Dealing with Suggestion Box in Xamarin ComboBox (SfComboBox)

13 May 202124 minutes to read

Suggestion box is a drop-down list box, which displays the filtered suggestions inside a popup. This section explains the properties that deals with the drop-down list in SfComboBox control.

Suggestion box placement mode

The drop-down that shows the filtered items will be placed automatically based on the available space and can also be customized using the SuggestionBoxPlacement property.

Top - Drop-down will be placed above the text box.

Bottom - Drop-down will be placed below the text box.

Auto - Drop-down will be placed based on the available space either top or bottom of the text box.

None - Drop-down will not be shown with the filtered items.

<StackLayout VerticalOptions="Center" HorizontalOptions="Center" Padding="30">
    <combobox:SfComboBox HeightRequest="40" SuggestionBoxPlacement="Top" x:Name="comboBox">
        <combobox:SfComboBox.ComboBoxSource>
            <ListCollection:List x:TypeArguments="x:String">
                <x:String> Uganda </x:String>
                <x:String> Ukraine </x:String>
                <x:String> United Arab Emirates </x:String>
                <x:String> United Kingdom </x:String>
                <x:String> United States </x:String>
            </ListCollection:List>
        </combobox:SfComboBox.ComboBoxSource>
    </combobox:SfComboBox>                   
</StackLayout>
StackLayout layout = new StackLayout() 
{ 
    VerticalOptions = LayoutOptions.Start, 
    HorizontalOptions = LayoutOptions.Start, 
    Padding = new Thickness(30) 
};	
List<String> countryNames = new List<String>();
countryNames.Add("Uganda");
countryNames.Add("Ukraine");
countryNames.Add("United Arab Emirates");
countryNames.Add("United Kingdom");
countryNames.Add("United States");

SfComboBox comboBox = new SfComboBox();
comboBox.HeightRequest = 40;
comboBox.ComboBoxSource = countryNames;
comboBox.SuggestionBoxPlacement = SuggestionBoxPlacement.Top;
layout.Children.Add(comboBox); 
Content = layout;

Top placement image

Maximum suggestion box height

The maximum height of the suggestion box in the SfComboBox control can be varied using the MaximumDropDownHeight property.

<StackLayout VerticalOptions="Start" HorizontalOptions="Start" Padding="30">
    <combobox:SfComboBox HeightRequest="40" x:Name="comboBox" MaximumDropDownHeight="100">
        <combobox:SfComboBox.ComboBoxSource>
            <ListCollection:List x:TypeArguments="x:String">
                <x:String> Great Britain </x:String>
                <x:String> Uganda </x:String>
                <x:String> Ukraine </x:String>
                <x:String> Canada </x:String>
                <x:String> United Arab Emirates </x:String>
                <x:String> France </x:String>
                <x:String> United Kingdom </x:String>
                <x:String> China </x:String>
                <x:String> United States </x:String>
                <x:String> Japan </x:String>
            </ListCollection:List>
        </combobox:SfComboBox.ComboBoxSource>
    </combobox:SfComboBox>                           
</StackLayout>
StackLayout layout = new StackLayout() 
{ 
    VerticalOptions = LayoutOptions.Start, 
    HorizontalOptions = LayoutOptions.Start, 
    Padding = new Thickness(30) 
};

List<String> countryNames = new List<String>();
countryNames.Add("Great Britain");
countryNames.Add("Uganda");
countryNames.Add("Ukraine");
countryNames.Add("Canada");
countryNames.Add("United Arab Emirates");
countryNames.Add("France");
countryNames.Add("United Kingdom");
countryNames.Add("China");
countryNames.Add("United States");
countryNames.Add("Japan");

SfComboBox comboBox = new SfComboBox();
comboBox.HeightRequest = 40;
comboBox.ComboBoxSource = countryNames;
comboBox.MaximumDropDownHeight = 100;
layout.Children.Add(comboBox); 
Content = layout;

Maximum dropdown height image

Opening suggestion box on focus

Suggestion box can be shown whenever the control receives focus using the ShowSuggestionsOnFocus property. Suggestion list is the complete list of data source.

