CODEWITHSUNDEEP
wpfdata-bindingmvvminotifypropertychanged
Sergey Bokhantsev
Sergey Bokhantsev

Reputation: 13

application hungs up when INotifyPropertyChanged event calls

I have some strange problem in my WPF app. I'm using a MVVM pattern and this is the part of my MainWindowViewModel:

// GridView control in MainWindow.xaml binded to this property 
public DataTable DT
{
   get { return _dt; }
}

// INotifyPropertyChanged Member for refreshing bindings
public void OnPropertyChanged(string propertyName)
{
   if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}

// my function
void OnCreateTable()
{
   _dt = // creating new table here
    OnPropertyChanged("DT"); // refresh binding
}

When I call OnCreateTable() program almost allways hangs up with 100% CPU usage (sometimes with no CPU usage but others errors like incorrect data in GridView control).

While debugging I discovered some facts:

1) OnCreateTable() and data bindings work fine if make pause before OnPropertyChanged:

void OnCreateTable()
{
   _dt = // creating new table here
   Thread.Sleep(1000); //!!!
   OnPropertyChanged("DT"); // refresh binding
}

2) OnCreateTable() and data bindings work fine if trace it with "step over" (because this makes pause before OnPropertyChanged too)

I can't understand why I need to make pause before OnPropertyChanged.

Upvotes: 0

Views: 184

Answers (2)

Sergey Bokhantsev
Sergey Bokhantsev

Reputation: 13

I think I found the problem. Sorry, I forgot that I have added the property name checking:

public void OnPropertyChanged(string propertyName)
{
   VerifyPropertyName(propertyName);

   if (PropertyChanged != null)
         PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}

[Conditional("DEBUG")]
    public void VerifyPropertyName(string propertyName)
    {
        // Verify that the property name matches a real,  
        // public, instance property on this object.
        if (TypeDescriptor.GetProperties(this)[propertyName] == null)
        {
            throw new Exception("Invalid property!");
        }
    }

I can't understand why, but calling VerifyPropertyName() needs a pause, or it results in that bug, I wrote. If I remove call to VerifyPropertyName() all works propertly!

Upvotes: 0

paparazzo
paparazzo

Reputation: 45096

Try setting the public property. It is kind of a reach but too much for a comment. 

public DataTable DT
{
    get { return _dt; }
    set 
    {
        if(_dt == value) return;
        _dt = value;
        OnPropertyChanged("DT");
    }
}

DT = // creating new table here

Upvotes: 1

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