Question

this is the Book class
Book{BookId, Title, Category, Quantity};
So, how would i select only one object from each category using linq query?
i tryed like this,

this.catagoryList.DataContext = ldc.Books.Distinct(); //categoryList is a ComboBox

but you know it doesn’t work. All of these objects are unique, so it shows same category for many time.
Actually i want it like GroupBy, but i would like to select only one objects from each group to show unique categories in the ComboBox. Thanks.

XAML:

    <DataTemplate x:Key="CatagoryTemplate">
          <StackPanel Orientation="Horizontal">
            <TextBlock Text="{Binding Path=Catagory}"/>
          </StackPanel>
    </DataTemplate>
...
 <ComboBox Name="catagoryList" ItemsSource="{Binding}" ItemTemplate="{StaticResource CatagoryTemplate}" SelectionChanged="catagoryList_SelectionChanged" IsSynchronizedWithCurrentItem="True"/>
...

Answer 1

this.catagoryList.DataContext = ldc.Books.Select(b => b.Category).Distinct();

If you don’t want to change your template:

catagoryList.DataContext = ldc.Books.Select(b => b.Category)
                                    .Distinct()
                                    .Select(c => new { Catagory = c });

But I think it’s better to change template to match strings.

<DataTemplate x:Key="CatagoryTemplate">
      <StackPanel Orientation="Horizontal">
        <TextBlock Text="{Binding}"/>
      </StackPanel>
</DataTemplate>