How to Use Behaviors to Manage ComboBox SelectionChanged Events in .NET MAUI

You can use behaviors to handle events more modularly and reusable. Behaviors allow you to encapsulate the interaction logic in a separate class, making it easy to attach to different controls. Below is an example of how you can use behaviors for the SelectionChanged event in the
.NET MAUI ComboBox.

Step 1: Create the SelectionChangedBehaviors class for the SfComboBox behavior.

C#

public class SelectionChangedBehavior : Behavior<SfComboBox>
{
   public Command Display { get; private set; }
   EmployeeViewModel employeeViewModel;
   protected override void OnAttachedTo(SfComboBox bindable)
   {
       bindable.SelectionChanged += Bindable_SelectionChanged;
       base.OnAttachedTo(bindable);
   }
   protected override void OnDetachingFrom(SfComboBox bindable)
   {
       bindable.SelectionChanged -= Bindable_SelectionChanged;
       base.OnDetachingFrom(bindable);
   }

   async void Bindable_SelectionChanged(object sender, Syncfusion.Maui.Inputs.SelectionChangedEventArgs e)
   {
       employeeViewModel = new EmployeeViewModel();
       var selectedValue = e.CurrentSelection;
       var lastItem = selectedValue.Last();
       employeeViewModel.SelectedId = new List<string>();
       foreach (var item in selectedValue)
       {
           var selectedId = (item as Employee).Id;
           if (item == lastItem)
           {
               employeeViewModel.SelectedId.Add(selectedId);
               Application.Current.MainPage.DisplayAlert("Selected Id", "The last selected ID is " + selectedId, "Ok");
           }
           else
           {
               employeeViewModel.SelectedId.Add(selectedId);
           }
       }
   }
}

Step 2: Attach the SelectionChangedBehavior to the ComboBox behaviors.

XAML

<ContentPage.BindingContext>
   <local:EmployeeViewModel/>
</ContentPage.BindingContext>

<StackLayout Padding="50,100,50,0">
   <inputs:SfComboBox x:Name="comboBox"
                      WidthRequest="200"
                      IsEditable="True"
                      SelectedIndex="2"
                      DisplayMemberPath="Name" 
                      ItemsSource="{Binding EmployeeCollection}"
                      MaxDropDownHeight = "180">
       <inputs:SfComboBox.Behaviors>
           <local:SelectionChangedBehavior/>
       </inputs:SfComboBox.Behaviors>
   </inputs:SfComboBox>
</StackLayout>

You can find the sample in the following link.

Output

Conclusion:
I hope you enjoyed learning how to use behaviors to manage the SelectionChanged event in .NET MAUI ComboBox(SfComboBox).
Refer to our .NET MAUI ComboBox feature tour page for its other groundbreaking feature representations. You can explore our .NET MAUI ComboBox documentation to understand how to present and manipulate data.

For current customers, check out our .NET MAUI components from the License and Downloads page. If you are new to Syncfusion, you can try our 30-day free trial to check out our .NET MAUI ComboBox(SfComboBox ) and other .NET MAUI components.

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