来自父XAML类的TreeView在不同的项目中但在相同的命名空间中不存在于“当前上下文”中

Question

So, I created a child class based off a base XAML (see below), but I created the child class in another project and Visual Studio gives me an error on the TreeView saying "The name "ViewTree" does not exist in the current context". However, the other child classes that exist, which are located inside the same project do not have the same error. Why is this?

I've added a reference to the other project, and used the same namespace, but still no joy.

Thanks!

Base XAML:

<UserControl x:Class="myLibrary.Material.ViewTreeSpace.ViewingTree"
             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" Background="#00000000" >
    <DockPanel>
        <TreeView Name="ViewTree" />
    </DockPanel>
</UserControl>

Parent code-behind:

namespace myLibrary.Material.ViewTreeSpace {
    public partial class ViewingTree : Usercontrol {
        public string TreeName = String.Empty;
        public ViewingTree(){ }
}

Child class in different project:

namespace myLibrary.Material.ViewTreeSpace {
    public class ImportedTree : ViewingTree {
        public ImportedTree() : base() {
            ViewTree.Items.Clear(); // <- This line gives me error
            TreeName = "My imported Tree in another project."; // <- This works
        }
}

Edit: I've also noticed that variables that exist in code-behind can be referenced, only UIElements from the cannot.

Edit: Upon receiving @Liju answer, I set my TreeView to use the x:FieldModifier="public" . However, I get the below error now.

System.Exception: The component 'myLibrary.Material.ViewTreeSpace.ImportedTree' does not have a resource identified by the URI '/myLibrary;component/material/view%20tree/viewingtree.xaml'.
at System.Windows.Application.LoadComponent(Object component, Uri resourceLocator)
at myLibrary.Material.ViewTreeSpace.ViewingTree.InitializeComponent()
at myLibrary.Material.ViewTreeSpace.ViewingTree..ctor()
at myLibrary.Material.ViewTreeSpace.ImportedTree..ctor() in c:\..\ImportedTree.cs:line 51

From what I could find, it isn't possible to inherit a XAML class from a different assembly. (ie Answer for "The component does not have a resource identified by the URI Apparently, this has been a problem since 2008 .

Edit 2:

Using @Liju's second answer, I tried setting the ResourceDictionary, but it says it fails to load the resource.

System.InvalidOperationException: ResourceDictionary LoadFrom operation failed with URI 'pack://application:,,,/myLibrary;component/Material/View Tree/ViewingTree.xaml'.
at System.Windows.ResourceDictionary.set_Source(Uri value)
at myLibrary.Material.ViewTreeSpace.ImportedTree..ctor() in c:\..\ImportedTree.cs:line 59

Answer 1

You can use the x:FieldModifier attribute as Public x:FieldModifier="public"

The default fieldmodifier value is 'not public'.

http://msdn.microsoft.com/en-us/library/vstudio/aa970905(v=vs.90).aspx

Answer 2

I assume you are getting this error at runtime. If then, load the treeview resource explicitly in the derived constructor
Sample code:

    ResourceDictionary treeResource = new ResourceDictionary
    {
        Source = new Uri(@"pack://application:,,,/<<AssemblyName>>;component/<<Path to the xaml to load>>")
};
    this.Resources.MergedDictionaries.Add(treeResource);

Hope this helps!