Bug 22433 - Binding doing funny thing
Summary: Binding doing funny thing
Alias: None
Product: Forms
Classification: Xamarin
Component: Forms ()
Version: 1.2.2
Hardware: PC Windows
: Normal minor
Target Milestone: ---
Assignee: Bugzilla
Depends on:
Reported: 2014-08-27 19:16 UTC by mgwalm
Modified: 2016-06-13 16:00 UTC (History)
5 users (show)

Tags: AC
Is this bug a regression?: ---
Last known good build:

hellopage.xaml (3.01 KB, application/xaml+xml)
2014-08-27 19:21 UTC, mgwalm
homepage.xaml.cs (3.85 KB, text/plain)
2014-08-27 19:22 UTC, mgwalm

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Description mgwalm 2014-08-27 19:16:31 UTC
I have an issue with binding. Some code follows:
some properties i'm binding to:
    private double _value;

    public double Value
        return _value;
        Debug.WriteLine("Set Value value={0}", value);
        _value = value;
    private string _text;

    public string Text
        return _text;
        Debug.WriteLine("Set Text value={0}", value ?? "");
        _text = value;

the constructor of my page
    public HomePage()

      BindingContext = this;
      Text = "one line";
      Value = 1.1D;
 the xaml in my page:
    <StackLayout Orientation="Vertical" Padding="0" Spacing="0">
      <Label TextColor="Red" Text="Binding Description" HorizontalOptions="Center" />

      <Grid RowSpacing="0" VerticalOptions="FillAndExpand" HorizontalOptions="FillAndExpand">
          <ColumnDefinition Width="100" />
          <ColumnDefinition Width="*" />

          <RowDefinition Height="auto" />
          <RowDefinition Height="auto" />
          <RowDefinition Height="Auto" />
          <RowDefinition Height="*" />

        <Label TextColor="Red" Text="Quoted:" VerticalOptions="Center"/>
        <Entry Text="{Binding Value}" Grid.Column="1" StyleId="Special"
               BackgroundColor="Gray" />

        <Label TextColor="Red" Text="Used:" VerticalOptions="Center" Grid.Row="1"/>
        <Entry Text="{Binding Text, Mode=OneWay}" Grid.Row="1" Grid.Column="1"
               BackgroundColor="Gray" />

        <Label TextColor="Red" Text="Comment:" VerticalOptions="Center" Grid.Row="2" Grid.ColumnSpan="2"/>
        <Editor Text="{Binding Text, Mode=TwoWay}" Grid.Row="3" Grid.ColumnSpan="2"
                VerticalOptions="FillAndExpand" HorizontalOptions="FillAndExpand"

I get this (the debug output) when the constructor executes:

Set Value value=0
Set Text value=one line
Set Value value=1.1
Set Value value=1.1
Set Text value=one line

you'll notice the value is set twice when i'm binding to a double, but set only once when binding to a string.
Comment 1 mgwalm 2014-08-27 19:21:35 UTC
Created attachment 7843 [details]
Comment 2 mgwalm 2014-08-27 19:22:16 UTC
Created attachment 7844 [details]
Comment 3 mgwalm 2014-08-27 19:23:16 UTC
I forgot to say just use the xaml samples downloaded from github and replace the homepage with the attached files.
Comment 4 Arpit Jha 2014-08-28 08:22:00 UTC
I have checked this issue and able to reproduce it.

I have tried following steps to reproduce it.
1.Download XamlSamples from Github.
2.Modify code as above mentioned.
3.Run the application.

I observed that value set twice when  binding to double or Text.

Screencast: http://screencast.com/t/UM5v82iK2

Environment Info: 
Microsoft Visual Studio Professional 2013
Version 12.0.30723.00 Update 3
Comment 5 Rui Marinho 2016-06-13 16:00:15 UTC
Thank you for taking the time to submit this report. After reviewing the description of this bug, we believe it no longer affects the current version of Xamarin.Forms. If you are still experiencing the issue after updating your packages, please reopen this report with an attached reproduction.
For your convenience, we have created some reproduction best practices viewable here: https://gist.github.com/jassmith/92405c300e54a01dcc6d