Custom usercontrol binding problem

01-12-2009 6:37 AM |

Hello,

I'm a silverlight newbie, I 've created the following simple "reusable" textbox control. I want to use my control on several pages. I want to be able to bind from my page the Text property of the TextBox inside my control. I added a "Text" property on my control therefore.

MY REUSABLE CONTROL:

<UserControl x:Class="SilverlightApplication1.Controls.MyTextBox"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    xmlns:Controls="clr-namespace:SilverlightApplication1.Controls" 
    >
    <Grid x:Name="LayoutRoot" Background="White">
        <StackPanel Orientation="Horizontal">
            <TextBox x:Name="txtTextBox"></TextBox>
            <TextBlock x:Name="label">This is a test</TextBlock>
        </StackPanel>
    </Grid>
</UserControl>

Code-Behind:

In the code behind of my control I have added the following property:

public string Text
{
     get { return txtTextBox.Text; }
     set { txtTextBox.Text = value; }
}

MY PAGE LOOK LIKE THIS:

<UserControl x:Class="SilverlightApplication1.Page"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
    xmlns:controls="clr-namespace:SilverlightApplication1.Controls"
    Width="400" Height="300"
    Loaded="UserControl_Loaded">
    <Grid x:Name="LayoutRoot" Background="White">
        <controls:MyTextBox Text="{Binding MyText}"></controls:MyTextBox>
    </Grid>
</UserControl>

Code-behind of the Page:

         private void UserControl_Loaded(object sender, RoutedEventArgs e)
        {
            TestClass t = new TestClass();
            t.MyText = "Helllooo!";

            this.DataContext = t;
        } 

When I run this code, Silverlight throws an exception in the InitializeComponent of the Page class, even before the Loaded method is called.

System.Windows.Markup.XamlParseException
AG_E_PARSER_BAD_PROPERTY_VALUE [Line: 8 Position: 35] 

Line 8 is the line where is this line : "<controls:MyTextBox Text="{Binding MyText}"></controls:MyTextBox>" 

When I change line 8 to this :  "<controls:MyTextBox Text="hello"></controls:MyTextBox>"
it works perfeclty ? 

Any one an idea ? 

Re: Custom usercontrol binding problem

01-12-2009 6:44 AM |

Hi,

what's the definition of your TestClass? Is "MyText" defined as a public property?

Re: Custom usercontrol binding problem

01-12-2009 7:00 AM |

Yes, it is.

public class TestClass : INotifyPropertyChanged
    {
        private string _myText;

        public string MyText
        {
            get { return _myText; }
            set 
            { 
                _myText = value;
                OnPropertyChanged("MyText");
            }
        }

        protected virtual void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
    }

Re: Re: Custom usercontrol binding problem

01-12-2009 7:28 AM |

The "Text" property of your user control must be defined as a dependency property if you want to set it in XAML.

Re: Custom usercontrol binding problem

01-12-2009 7:40 AM |

The Issue with you is that your property of your control is simple property

but databinding can be applied to only dependency properties

you can implement your property in the userControl like

public static readonly DependencyProperty TextProperty =  DependencyProperty.Register("Text",typeof(string),typeof(this),null);

Re: Re: Custom usercontrol binding problem

01-12-2009 8:53 AM |

 It works, thank you !