Xaml Data Binding

I have the below xaml that I am trying to bind to my class. I am having trouble getting the values to show up. Can anyone point me in the direction of what I am missing. Thank you in advance.

 Dim frm As New EditPart
    frm.DataContext = New SelectedPart(_CPPartPicker.Selected_Part, "ABC")
    frm.Show()

 Class SelectedPart
Property Part_Key As Integer
Property Part_Id As String
Property Part_Rev As String
Property Whse As String
Property Part_Description As String
Sub New(Part As SNC.SL.Common.CP_Item.CP_Item_Lookup_Version_1Item_Lookup_Response, Whse As String)
    Part_Key = Part.ITEM_KEY
    Part_Id = Part.ITEM_ID
    Part_Rev = Part.ITEM_RVSN_ID
    Whse = Whse
    开发者_JAVA技巧Part_Description = Part.ITEM_DESC
End Sub

End Class

  <Grid x:Name="LayoutRoot" Margin="2">
    <Grid.RowDefinitions>
        <RowDefinition />
        <RowDefinition Height="Auto" />
    </Grid.RowDefinitions>
    <sdk:Label Content="{Binding Path=Part_Id, StringFormat='Part ID: \{0}'}" />
    <sdk:Label Content="{Binding Path=Part_Rev, StringFormat='Part Rev: \{0}'}" />
    <sdk:Label Content="{Binding Path=Part_Description, StringFormat='Description: \{0}'}"/>

        <Button x:Name="CancelButton" Content="Cancel" Width="75" Height="23" HorizontalAlignment="Right" Margin="0,12,0,0" Grid.Row="1" />
    <Button x:Name="OKButton" Content="OK" Width="75" Height="23" HorizontalAlignment="Right"  Margin="0,12,79,0" Grid.Row="1" />
</Grid>

In the ouput window I get the below error message:

Cannot get 'Part_Id' value (type 'System.String') from 'SNC.CommonStock.SelectedPart' (type 'SNC.CommonStock.SelectedPart'). BindingExpression: Path='Part_Id' DataItem='SNC.CommonStock.SelectedPart' (HashCode=53866394); target element is 'System.Windows.Controls.Label' (Name=''); target property is 'Content' (type 'System.Object').. System.MethodAccessException: Attempt by method 'System.Windows.CLRPropertyListener.get_Value()' to access method 'SNC.CommonStock.SelectedPart.get_Part_Id()' failed.

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The labels are all on top of one another at present, if there is no description then potentially you'll see no content. Place the labels in a StackPanel.

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I had to make the class I was binding to public