You're welcome glad I could help.<g>

This is a good read on the binding stuff:

http://blogs.msdn.com/wpfsdk/archive/2006/10/19/wpf-basic-data-binding-faq.aspx

>DUDE!! You are super smart with stuff.
>
>It works perfectly now!
>
>When you said "You can't bind to fields so make this a Property", that was something I did not realize, and it made all the difference in the world. I was driving in my car (and looking at the UT web site on my iPhone) when I saw your reply. I was so wanting to get to my computer to test it, but I could not get to it until this morning.
>
>Thanks to you, I am now doing all binding in XAML, and it *DOES* update the Customer object of the Job based on the Customer object chosen in the ComboBox. No code-behind at all.
>
>I am not yet totally clear on the Property vs. Field thing, so I need to learn when which one to use when. For instance, should the Job object defined in the Window class be a Field or a Property and should it be public or private?
>
>
>John - I cannot tell you how happy I am to get to this place! I truly say 'Thank you!' for taking so much time with me on this.
>
>
>Some important things to get this working were:
>---------------------------------------------------------------------------
> 0. Understand that you have to change the Customer object reference on the Job, not the foreign key property cust_num on the Job object
> 1. Exposing custs as a *PROPERTY* on the Window class so I can bind to it in XAML
> 2. setting the ComboBox SelectedValue as the Customer object (of the Job Object) not the cust_num
> 3. Apparently, *NOT* setting a value for SelectedValuePath... it seems to default to the object of the ItemsSource collection, and I guess that is why it works 2-way with SelectedValue (the Customer reference on the Job object)
>
>
>Here's the final XAML code:
>

>    <ComboBox x:Name="dropdownCustomer" IsSynchronizedWithCurrentItem="True" AllowDrop="True"
>              ItemsSource="{Binding Path=custs, ElementName=winJobEdit}"
>              DisplayMemberPath="company"
>              SelectedValue="{Binding Path=Customer, Mode=TwoWay}"
>              />
>

>
>And the very simple code-behind to support it all
>

>namespace wpf2
>{
>    public partial class WindowJobEdit : Window
>    {
>        private string _JobNo;
>
>        DataClasses1DataContext ctx = new DataClasses1DataContext();
>        Job JobToEdit;
>        public IQueryable<Customer> custs {get; set;}
>
>        public WindowJobEdit(string JobNo)
>        {
>
>            custs = from c in ctx.Customers
>                         select c;
>
>            InitializeComponent();
>
>            GetJobToEdit(JobNo);
>
>            gridMain.DataContext = JobToEdit;
>
>        }
>
>
>        public void GetJobToEdit(string JobNo)
>        {
>
>            if (JobNo != null)
>            {
>               _JobNo = JobNo; // Not really sure if I need this or not
>                JobToEdit = ctx.Jobs.Single(o => o.job_num == JobNo);
>            }
>        }
>
>

>
>
>
>>>Well...The first problem I had was setting the ItemsSource in XAML. I couldn't figure it out, so I do it in the form constrctor. Seeing more of your code, I think I see a slightly diffferent structure...
>>
>>That does work fine.
>>
>>>>As far as my ComboBox goes, it is not in a UserControl, it's just a plain UI control in a HeaderedContentControl (I wonder where I learned about that), that is also in a StackPanel, that is also in a Grid. I tried to set ItemsSource="{Binding Path=custs, ElementName=______ (don't know what to put here).
>>
>>My UserControl was basically the same as your Window, it was the root element of the XAML file.
>>
>>>So, in code-behind, I set the DataContext of gridMain to a Job, and I also set the ItemsSource on the ComboBox to the full list of Customer objects (the "custs" collection). I really want to figure out setting the ItemsSource in XAML, but haven't so far.
>>
>>You can't bind to fields so make this a Property:

public IQueryable<Customer> custs { get; set;}

>>Substitute Window for UserControl:

<Window ... Name="winJobEdit"> ...

>>Note the element name being used in the binding here:

ItemsSource="{Binding Path=custs, ElementName=winJobEdit}"

>>
>>>However, that is not really the issue with the greater goal here of updating the Customer reference in a Job from the XAML binding, so I've just been letting the ItemsSource thing slide for now. But I'm certainly curious to figure it out.
>>
>>Try the code above.
>>
>>>Also, is your DataStores a collection of strings? I notice you are not having to use DisplayMemberValue and SelectedItemPath. My ItemsSource is a collection of Customer objects, so I have to specify which field on the Customer object is what part. I see that you are using SelectedValue but not the other two.
>>
>>Datastores is a collection of objects. I'm using a DataTemplate instead, but I think either way should work.

<ComboBox.ItemTemplate>
>>  <DataTemplate>
>>    <TextBlock Text="{Binding Path=company}"/>
>>  </DataTemplate>
>></ComboBox.ItemTemplate>

>>
>>>So you are able to point the ItemsSource to a Path on your UserControl, but what do I need to point to in order to get at the public custs collection?
>>
>>See above, you can't bind to a field so you have to make it a property.