Binding after data context is changed

[florin2905]

Hi,

I have a strange problem.

I have a WPF screen on which I have an extended TextBox that makes some conversions in some cases.That property is bound to a property on view model.

When the data context is changed then the conversions are reevaluated. When reevaluated my extended TextBox has the new data context but the BindingOperations.GetBindingExpression(textBox, dpproperty).DataItem is still having the old data context.

Maybe the conversion that I make is too early after changing the data context?

Usually the data context is not changed into the whole screen so the bindings to be reevaluated?

Thanks!

[Sl1ver]

I would put the data into a string. The way im doing it here means that the TextData is updated everytime something changes from either end(front or back).

 private string textData;
        public string TextData
        {
            get { return textData; }
            set
            {
                textData= value;
                OnNotifyPropertyChanged("TextData");
            }
        }

extend your class with

public class YourClassExtended : NotificationBase
{
}

and create that NotificationBase class

using System;
using System.ComponentModel;
using System.Windows;
 
namespace StatsTool.AddIns.Models
{
    public class NotificationBase : INotifyPropertyChanged
    {
        protected void OnNotifyPropertyChanged(string p)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(p));
            }
        }
 
        public bool IsDesignTime
        {
            get
            {
                return (Application.Current == null) || (Application.Current.GetType() == typeof(Application));
            }
        }
 
        #region INotifyPropertyChanged Members
 
        public event PropertyChangedEventHandler PropertyChanged;
 
        #endregion
    }
}

[florin2905]

The bindings are refreshed into the whole tree when data context is changed.

But in my case I have some bindings on the template of my extended TextBox.

Here the DataContext is changed with some delay after the control where is used triggers the DataContext event, so the bindings are refreshed before the DataContext from my extended TextBox template is really changed, so the binding is still pointing to the old DataContext.

[Frinavale]

I've seen this happen in someone else's code before when they were not binding to the correct item.

For example, they were supposed to be binding to the DataContext of the page, but they were actually binding to something like the DataContext of a parent element whose DataContext was the page.

I'm not entirely sure what was happening, but the result was similar: the data context changed but the child element was still holding onto the old object.

After I fixed the bindings, the problem went away.

Your problem might be trickier than the one I fixed a few weeks ago.

-Frinny