Is WPF binding to concurrent collections safe?
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I was wondering, if it is safe to bind a WPF control to a concurrent collection, specifically a wrapper class around one of the System.Collections.Concurrent collections that also implements INotifyCollectionChanged?
I understand that CollectionChanged must be invoked on the UI-thread (and without the index parameters). But, what happens, if another thread manipulates the source collection while the UI is updating itself? Does WPF just gracefully ignore the problem (like it does in so many other places)?
wpf multithreading data-binding concurrent-collections
asked Nov 24 '18 at 23:48
mikemike
459317
add a comment |
I was wondering, if it is safe to bind a WPF control to a concurrent collection, specifically a wrapper class around one of the System.Collections.Concurrent collections that also implements INotifyCollectionChanged?
I understand that CollectionChanged must be invoked on the UI-thread (and without the index parameters). But, what happens, if another thread manipulates the source collection while the UI is updating itself? Does WPF just gracefully ignore the problem (like it does in so many other places)?
wpf multithreading data-binding concurrent-collections
asked Nov 24 '18 at 23:48
mikemike
459317
1
To be absolutely sure, the collection's enumerator must be threadsafe, which is the case in ConcurentBag. Fortunatelly, wpf comes with BindingOperations.EnableCollectionSynchronization, that solves this problem even with ObservableCollection or List. Immutable collections are also an option
– Liero
Nov 25 '18 at 9:02
add a comment |
I was wondering, if it is safe to bind a WPF control to a concurrent collection, specifically a wrapper class around one of the System.Collections.Concurrent collections that also implements INotifyCollectionChanged?
I understand that CollectionChanged must be invoked on the UI-thread (and without the index parameters). But, what happens, if another thread manipulates the source collection while the UI is updating itself? Does WPF just gracefully ignore the problem (like it does in so many other places)?
wpf multithreading data-binding concurrent-collections
asked Nov 24 '18 at 23:48
mikemike
459317
I was wondering, if it is safe to bind a WPF control to a concurrent collection, specifically a wrapper class around one of the System.Collections.Concurrent collections that also implements INotifyCollectionChanged?
I understand that CollectionChanged must be invoked on the UI-thread (and without the index parameters). But, what happens, if another thread manipulates the source collection while the UI is updating itself? Does WPF just gracefully ignore the problem (like it does in so many other places)?
wpf multithreading data-binding concurrent-collections
wpf multithreading data-binding concurrent-collections
asked Nov 24 '18 at 23:48
mikemike
459317
asked Nov 24 '18 at 23:48
mikemike
459317
asked Nov 24 '18 at 23:48
mikemike
459317
asked Nov 24 '18 at 23:48
mikemike
459317
asked Nov 24 '18 at 23:48
mikemike
459317
459317
1
To be absolutely sure, the collection's enumerator must be threadsafe, which is the case in ConcurentBag. Fortunatelly, wpf comes with BindingOperations.EnableCollectionSynchronization, that solves this problem even with ObservableCollection or List. Immutable collections are also an option
– Liero
Nov 25 '18 at 9:02
add a comment |
1
To be absolutely sure, the collection's enumerator must be threadsafe, which is the case in ConcurentBag. Fortunatelly, wpf comes with BindingOperations.EnableCollectionSynchronization, that solves this problem even with ObservableCollection or List. Immutable collections are also an option
– Liero
Nov 25 '18 at 9:02
1
1
To be absolutely sure, the collection's enumerator must be threadsafe, which is the case in ConcurentBag. Fortunatelly, wpf comes with BindingOperations.EnableCollectionSynchronization, that solves this problem even with ObservableCollection or List. Immutable collections are also an option
– Liero
Nov 25 '18 at 9:02
To be absolutely sure, the collection's enumerator must be threadsafe, which is the case in ConcurentBag. Fortunatelly, wpf comes with BindingOperations.EnableCollectionSynchronization, that solves this problem even with ObservableCollection or List. Immutable collections are also an option
– Liero
Nov 25 '18 at 9:02
add a comment |
1 Answer
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That depends on the implementation of your wrapper. Let's make a simple example adding INotifyCollectionChanged to a BlockingCollection<T> allowing calls of non UI threads:
public void AddNotified(T item)
{
base.Add(item);
var args = new NotifyCollectionChangedEventArgs(
NotifyCollectionChangedAction.Add,
item,
Count - 1);
//Ensure no items are changed until the UI is updated
Application.Current.Dispatcher.Invoke(() =>
CollectionChanged?.Invoke(this, args));
}
The implementation of Add itself is threadsafe, but to be sure the UI shows the current items the implementation you need to ensure that there are no other items are changed between adding and updating (See comment in code).
