How to bind to a custom event handler in XAML

Question

I am having some difficulty figuring out how to properly bind a custom event handler from my XAML instead of my code behind. In my code behind I current have this in my parent code behind:

this.stepBar.Callback = SetViewForStep;

This works fine and it will properly set the Callback event handler in my custom control which is defined as follows:

public static readonly BindableProperty CallbackProperty = BindableProperty.Create(nameof(Callback), typeof(EventHandler), typeof(StepProgressBarControl), null);

public EventHandler Callback {
            get {
                return (EventHandler)GetValue(CallbackProperty);
            } set {
                SetValue(CallbackProperty, value);
            }
        }

However, I would like to be able to define it purely in XAML the same way one might define a Click event on a button.

<StackLayout HorizontalOptions="FillAndExpand" VerticalOptions="FillAndExpand"
                     Padding="20" Spacing="20">
            <customcontrols:StepProgressBarControl 
                StepColor="LightPink" 
                Steps="5" 
                Callback="SetViewForStep"
                StepSelected="{Binding SelectedStep}" x:Name="stepBar" />
            <Label
               Text="{Binding SelectedStep, StringFormat='The Step Selected is {0}'}"
               FontAttributes="Bold"
               FontSize="Large"
               HorizontalOptions="Center"
               VerticalOptions="CenterAndExpand" />
        </StackLayout>

However, if I define it in the XAML and try to run it I get a compile error of Error XFC0009 No property, BindableProperty, or event found for "Callback", or mismatching type between value and property.

How can I create an EventHandler such that I can define its function in my xaml.cs the same way one might define a click event for a button or any other built in control that has an exposed EventHandler property?

Answer 1

Declaring Callback as event should be able to solve the problem.

Change your code in custom control as below

 public event EventHandler Callback;

In this way when we type Callback in xaml, the intellisense helps us to reference the method in page.