Service provider is missing the INameResolver service.

happens when cross reference in place of a WPF XAML elements.

<TextBox x:Name="txtFN"
Grid.Column="1">ssssssssssss</TextBox>
<Label Target="{x:Reference txtFN}">_FirstName</Label>

This is a design time error can be ignored safely.. Verify Project target framework to 4.0 .