<StackLayout VerticalOptions="Start" HorizontalOptions="Start" Padding="30">
    <combobox:SfComboBox HeightRequest="40" x:Name="comboBox" ShowSuggestionsOnFocus="true">
        <combobox:SfComboBox.ComboBoxSource>
            <ListCollection:List x:TypeArguments="x:String">
                <x:String> Great Britain </x:String>
                <x:String> Canada </x:String>
                <x:String> France </x:String>
                <x:String> China </x:String>
                <x:String> Japan </x:String>
            </ListCollection:List>
        </combobox:SfComboBox.ComboBoxSource>
    </combobox:SfComboBox>                                       
</StackLayout>
StackLayout layout = new StackLayout() 
{ 
    VerticalOptions = LayoutOptions.Start, 
    HorizontalOptions = LayoutOptions.Start, 
    Padding = new Thickness(30) 
};	
List<String> countryNames = new List<String>();
countryNames.Add("Great Britain");
countryNames.Add("Canada");
countryNames.Add("France");
countryNames.Add("China");
countryNames.Add("Japan");

SfComboBox comboBox = new SfComboBox();
comboBox.HeightRequest = 40;
comboBox.ComboBoxSource = countryNames;
comboBox.ShowSuggestionsOnFocus = true;
comboBox.IsEditableMode = true;
comboBox.SelectionChanged += (sender, e) => 
{
	DisplayAlert("Selection Changed", "Selected Value: " + comboBox.SelectedValue.ToString(), "OK"); 
};

layout.Children.Add(comboBox); 
Content = layout;

Show suggestion onfocus image

Delay opening suggestion box

The PopupDelay property is used to delay the suggestion box opening process. It gets milliseconds as input in integer data type.
In this example, a time duration of 3 seconds is set to popup delay.

<StackLayout VerticalOptions="StartAndExpand" HorizontalOptions="StartAndExpand" Padding="30">
    <combobox:SfComboBox HeightRequest="40" x:Name="comboBox" PopupDelay="3000">
        <combobox:SfComboBox.ComboBoxSource>
            <ListCollection:List x:TypeArguments="x:String">
                <x:String> Uganda </x:String>
                <x:String> Ukraine </x:String>
                <x:String> United Arab Emirates </x:String>
                <x:String> United Kingdom </x:String>
                <x:String> United States </x:String>
            </ListCollection:List>
        </combobox:SfComboBox.ComboBoxSource>
    </combobox:SfComboBox>                                            
</StackLayout>
StackLayout layout = new StackLayout() 
{ 
    VerticalOptions = LayoutOptions.Start, 
    HorizontalOptions = LayoutOptions.Start, 
    Padding = new Thickness(30) 
};	
List<String> countryNames = new List<String>();
countryNames.Add("Uganda");
countryNames.Add("Ukraine");
countryNames.Add("United Arab Emirates");
countryNames.Add("United Kingdom");
countryNames.Add("United States");

SfComboBox comboBox = new SfComboBox();
comboBox.HeightRequest = 40;
comboBox.ComboBoxSource = countryNames;
comboBox.PopupDelay = 3000;

layout.Children.Add(comboBox); 
Content = layout;

Delay before searching algorithm starts

The SearchDelay property is used to delay the searching algorithm process. It gets milliseconds as input in integer data type.

In this example, a time duration of 3 seconds is set to search delay.

<StackLayout VerticalOptions="StartAndExpand" HorizontalOptions="StartAndExpand" Padding="30">
    <combobox:SfComboBox HeightRequest="40" x:Name="comboBox" SearchDelay="3000">
        <combobox:SfComboBox.ComboBoxSource>
            <ListCollection:List x:TypeArguments="x:String">
                <x:String> Uganda </x:String>
                <x:String> Ukraine </x:String>
                <x:String> United Arab Emirates </x:String>
                <x:String> United Kingdom </x:String>
                <x:String> United States </x:String>
            </ListCollection:List>
        </combobox:SfComboBox.ComboBoxSource>
    </combobox:SfComboBox>                                            
</StackLayout>
StackLayout layout = new StackLayout() 
    { 
        VerticalOptions = LayoutOptions.Start, 
        HorizontalOptions = LayoutOptions.Start, 
        Padding = new Thickness(30) 
    };	
    List<String> countryNames = new List<String>();
    countryNames.Add("Uganda");
    countryNames.Add("Ukraine");
    countryNames.Add("United Arab Emirates");
    countryNames.Add("United Kingdom");
    countryNames.Add("United States");
    
    SfComboBox comboBox = new SfComboBox();
    comboBox.HeightRequest = 40;
    comboBox.ComboBoxSource = countryNames;
    comboBox.SearchDelay = 3000;
    
    layout.Children.Add(comboBox); 
    Content = layout;

Avoid opening suggestion box

To avoid the drop down open, you can set the SuggestionBoxPlacement API to None.