WPF updates the UI based on the NotifyCollectionChangedAction and updated items passed at raising the INotifyCollectionChanged.CollectionChanged. This means the UI relys on this information. The result: An interim collection update leads to an unsynchronized UI until the update was raised or a NotifyCollectionChangedAction.Reset was called and the UI shows different items like inside your source collection.
Synchronizing collections with the UI is a very wide and intresting topic. There are already multiple solutions available that may match your specific problem. To give you some possible approaches to solve problems like this have a look at here are some links:
- Is there a Threadsafe Observable collection in .NET 4?
- Threadsafe ObservableCollection
BindingOperations.EnableCollectionSynchronization
answered Nov 25 '18 at 8:03
FruchtzwergFruchtzwerg
6,603122836
add a comment |
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That depends on the implementation of your wrapper. Let's make a simple example adding INotifyCollectionChanged to a BlockingCollection<T> allowing calls of non UI threads:
public void AddNotified(T item)
{
base.Add(item);
var args = new NotifyCollectionChangedEventArgs(
NotifyCollectionChangedAction.Add,
item,
Count - 1);
//Ensure no items are changed until the UI is updated
Application.Current.Dispatcher.Invoke(() =>
CollectionChanged?.Invoke(this, args));
}
The implementation of Add itself is threadsafe, but to be sure the UI shows the current items the implementation you need to ensure that there are no other items are changed between adding and updating (See comment in code).
WPF updates the UI based on the NotifyCollectionChangedAction and updated items passed at raising the INotifyCollectionChanged.CollectionChanged. This means the UI relys on this information. The result: An interim collection update leads to an unsynchronized UI until the update was raised or a NotifyCollectionChangedAction.Reset was called and the UI shows different items like inside your source collection.
Synchronizing collections with the UI is a very wide and intresting topic. There are already multiple solutions available that may match your specific problem. To give you some possible approaches to solve problems like this have a look at here are some links:
- Is there a Threadsafe Observable collection in .NET 4?
- Threadsafe ObservableCollection
BindingOperations.EnableCollectionSynchronization
answered Nov 25 '18 at 8:03
FruchtzwergFruchtzwerg
6,603122836
add a comment |
That depends on the implementation of your wrapper. Let's make a simple example adding INotifyCollectionChanged to a BlockingCollection<T> allowing calls of non UI threads:
public void AddNotified(T item)
{
base.Add(item);
var args = new NotifyCollectionChangedEventArgs(
NotifyCollectionChangedAction.Add,
item,
Count - 1);
//Ensure no items are changed until the UI is updated
Application.Current.Dispatcher.Invoke(() =>
CollectionChanged?.Invoke(this, args));
}
The implementation of Add itself is threadsafe, but to be sure the UI shows the current items the implementation you need to ensure that there are no other items are changed between adding and updating (See comment in code).
WPF updates the UI based on the NotifyCollectionChangedAction and updated items passed at raising the INotifyCollectionChanged.CollectionChanged. This means the UI relys on this information. The result: An interim collection update leads to an unsynchronized UI until the update was raised or a NotifyCollectionChangedAction.Reset was called and the UI shows different items like inside your source collection.
