Alrighty, I've been beating my head against a wall here for some time trying to figure out how to do something that, to me at least, should be very simple.
I have a XamComboEditor that I want to function as a lookup, for lack of a better term. I need to figure out how I can pass along a foreign key value (seems like there should be a ValueMemberPath property and a Value property to accomplish what I'm after) to the XamComboEditor and get that value to change the SelectedItem and the display text appropriately. Consequently, when the user changes their selection in the XamComboEditor, I need to have that change cascade back to the field I used as the foreign key.
Simplified scenario:
An Customers table with a StateID field that references the States table that also contains a StateID field and a Name.
I want to be able to bind the StateID field from the Customers table to the StateID field in my States list which I would use as the ItemsSource property for the XamComboEditor and have the SelectedItem change appropriately.
My frustration may be due to simply not understanding Silverlight data binding well enough yet, but to date, the only way I have found to accomplish this it to perform a search of my States list to find the appropriate State item and set that as the SelectedItem programmatically. That's not so bad when you only have one XamComboEditor, but as the number of XamComboEditors increases, this is going to quickly become a pain point. I'm wondering if there's a better way for me to do this? Or will I always be stuck programmatically doing things this way for lookups?
Hi,
I couldn't quite catch what you're trying to achieve. However if you need SelectedValuePath and you're using lots of XamComboEditors you could extend the XamComboEditor and add these two properties. It should look something like the following:
public class XamComboEditorEx : XamComboEditor { public XamComboEditorEx() : base() { this.SelectionChanged += combo_SelectionChanged; } public string SelectedValuePath { get { return (string)GetValue(SelectedValuePathProperty); } set { SetValue(SelectedValuePathProperty, value); } } public static readonly DependencyProperty SelectedValuePathProperty = DependencyProperty.Register("SelectedValuePath", typeof(string), typeof(XamComboEditorEx), new PropertyMetadata(new PropertyChangedCallback(SelectedValuePath_Changed))); public object SelectedValue { get { return (object)GetValue(SelectedValueProperty); } set { SetValue(SelectedValueProperty, value); } } public static readonly DependencyProperty SelectedValueProperty = DependencyProperty.Register("SelectedValue", typeof(object), typeof(XamComboEditorEx), null); private static void SelectedValuePath_Changed(DependencyObject d, DependencyPropertyChangedEventArgs e) { var combo = d as XamComboEditorEx; if (combo != null) { combo.ResetSelectedValue(); } } static void combo_SelectionChanged(object sender, EventArgs e) { var combo = sender as XamComboEditorEx; if (combo != null) combo.ResetSelectedValue(); } private void ResetSelectedValue() { if (this.SelectedItem != null) this.SelectedValue = this.SelectedItem.GetType().GetProperty(this.SelectedValuePath).GetValue(this.SelectedItem, null); } }
HTH,
Yeah, sorry about the confusion. I'm kind of new to the Silverlight arena and was looking for the way we used to do things in some of the older Infragistics WinForms controls for combo editors. Basically being able to set a DisplayMember and ValueMember property on the ComboEditor, set the DataSource for it and be able to bind the Value property to some field.
Anyway, I'll try adding what you've suggested and see if that works for me.
As a suggestion, though, since this seems to be a common occurence in business applications and the code doesn't look too bad, maybe you guys would consider including it as part of the standard feature for the XamComboEditor in the Silverlight control suite?
Hi Konstantin,
I am binding to the XamCombo editor as below
<custom:XamComboEditorEx
x:Name="cmb_FieldList1" SelectionChanged="cmb_FieldList1_SelectionChanged" SelectedValueX="{Binding diag:PresentationTraceSources.TraceLevel=High,Path=Field}" SelectedValuePath="Urn" DisplayMemberPath="DisplayName" ItemsSource="{Binding Path=DataContext.DisplayFields, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type UserControl}}}" Margin="0,0,3,0" Width="100" IsEditable="True" AutoComplete="True" MaxDropDownHeight="250" />
I have used the code from your zip file. XamComboEditor's ItemsSource property is set and the items are displayed as expected but the binding to the SelectedValue does not seem to work. The setter on the SelectedValue dependency property is not called. The code for binding is as above. I have tried everything thing but to no avail
What do you recommend as a fix?
Thanks
Sean
Hello Sean,
It has been a while since you have made your post, in case you still need support I will be glad to assist you further. I suppose the other community members can benefit from this answer as well. I have been looking into your post, but it seems like that I am missing something in your scenario, so if this is still an issue for you, could you please send an isolated sample project, where the issue is reproduced, so I can investigate it further for you.
Feel free to write me if you have further questions.
Hi !
Sorry, but the function SelectedValue doesn't work at all for me ! I can't get/set a value to my XamComboEditor.
I need to set a default value. I have a XamComboEditor which is binded to a storage procedure(which give me an ID and a Name).
I want to get the ID and display the linked Name in the XamComboEditor as default value.
Example:
Constructor()
{
InitialiseComponent();
myxamcombo.SelectedValue = myobject.ID;
myxamcombo.DisplayValue = myobject.Name;
}
Regards,
Luc
Hello Luc,
Currently the cross-platform XamComboEditor doesn't have a ValuePath or Value Property and the approach Konstantin suggested seems to be the best one for having SelecdtedValue. If it doesn't meets all your requirements, I can log a Product Idea on your nehalf for adding a SelectedValue Property to the XamComboEditor in our future versions.
Looking forward for your reply.
hello Stefan !
Thank you for your answer.
Well, I can't wait the future version of XamComboEditor, so do you have another way than Emptytext to give a default value to a XamComboEditor ?
Currently the best way to achieve the functionality you want is to use the EmptyText. You can also set the SelectedValue Property, but this way the value should exist in the ItemsSource.