Binding a custom Entry in Xamarin Forms

Question

I'm trying to extract this Entry in a Frame into a custom element in Xamarin, to get a reusable Entry with border only on top and on bottom:

<Frame xmlns="..."
       HasShadow="False"
       CornerRadius="0"
       Padding="0, 1, 0, 1"
       BackgroundColor="#c0c0c0">
    <Entry Padding="20, 10, 20, 10"
           Placeholder="{Binding Placeholder}"
           Text="{Binding Text}"
           BackgroundColor="#ffffff" />
</Frame>

Code Behind:

public partial class CbSingleEntry : Frame
{
    public static readonly BindableProperty TextProperty = BindableProperty.Create("Text", typeof(string), typeof(CbSingleEntry));
    public static readonly BindableProperty PlaceholderProperty = BindableProperty.Create("Placeholder", typeof(string), typeof(CbSingleEntry));

    public string Text
    {
        get { return (string)GetValue(TextProperty); }
        set { SetValue(TextProperty, value); }
    }

    public string Placeholder
    {
        get { return (string)GetValue(PlaceholderProperty); }
        set { SetValue(PlaceholderProperty, value); }
    }

    public CbSingleEntry()
    {
        InitializeComponent();

        BindingContext = this;
    }
}

When I try to use this custom field, the Placeholder and Text property are correctly set, but I can't bind them to attributes in my class:

// this one works fine
<local:CbSingleEntry Placeholder="Company" Text="My Company" />
// Placeholder works, but Text is always empty
<local:CbSingleEntry Placeholder="Company" Text="{Binding Company}" />

I can confirm that Company has a value, because with a normal text field it works correctly:

// This one works as expected, Text is displayed from binded attribute
<Entry Placeholder="Company" Text="{Binding Company}" />

Lucas Zhang Lucas Zhang · Accepted Answer · 2020-07-14T12:12:43

Cause : in your case , you set the BindingContext in CbSingleEntry

BindingContext = this;

So the binding in ContentPage will not work any more .

Solution:

You could modify the code in CbSingleEntry

in xaml

<Frame 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"
             
             x:Name="CustomView"  // set the name here
       
             x:Class="xxx">
 
       
           <Entry
             
           Placeholder="{Binding Source={x:Reference CustomView},Path=Placeholder}"
           Text="{Binding Source={x:Reference CustomView},Path=Text}"
           BackgroundColor="#ffffff" />
        
    
</Frame>

in code behind

public partial class CbSingleEntry : Frame
{
    public static readonly BindableProperty TextProperty = BindableProperty.Create("Text", typeof(string), typeof(CbSingleEntry));
    public static readonly BindableProperty PlaceholderProperty = BindableProperty.Create("Placeholder", typeof(string), typeof(CbSingleEntry));

    public string Text
    {
        get { return (string)GetValue(TextProperty); }
        set { SetValue(TextProperty, value); }
    }

    public string Placeholder
    {
        get { return (string)GetValue(PlaceholderProperty); }
        set { SetValue(PlaceholderProperty, value); }
    }

    public CbSingleEntry()
    {
        InitializeComponent();

       // BindingContext = this; don't need to set it any more
    }
}

Binding a custom Entry in Xamarin Forms

1 Answers

in xaml

in code behind