CODEWITHSUNDEEP
c#wpfdependency-properties
Seekeer
Seekeer

Reputation: 1394

Cant use control's dependency property

I have my custom control named "FileSelectDialog" with Dependency Property: 

    public static readonly DependencyProperty FilePathProperty =
         DependencyProperty.Register("FilePath", typeof(string), typeof(FileSelectDialog));

    public string FilePath
    {
        get { return (string)GetValue(FilePathProperty); }
        set { SetValue(FilePathProperty, value); }
    }

Then I'm trying to bind to this dependency property like this:

    <controls:FileSelectDialog FilePath="{Binding FolderName}"/>

But nothing happing, no initial text shown in my control, no updated text's saving to 'FolderName' property! I got such error in Output window:

    System.Windows.Data Error: 40 : BindingExpression path error: 'FolderName' property not found on 'object' ''FileSelectDialog' (Name='FolderSelector')'. BindingExpression:Path=FolderName; DataItem='FileSelectDialog' (Name='FolderSelector'); target element is 'FileSelectDialog' (Name='FolderSelector'); target property is 'FilePath' (type 'String')

So, as far as I understand, control try to find property 'FolderName on itself, while it must look for it in parents control DataContext. For example, when I use simple textbox:

    <TextBox Text="{Binding Path=FolderName}"/>

All is working fine.

Upvotes: 1

Views: 140

Answers (3)

Manish Basantani
Manish Basantani

Reputation: 17499

no initial text shown in my control

I understand you are exposing this property in a custom control, but are you updating some of the control in your customcontrol with the value set in your dependency property?

You may need to attach a callback and show the value set in your DP in some control in your customcontrol.

Like:

public static readonly DependencyProperty FilePathProperty =           DependencyProperty.Register("FilePath", typeof(string), typeof(FileSelectDialog),  new FrameworkPropertyMetadata(false, FrameworkPropertyMetadataOptions.None,HandleFilePathPropertyChanged));

    private static void HandleFilePathPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var control= (FileSelectDialog)d;
        control.SomeUIControl.Text= (string)e.NewValue;
    }

If already doing this, then the second problem is the error shown in Binding. For this try setting the DataContext of your control to the object which has the source property.

    <controls:FileSelectDialog x:Name="customControl" FilePath="{Binding FolderName}"/> 
   ... code-behind.
     customControl.DataContext = sourceObject.

Upvotes: 1

Ankesh
Ankesh

Reputation: 4885

You have to witre the property changed call back function 

   public static readonly DependencyProperty FilePathProperty =
      DependencyProperty.Register("FilePath", typeof(string), 
typeof(FileSelectDialog),new UIPropertyMetadata(
                new PropertyChangedCallback(PropertyChanged))); 


private static void PropertyChanged(DependencyObject d,    
     DependencyPropertyChangedEventArgs e)       
    {           
        //Do your Stuff       
    }

Upvotes: 0

GameAlchemist
GameAlchemist

Reputation: 19294

Seems a basic DataContext issue to me How did you set the DataContext of your FileSelectDialog Control ? seems you set the dataContext in code as 'Me'/'this' or in xaml with 'RelativeSource Self' or something like this.

Upvotes: 3

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