Implement Custom Filtering

Input field

The input field is just a basic Textbox we are gonna using for inputting the filter criteria value.
It is based on these components:

• Grid.Resources to define the style
• Textblock with run text
• Textbox that serves as an input field

It will look like this:

<Grid>
      <Grid.Resources>
           <Style BasedOn="{StaticResource UBIKIconStyle}"
              TargetType="FontIcon">
                <Setter Property="Foreground"
                   Value="{StaticResource UBIKMediumTextColor}" />
                <Setter Property="FontSize"
                   Value="14" />
                <Setter Property="HorizontalAlignment"
                   Value="Left" />
           </Style>
      </Grid.Resources>

      <!--  Type / Content / Buttons  -->
      <Grid.ColumnDefinitions>
             <ColumnDefinition Width="60" />
             <ColumnDefinition Width="2*" />
       </Grid.ColumnDefinitions>

      <TextBlock Margin="0,0,0,0"
           Grid.Column="0"
           Style="{StaticResource UBIKTextStyle}">
            <Run Text="Name:"/>
      </TextBlock>

     <!--  Textbox for editing  -->
     <TextBox x:Name="InputTextboxName"
          Grid.Column="1"
          Margin="0,0,0,0"
          Style="{StaticResource UBIKTextBoxStyle}">
     </TextBox>
</Grid>

EvalExpression

With this EvalExpression, we are able to combine the Input text field with the value parameter (property from the item we want to filter).

Here is the final XAML EvalExpression solution:

<controls:EvalExpression x:Name="FilterExpression"
               Context="{Binding}"
               Expression="FC1">
                    <controls:EvalExpressionParameter Name="FC1"
                   Value="{Binding ElementName=InputTextboxName, Path=Text, Converter={StaticResource StringFormatConverter}, ConverterParameter='Item.Values[&quot;NAME&quot;].ToLower().Contains(&quot;{0}&quot;.ToLower())==true'}" />
            </controls:EvalExpression>

The best solution would be to place this eval expression into the <Grid.Resources>.

To really get used to this EvalExpression we also need to configure a ListCollectionView, that would look like this:

<cv:ListCollectionView x:Key="FilterView"
               Expression="{Binding ElementName=FilterExpression, Path=Result}"
               ItemsSource="{Binding PropertyViewModel.FilterQueryResults.Items, Converter={StaticResource CollectionTruncateConverter}, ConverterParameter=200}" />