摆脱Visual Studio命名空间错误消息

Question

this is unfortunately a very beginner question:

I am doing the very simple WPF tutorials and I am stuck on a namespace problem. I want to do a simple hierarchical treeview binding on a custom object according to the tutorial. I put the object into a custom namespace "MyNameSpace" and declared this in XAML ( xmlns:MyTree="clr-namespace:MyNameSpace"). I believe I don't need to specify the assembly as I am just in my project without any further reference (new and clean project).

The problem I have now, is that the compiler gives me an error at

 <HierarchicalDataTemplate  DataType="{x:Type MyTree:MenuItemNew}"

with the message

The name "MenuItemNew" does not exist in the namespace "clr-namespace:MyNameSpace"

But it does exist! AND it even compiles and starts the program correctly. However, I cannot see the layout anymore because of "Invalid Markup".

So how can I tell XAML to accept my namespace? Or what would be a best way to solve this?

Here is the XAML:

<Window x:Class="TreeViewTestC.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:MyTree="clr-namespace:MyNameSpace"
        Title="MainWindow" Height="350" Width="525">
    <Grid Margin="10">
        <TreeView Name="trvMenu">
            <TreeView.ItemTemplate>
                <HierarchicalDataTemplate  DataType="{x:Type MyTree:MenuItemNew}" ItemsSource="{Binding Items}">
                    <TextBlock Text="{Binding Title}" />
                </HierarchicalDataTemplate>
            </TreeView.ItemTemplate>
        </TreeView>
    </Grid>
</Window>

and here is my MainWindow Code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.IO;
using System.Collections.ObjectModel;
using MyNameSpace;

namespace TreeViewTestC
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            MenuItemNew root = new MenuItemNew() { Title = "Menu1" };
            MenuItemNew childItem1 = new MenuItemNew() { Title = "Child item #1" };
            childItem1.Items.Add(new MenuItemNew() { Title = "Child item #1.1" });
            childItem1.Items.Add(new MenuItemNew() { Title = "Child item #1.2" });
            root.Items.Add(childItem1);
            root.Items.Add(new MenuItemNew() { Title = "Child item #2" });
            trvMenu.Items.Add(root);
        }
    }
}

namespace MyNameSpace
{
    public class MenuItemNew
    {
        public MenuItemNew()
        {
            this.Items = new ObservableCollection<MenuItemNew>();
        }

        public string Title { get; set; }

        public ObservableCollection<MenuItemNew> Items { get; set; }
    }
}

Answer 1

It seems to me that your main application namespace is TreeViewTestC and not MyNameSpace . Therefore, you may well need to tell the compiler that your MyNameSpace is actually in the TreeViewTestC assembly, despite you only having a single project. Try using this instead:

xmlns:MyTree="clr-namespace:MyNameSpace;assembly=TreeViewTestC"

Answer 2

Ok, I found the solution. The project was on a network drive. Moving it to a local folder solves the issues... Man, what a mess. This has cost me so much time and I need the network drive..

More info: The name "XYZ" does not exist in the namespace "clr-namespace:ABC"

Thanks a lot for your help