<StackLayout VerticalOptions="StartAndExpand" HorizontalOptions="StartAndExpand" Padding="30">
    <combobox:SfComboBox HeightRequest="40" x:Name="comboBox" SuggestionBoxPlacement="None">
        <combobox:SfComboBox.ComboBoxSource>
            <ListCollection:List x:TypeArguments="x:String">
                <x:String> Uganda </x:String>
                <x:String> Ukraine </x:String>
                <x:String> United Arab Emirates </x:String>
                <x:String> United Kingdom </x:String>
                <x:String> United States </x:String>
            </ListCollection:List>
        </combobox:SfComboBox.ComboBoxSource>
    </combobox:SfComboBox>                             
</StackLayout>
StackLayout layout = new StackLayout() 
{ 
    VerticalOptions = LayoutOptions.Start, 
    HorizontalOptions = LayoutOptions.Start, 
    Padding = new Thickness(30) 
};	

List<String> countryNames = new List<String>();
countryNames.Add("Uganda");
countryNames.Add("Ukraine");
countryNames.Add("United Arab Emirates");
countryNames.Add("United Kingdom");
countryNames.Add("United States");

SfComboBox comboBox = new SfComboBox();
comboBox.HeightRequest = 40;
comboBox.SuggestionBoxPlacement = SuggestionBoxPlacement.None;
comboBox.ComboBoxSource = countryNames;
layout.Children.Add(comboBox); 
Content = layout;

Retrieve the filter suggestion items

There are two ways to get the filtered suggestion items from SfComboBox.
You can use the FilteredItems API in SfComboBox to access filtered suggestions items. You can get the filtered items when IsEditableMode is true and AllowFiltering is true.

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:local="clr-namespace:SfComboBox_Sample"
             xmlns:d="http://xamarin.com/schemas/2014/forms/design"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             mc:Ignorable="d"
             xmlns:combobox="clr-namespace:Syncfusion.XForms.ComboBox;assembly=Syncfusion.SfComboBox.XForms"
             x:Class="SfComboBox_Sample.MainPage">
    <ContentPage.BindingContext>
        <local:EmployeeViewModel/>
    </ContentPage.BindingContext>
    <StackLayout VerticalOptions="StartAndExpand" 
                 HorizontalOptions="StartAndExpand" 
                 Padding="30">
        <combobox:SfComboBox HeightRequest="40" 
                             x:Name="comboBox" 
                             IsEditableMode="True" 
                             AllowFiltering="True" 
                             SuggestionMode="Contains"
                             SuggestionBoxPlacement="None"
                             DisplayMemberPath="Name"
                             DataSource="{Binding EmployeeCollection}"
                             FilteredItems="{Binding Items,Mode=TwoWay}"/>
        <StackLayout Orientation="Vertical" Margin="0,50,0,0">
            <Label Text="Filtered Items" 
               FontSize="20" 
               FontAttributes="Bold" 
               TextColor="Green"/>
            <ListView 
            x:Name="MainListView" 
            ItemsSource="{Binding Items}"
            RowHeight="30">
                <ListView.ItemTemplate>
                    <DataTemplate>
                        <ViewCell>
                            <StackLayout Orientation="Horizontal">
                                <Label Text="{Binding Name}" />
                            </StackLayout>
                        </ViewCell>
                    </DataTemplate>
                </ListView.ItemTemplate>
            </ListView>
        </StackLayout>
    </StackLayout>
</ContentPage>
using Syncfusion.XForms.ComboBox;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using Xamarin.Forms;

namespace SfComboBox_Sample
{
    public partial class MainPage : ContentPage
    {
        public MainPage()
        {
            InitializeComponent();
            EmployeeViewModel viewModel = new EmployeeViewModel();
            this.BindingContext = viewModel;
            StackLayout stackLayout = new StackLayout()
            {
                VerticalOptions = LayoutOptions.Start,
                HorizontalOptions = LayoutOptions.Start,
                Padding = new Thickness(30)
            };

            SfComboBox comboBox = new SfComboBox()
            {
                HeightRequest = 40,
                WidthRequest = 100,
                IsEditableMode = true,
                AllowFiltering = true,
                DisplayMemberPath = "Name",
                SuggestionBoxPlacement = SuggestionBoxPlacement.None,
                SuggestionMode = SuggestionMode.Contains,
                DataSource = viewModel.EmployeeCollection
            };

            Binding filteredItemsBinding  = new Binding();
            filteredItemsBinding .Source = viewModel;
            filteredItemsBinding .Path = "Items";
            filteredItemsBinding .Mode = BindingMode.TwoWay;
            comboBox.SetBinding(SfComboBox.FilteredItemsProperty, filteredItemsBinding);
            StackLayout stack = new StackLayout()
            {
                Orientation = StackOrientation.Vertical,
                Margin = new Thickness(0, 50, 0, 0)
            };

