How to filter Xamarin.Forms ListView (SfListView) using MVVM

You can filter ListViewItems in MVVM using behavior in Xamarin.Forms SfListView.

You can also refer the following article.

https://www.syncfusion.com/kb/11478/how-to-filter-xamarin-forms-listview-sflistview-using-mvvm

XAML

Define the ContentPage behavior.

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:local="clr-namespace:ListViewXamarin"
             xmlns:sync="clr-namespace:Syncfusion.ListView.XForms;assembly=Syncfusion.SfListView.XForms"
             x:Class="ListViewXamarin.MainPage">
    <ContentPage.Behaviors>
        <local:Behavior/>
    </ContentPage.Behaviors>
    
    <ContentPage.BindingContext>
        <local:SortingFilteringViewModel/>
    </ContentPage.BindingContext>
 
    <ContentPage.Content>
        <Grid x:Name="MainGrid" Margin="{OnPlatform iOS='0,40,0,0'}">
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto" />
                <RowDefinition Height="*" />
            </Grid.RowDefinitions>
 
            <SearchBar x:Name="filterText" Placeholder="Search here to filter" />
            <sync:SfListView x:Name="listView" ItemsSource="{Binding Items}" Grid.Row="1" ItemSpacing="0,5,0,5" BackgroundColor="#F0F0F0" ItemSize="100">
                <sync:SfListView.ItemTemplate>
                    <DataTemplate x:Name="ItemTemplate" >
                        <Frame OutlineColor="#b3b3b3" Padding="2" Margin="10,0,10,0">
                            <Grid BackgroundColor="White" Padding="10">
                                <Grid.RowDefinitions>
                                    <RowDefinition Height="Auto"/>
                                    <RowDefinition Height="*"/>
                                    <RowDefinition Height="Auto"/>
                                </Grid.RowDefinitions>
                                <Label x:Name="TitleLabel" LineBreakMode="NoWrap" Text="{Binding Title}" FontAttributes="Bold" TextColor="Black"/>
                                <Label Grid.Row="1" x:Name="DescriptionLabel" Text="{Binding Description}" TextColor="Teal"/>
                                <Frame Grid.Row="2" Padding="4,2,4,2" BackgroundColor="#FFE7E8E9" HorizontalOptions="Start" VerticalOptions="End">
                                    <Label x:Name="TagLabel" LineBreakMode="NoWrap" Text="{Binding Tag}" FontSize="10" TextColor="Black"/>
                                </Frame>
                            </Grid>
                        </Frame>
                    </DataTemplate>
                </sync:SfListView.ItemTemplate>
            </sync:SfListView>
        </Grid>
    </ContentPage.Content>
</ContentPage>

C#

Trigger the TextChanged event of the SearchBar control to filter the ListView based on the SearchText. Set the Filter predicate for ListView to filter the items and call the RefreshView method.

namespace ListViewXamarin
{
    public class Behavior : Behavior<ContentPage>
    {
        SfListView ListView;
        SearchBar SearchBar;
 
        protected override void OnAttachedTo(ContentPage bindable)
        {
            ListView = bindable.FindByName<SfListView>("listView");
            SearchBar = bindable.FindByName<SearchBar>("filterText");
            SearchBar.TextChanged += SearchBar_TextChanged;
            base.OnAttachedTo(bindable);
        }
 
        private void SearchBar_TextChanged(object sender, TextChangedEventArgs e)
        {
            if (ListView.DataSource != null)
            {
                ListView.DataSource.Filter = FilterContacts;
                ListView.DataSource.RefreshFilter();
            }
            ListView.RefreshView();
        }
 
        private bool FilterContacts(object obj)
        {
            if (SearchBar == null || SearchBar.Text == null)
                return true;
 
            var taskInfo = obj as TaskInfo;
            return (taskInfo.Title.ToLower().Contains(SearchBar.Text.ToLower())
                || taskInfo.Description.ToLower().Contains(SearchBar.Text.ToLower()));
        }
    }
}

Output