question and all usages of that reference.
2. Perform a test run/ compile your program.
3. Add the namespace reference back into the opening page tag
4. Perform another test run/ compile your program.

Now when you use your new namespace reference the compiler won't glitch out.

回答2:

I found that I had unintentionally defined the same object in a sub-namespace. once I got rid of the second definition, this problem disappeared

回答3:

You have to declare 'local' namespace in section which can be found on the top of ypur Xaml file. You will see many namespace with format xmlns:Name ="value" Add your name space with Name =local and Value as your Namespace