            Label filteredItemsLabel  = new Label()
            {
                Text = "Filtered Items",
                FontSize = 20,
                FontAttributes = FontAttributes.Bold,
                TextColor = Color.Green
            };

            ListView MainListView = new ListView()
            {
                RowHeight = 30
            };

            Binding itemSource_binding  = new Binding();
            itemSource_binding.Source = viewModel;
            itemSource_binding.Path = "Items";
            MainListView.SetBinding(ListView.ItemsSourceProperty, itemSource_binding);

            DataTemplate itemTemplate = new DataTemplate(() =>
            {
                StackLayout layout = new StackLayout()
                {
                    Orientation = StackOrientation.Horizontal
                };

                Label nameLabel = new Label();
                nameLabel.SetBinding(Label.TextProperty, "Name");
                layout.Children.Add(nameLabel);

                return new ViewCell { View = layout };
            });

            MainListView.ItemTemplate = itemTemplate;

            stack.Children.Add(filteredItemsLabel );
            stack.Children.Add(MainListView);
            stackLayout.Children.Add(comboBox);
            stackLayout.Children.Add(stack);
            this.Content = stackLayout;
        }
    }

    public class Employee
    {
        private int id;
        public int ID
        {
            get { return id; }
            set { id = value; }
        }
        private string name;
        public string Name
        {
            get { return name; }
            set { name = value; }
        }
    }

    public class EmployeeViewModel : INotifyPropertyChanged
    {
        private IEnumerable<object> items;

        public IEnumerable<object> Items
        {
            get { return items; }
            set
            {
                items = value;
                NotifyPropertyChanged();
            }
        }


        public event PropertyChangedEventHandler PropertyChanged;

        private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        private ObservableCollection<Employee> employeeCollection;
        public ObservableCollection<Employee> EmployeeCollection
        {
            get { return employeeCollection; }
            set { employeeCollection = value; }
        }
        public EmployeeViewModel()
        {
            employeeCollection = new ObservableCollection<Employee>();
            employeeCollection.Add(new Employee() { ID = 1, Name = "Eric" });
            employeeCollection.Add(new Employee() { ID = 2, Name = "James" });
            employeeCollection.Add(new Employee() { ID = 3, Name = "Jacob" });
            employeeCollection.Add(new Employee() { ID = 4, Name = "Lucas" });
            employeeCollection.Add(new Employee() { ID = 5, Name = "Mark" });
            employeeCollection.Add(new Employee() { ID = 6, Name = "Aldan" });
            employeeCollection.Add(new Employee() { ID = 7, Name = "Aldrin" });
            employeeCollection.Add(new Employee() { ID = 8, Name = "Alan" });
            employeeCollection.Add(new Employee() { ID = 9, Name = "Aaron" });
        }
    }
}

The other way to get a filtered suggestion item is an event called FilterCollectionChanged. This event is triggered when the SfComboBox suggestions have been changed. You can get the filtered items from the FilterCollectionChanged event value argument.

Members Description
Value Shows filtered items in SfComboBox control.

The following code snippet describes how to trigger an event called FilterCollectionChanged.

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:local="clr-namespace:SfComboBox_Sample"
             xmlns:d="http://xamarin.com/schemas/2014/forms/design"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             mc:Ignorable="d"
             xmlns:combobox="clr-namespace:Syncfusion.XForms.ComboBox;assembly=Syncfusion.SfComboBox.XForms"
             x:Class="SfComboBox_Sample.MainPage">
    <ContentPage.BindingContext>
        <local:EmployeeViewModel/>
    </ContentPage.BindingContext>
    <StackLayout VerticalOptions="StartAndExpand" 
                 HorizontalOptions="StartAndExpand" 
                 Padding="30">
        <combobox:SfComboBox HeightRequest="40" 
                             x:Name="comboBox" 
                             IsEditableMode="True" 
                             AllowFiltering="True" 
                             SuggestionMode="Contains"
                             SuggestionBoxPlacement="None"
                             DisplayMemberPath="Name"
                             DataSource="{Binding EmployeeCollection}"
                             FilteredItems="{Binding Items,Mode=TwoWay}"
                             FilterCollectionChanged="ComboBox_FilterCollectionChanged"/>
        <StackLayout Orientation="Vertical" Margin="0,50,0,0">
            <Label Text="Filtered Items" 
               FontSize="20" 
               FontAttributes="Bold" 
               TextColor="Green"/>
            <ListView 
            x:Name="MainListView" 
            RowHeight="30">
                <ListView.ItemTemplate>
                    <DataTemplate>
                        <ViewCell>
                            <StackLayout Orientation="Horizontal">
                                <Label Text="{Binding Name}" />
                            </StackLayout>
                        </ViewCell>
                    </DataTemplate>
                </ListView.ItemTemplate>
            </ListView>
        </StackLayout>
    </StackLayout>
</ContentPage>
using Syncfusion.XForms.ComboBox;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using Xamarin.Forms;

