WPF : Databinding lookup

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I am new to WPF and have a data binding problem that i am not able to solve. Searching of google didn't help.

There are 2 collections
1) MainCol : has 2 properties: Id and Name.
2) DetailsCol : has 3 properties: Id, Description and Amount.
For each record on MainCol there is exactly one record in DetailsCol identified by Id column. For various reasons i am not able to Description and Amount to MainCol.

I have an itemscontrol that is bound to a MainCol. There is a datatemplate that has 2 textboxes that display Id and Name. How do get the corresponding value Description and Amount from DetailsCol and show it along with Id and Name.

<ItemsControl ItemsSource="{Binding Path=MainCol}" >
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding Path=Id}" ></TextBlock>
            <TextBlock Text="{Binding Path=Name}" ></TextBlock>
            <!-- How to show Description and Amount here by looking up the Id value -->
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

Note:- MainCol has 5 items and DetailsCol has 10 items. I want to show only those 5 items in MainCol.

Posted 12-Jan-11 7:43am

lejomonc

Updated 12-Jan-11 14:14pm

v6

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AspDotNetDev 12-Jan-11 17:02pm

Are these "collections" in the database? What part are you having trouble with? Can't you just add 2 new properties to your object: Description and Amount? Why store a 1 to 1 object in a different place?

lejomonc 12-Jan-11 20:13pm

yes, both collections are in database, but populated to List<customobject>. For performance reasons i am not able to add Description and Amount to MainCol.
Issue is, when Id and Name is getting rendered dynamically, how do i use the value of Id to lookup DetailsCol to get the corresponding Description and Amount. What should be the approach and syntax of binding.

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Venkatesh Mookkan · Answer 1 · 2011-01-12T16:02:00

Solution 1

You need to use MultiBinding with the combination of Converters in this case.

It would be complex on your case. But MultiBinding is the way to go.

- Add MultiBinding and binding MainCol and DetailCol
- Write a Converter to read both and return as some class which has properties of what you want like,

FinalData class:
- ID (MainCol)
- Name (MainCol)
- Description (DetailCol)
- Amount (DetailCol)

References:
Silverlight MultiBindings, How to attach multiple bindings to a single property.[^]

Even though it is in Silverlight, the concept is same.

Posted 12-Jan-11 16:02pm

Venkatesh Mookkan

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lejomonc 14-Jan-11 3:30am

Thank you for reponse. Instead of returning the an object that combines data from both collection, I returned the data from DetailsCol alone. Now the problem is since the datacontext has changed due to multi binding, how do i refer to the original datacontext
-------------------------------------------------------------------
<itemscontrol itemssource="{Binding Path=MainCol}">
<itemscontrol.itemtemplate>
<datatemplate>
<stackpanel>
<stackpanel.datacontext>
<multibinding converter="{StaticResource customConverter}">
<binding path="Id"></binding>
<binding path="DataContext.DetailsCol" relativesource="{RelativeSource FindAncestor, AncestorType={x:Type Window}}" />

</multibinding>
</stackpanel.datacontext>

<textblock text="{Binding Path=Id}"></textblock>

<textblock text="{Binding Path=Description}"></textblock>
<textblock text="{Binding Path=Amount}"></textblock>
</stackpanel></datatemplate>
</itemscontrol.itemtemplate>
</itemscontrol>
-------------------------------------------------------------------

I tried
<textblock text="{Binding Path=ItemsSource.CurrentItem.Name, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ItemsControl}}}"></textblock>

But this always returns Name corresponding to the value the first item in MainCol. Not the one corresponding to the loops current item. How do i get the original databinding context?

WPF : Databinding lookup

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Solution 1

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WPF : Databinding lookup

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