Binding WPF Treeview using linq query

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WPF

LINQ

I have this 4 table in SQL Server 2012
DepartmentsTbl

DepID ------- DepName
1 ------- Human Resources
2 ------- Financial Management
SpecialTbls:

SpclID ------- SpclName
1 ------- Manager
2 ------- Secretary
3 ------- Data entry
EmployeesTbl:

EmpID ------- EmpName
1 ------- Jack
2 ------- Mark
3 ------- Sara
JobDescriptionTbls:

JDID ------- EmpID ------- DepID ------- SpclID
1 ------- 1 ------- 1 ------- 1
2 ------- 2 ------- 1 ------- 2
3 ------- 2 ------- 1 ------- 3

Note (some times The Departments has no employees & also must be appear in the treeview)

And I want to show my data in treeview according to Departments names such as that

DepName ------- first node SpecialName --- Second node EmpFullName --- Third node

I use Linq query to get my data and XAML like that:

<TreeView.ItemTemplate>
                    <HierarchicalDataTemplate ItemsSource="{Binding Path=DepartmentsTbls}">
                        <TextBlock Text="{Binding Path=DepName}" Foreground="#FFF59E13" />
                        <HierarchicalDataTemplate.ItemTemplate>
                            <DataTemplate>
                                <TextBlock Text="{Binding Path=SpecialName}" Foreground="White" />
                            </DataTemplate>
                            <HierarchicalDataTemplate.ItemTemplate>
                                <DataTemplate>
                                    <TextBlock Text="{Binding Path=EmpFullName}" Foreground="White" />
                                </DataTemplate>
                            </HierarchicalDataTemplate.ItemTemplate>
                        </HierarchicalDataTemplate.ItemTemplate>
                </TreeView.ItemTemplate>
var Employees = (from spcl in menof.SpecailTbls
                         join deps in menof.DepartmentsTbls
                         on spcl.SoecialID equals deps.DepID
                         //from deps in menof.DepartmentsTbls
                         join eJD in menof.EmpJobDescriptionTbls
                         on deps.DepID equals eJD.DepID
                         join emps in menof.EmployeesTbles
                         on eJD.EmpID equals emps.EmpID
                         select new { spcl.SpecialName,deps.DepName,emps.EmpFullName }).ToList();
        tvEmpsName.ItemsSource = Employees;

But my data doesn't appear correctly only first node appear. So my question is where is the wrong here. Thanks.