namespace SfComboBox_Sample
{
    public partial class MainPage : ContentPage
    {
        ListView MainListView;
        public MainPage()
        {
            InitializeComponent();
            EmployeeViewModel viewModel = new EmployeeViewModel();
            this.BindingContext = viewModel;
            StackLayout stackLayout = new StackLayout()
            {
                VerticalOptions = LayoutOptions.Start,
                HorizontalOptions = LayoutOptions.Start,
                Padding = new Thickness(30)
            };

            SfComboBox comboBox = new SfComboBox()
            {
                HeightRequest = 40,
                WidthRequest = 100,
                IsEditableMode = true,
                AllowFiltering = true,
                DisplayMemberPath = "Name",
                SuggestionBoxPlacement = SuggestionBoxPlacement.None,
                SuggestionMode = SuggestionMode.Contains,
                DataSource = viewModel.EmployeeCollection
            };

            comboBox.FilterCollectionChanged += ComboBox_FilterCollectionChanged;
            Binding filteredItemsBinding  = new Binding();
            filteredItemsBinding .Source = viewModel;
            filteredItemsBinding .Path = "Items";
            filteredItemsBinding .Mode = BindingMode.TwoWay;
            comboBox.SetBinding(SfComboBox.FilteredItemsProperty, filteredItemsBinding );
            StackLayout stack = new StackLayout()
            {
                Orientation = StackOrientation.Vertical,
                Margin = new Thickness(0, 50, 0, 0)
            };

            Label filteredItemsLabel  = new Label()
            {
                Text = "Filtered Items",
                FontSize = 20,
                FontAttributes = FontAttributes.Bold,
                TextColor = Color.Green
            };

            MainListView = new ListView()
            {
                RowHeight = 30
            };

            DataTemplate itemTemplate = new DataTemplate(() =>
            {
                StackLayout layout = new StackLayout()
                {
                    Orientation = StackOrientation.Horizontal
                };

                Label nameLabel = new Label();
                nameLabel.SetBinding(Label.TextProperty, "Name");
                layout.Children.Add(nameLabel);

                return new ViewCell { View = layout };
            });

            MainListView.ItemTemplate = itemTemplate;

            stack.Children.Add(filteredItemsLabel );
            stack.Children.Add(MainListView);
            stackLayout.Children.Add(comboBox);
            stackLayout.Children.Add(stack);
            this.Content = stackLayout;
        }
        private void ComboBox_FilterCollectionChanged(object sender, FilterCollectionChangedEventArgs e)
        {
            MainListView.ItemsSource = (IEnumerable)e.Value;
        }
    }

    public class Employee
    {
        private int id;
        public int ID
        {
            get { return id; }
            set { id = value; }
        }
        private string name;
        public string Name
        {
            get { return name; }
            set { name = value; }
        }
    }

    public class EmployeeViewModel : INotifyPropertyChanged
    {
        private IEnumerable<object> items;

        public IEnumerable<object> Items
        {
            get { return items; }
            set
            {
                items = value;
                NotifyPropertyChanged();
            }
        }


        public event PropertyChangedEventHandler PropertyChanged;

        private void NotifyPropertyChanged([CallerMemberName] String propertyName = "")
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        private ObservableCollection<Employee> employeeCollection;
        public ObservableCollection<Employee> EmployeeCollection
        {
            get { return employeeCollection; }
            set { employeeCollection = value; }
        }
        public EmployeeViewModel()
        {
            employeeCollection = new ObservableCollection<Employee>();
            employeeCollection.Add(new Employee() { ID = 1, Name = "Eric" });
            employeeCollection.Add(new Employee() { ID = 2, Name = "James" });
            employeeCollection.Add(new Employee() { ID = 3, Name = "Jacob" });
            employeeCollection.Add(new Employee() { ID = 4, Name = "Lucas" });
            employeeCollection.Add(new Employee() { ID = 5, Name = "Mark" });
            employeeCollection.Add(new Employee() { ID = 6, Name = "Aldan" });
            employeeCollection.Add(new Employee() { ID = 7, Name = "Aldrin" });
            employeeCollection.Add(new Employee() { ID = 8, Name = "Alan" });
            employeeCollection.Add(new Employee() { ID = 9, Name = "Aaron" });
        }
    }
}

Filtered_Items_Image