Synchronizing collections with the UI is a very wide and intresting topic. There are already multiple solutions available that may match your specific problem. To give you some possible approaches to solve problems like this have a look at here are some links:
- Is there a Threadsafe Observable collection in .NET 4?
- Threadsafe ObservableCollection
BindingOperations.EnableCollectionSynchronization
answered Nov 25 '18 at 8:03
FruchtzwergFruchtzwerg
6,603122836
add a comment |
That depends on the implementation of your wrapper. Let's make a simple example adding INotifyCollectionChanged to a BlockingCollection<T> allowing calls of non UI threads:
public void AddNotified(T item)
{
base.Add(item);
var args = new NotifyCollectionChangedEventArgs(
NotifyCollectionChangedAction.Add,
item,
Count - 1);
//Ensure no items are changed until the UI is updated
Application.Current.Dispatcher.Invoke(() =>
CollectionChanged?.Invoke(this, args));
}
The implementation of Add itself is threadsafe, but to be sure the UI shows the current items the implementation you need to ensure that there are no other items are changed between adding and updating (See comment in code).
WPF updates the UI based on the NotifyCollectionChangedAction and updated items passed at raising the INotifyCollectionChanged.CollectionChanged. This means the UI relys on this information. The result: An interim collection update leads to an unsynchronized UI until the update was raised or a NotifyCollectionChangedAction.Reset was called and the UI shows different items like inside your source collection.
Synchronizing collections with the UI is a very wide and intresting topic. There are already multiple solutions available that may match your specific problem. To give you some possible approaches to solve problems like this have a look at here are some links:
- Is there a Threadsafe Observable collection in .NET 4?
- Threadsafe ObservableCollection
BindingOperations.EnableCollectionSynchronization
answered Nov 25 '18 at 8:03
FruchtzwergFruchtzwerg
6,603122836
That depends on the implementation of your wrapper. Let's make a simple example adding INotifyCollectionChanged to a BlockingCollection<T> allowing calls of non UI threads:
public void AddNotified(T item)
{
base.Add(item);
var args = new NotifyCollectionChangedEventArgs(
NotifyCollectionChangedAction.Add,
item,
Count - 1);
//Ensure no items are changed until the UI is updated
Application.Current.Dispatcher.Invoke(() =>
CollectionChanged?.Invoke(this, args));
}
The implementation of Add itself is threadsafe, but to be sure the UI shows the current items the implementation you need to ensure that there are no other items are changed between adding and updating (See comment in code).
WPF updates the UI based on the NotifyCollectionChangedAction and updated items passed at raising the INotifyCollectionChanged.CollectionChanged. This means the UI relys on this information. The result: An interim collection update leads to an unsynchronized UI until the update was raised or a NotifyCollectionChangedAction.Reset was called and the UI shows different items like inside your source collection.
Synchronizing collections with the UI is a very wide and intresting topic. There are already multiple solutions available that may match your specific problem. To give you some possible approaches to solve problems like this have a look at here are some links:
- Is there a Threadsafe Observable collection in .NET 4?
- Threadsafe ObservableCollection
BindingOperations.EnableCollectionSynchronization
answered Nov 25 '18 at 8:03
FruchtzwergFruchtzwerg
6,603122836
answered Nov 25 '18 at 8:03
FruchtzwergFruchtzwerg
6,603122836
answered Nov 25 '18 at 8:03
FruchtzwergFruchtzwerg
6,603122836
answered Nov 25 '18 at 8:03
FruchtzwergFruchtzwerg
6,603122836
6,603122836
add a comment |
add a comment |
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1
To be absolutely sure, the collection's enumerator must be threadsafe, which is the case in ConcurentBag. Fortunatelly, wpf comes with BindingOperations.EnableCollectionSynchronization, that solves this problem even with ObservableCollection or List. Immutable collections are also an option
– Liero
Nov 25 '18 at 9:02