Bindable Entry is not working inside custom control in Xamarin.forms?

Question

I have an entry field inside custom control. I've created bindable property for the same.

Here's my code:

public string MyEntry
    {
        get => (string)GetValue(MyEntryProperty);
        set => SetValue(MyEntryProperty, value);
    }
    public static BindableProperty MyEntryProperty = BindableProperty.Create(
                                             propertyName: "MyEntry",
                                             returnType: typeof(string),
                                             declaringType: typeof(MyView),
                                             defaultValue: string.Empty,
                                             defaultBindingMode: BindingMode.TwoWay,
                                             propertyChanged:MyEntryPropertyChanged );


 public static void MyEntryPropertyChanged(BindableObject bindable, object oldValue, object newValue)
    {
       var cView = (MyView)bindable;
       cView.myent.Text = (string)newValue;
   }

Then on my actual view xaml:

<MyView MyEntry={Binding Something}/>

But it's not working.? Any suggestions?

Answer 1

Maybe you do not set the binding correctly. I make a code sample for your reference.

MyView:

<?xml version="1.0" encoding="utf-8" ?>
<ContentView
x:Class="XamarinDemo.Custom_Control.MyView"
xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:d="http://xamarin.com/schemas/2014/forms/design"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">

<StackLayout>
    <Entry
        x:Name="myent"
        HorizontalOptions="CenterAndExpand"
        Text="Welcome to Xamarin.Forms!"
        VerticalOptions="CenterAndExpand" />
    <Button />
</StackLayout>

</ContentView>

Code Behind: Same with yours.

 public partial class MyView : ContentView
{
    public MyView()
    {
        InitializeComponent();
    }
    public string MyEntry
    {
        get => (string)GetValue(MyEntryProperty);
        set => SetValue(MyEntryProperty, value);
    }
    public static BindableProperty MyEntryProperty = BindableProperty.Create(
                                             propertyName: "MyEntry",
                                             returnType: typeof(string),
                                             declaringType: typeof(MyView),
                                             defaultValue: string.Empty,
                                             defaultBindingMode: BindingMode.TwoWay,
                                             propertyChanged: MyEntryPropertyChanged);


    public static void MyEntryPropertyChanged(BindableObject bindable, object oldValue, object newValue)
    {
        var cView = (MyView)bindable;
        cView.myent.Text = (string)newValue;
    }
}

Usage: Page1.xaml

 <ContentPage.Content>
    <StackLayout>
        <local:MyView MyEntry="{Binding Something}"></local:MyView>
    </StackLayout>
</ContentPage.Content>

Binding:

 public partial class Page1 : ContentPage
{
    public string Something { get; set; }
    public Page1()
    {
        InitializeComponent();
        Something = "Hello";
        this.BindingContext = this;
    }
}

Screenshot:

Answer 2

I have had this issue with a custom control of mine, the main problem was my binding context was not set correctly.

The way that I used to check this was

1. I gave my control a x:name in the xaml

2. I went to the pagename.cs (code behind) in the constructor after the InializeComponents() method I typed this

Console.WriteLine($"Control-{ControlXname.BindingContext();}");
Console.WriteLine($"Page-{this.BindingContext();}");

3. After i excuted my code i headed to the output panel and i pressed ctrl + f to search for the word "Control-" and "Page-" only then i have found out that thier binding contexts was different.

Answer 3

You are only setting value to Entry, you are not reading back the changes from Entry. You have to add following in your constructor.

// ... add this in your constructor...
myent.SetBinding(Entry.TextProperty, new Binding{
    Path = "MyEntry",
    Source = this,
    Mode = BindingMode.TwoWay
});



public string MyEntry
{
    get => (string)GetValue(MyEntryProperty);
    set => SetValue(MyEntryProperty, value);
}

// remove onPropertyChanged
public static BindableProperty MyEntryProperty = BindableProperty.Create(
                                         propertyName: "MyEntry",
                                         returnType: typeof(string),
                                         declaringType: typeof(MyView),
                                         defaultValue: string.Empty,
                                         defaultBindingMode: BindingMode.TwoWay);