int[] arr = int[100];
listBox1.DataSource = arr;
void ComboBox1SelectedIndexChanged(object sender, EventArgs e)
{
.....//some processes
listBox1.DataSource = null;
listBox1.DataSource = arr;
}
is not working,
also,
listBox1.Refresh(); is not working,
also,
listBox1.Update(); is not working,
i know i can use BindingList<T> but i have to work with only array.
can you help me how can i refresh listbox?
my first answer on stack exchange here.
C# .Net 4.0:
listBox1.DataSource = null;
listBox1.DataSource = names;
I noticed that setting the datasource for the first time, it refreshes.
When it's set, and you try set it to the same one again, it doesn't update.
So I made it null, set it to the same one, and it displayed correctly for me with this issue.
ListBox only updates its shown content when the object that is binded on dataSource notifys it own changes. the BindingSource object has an event called DataSourceChanged. when the Source is changed to a different object the Listbox will update itself.
Same thing when you bind a List. Nothing will happen if you change the List, because the List doesn't notify that it has been changed. There is a Simple solution for this Problem: use BindingList
http://msdn.microsoft.com/de-de/library/ms132679%28v=vs.110%29.aspx
the BindingList has the ListChanged Event is called every time when the List is changed (obviously). So the DataBindings of Windows.Form objects use events like ListChanged to update themselves. A simple List doesn't support this event.
SO if you want to work with a lot of Data Bindings you should know about:
http://msdn.microsoft.com/de-de/library/system.componentmodel.inotifypropertychanged%28v=vs.110%29.aspx
Managed to do just with
FirstListBox.DataContext = null;
FirstListBox.DataContext = App.ViewModel;
Simply loses link and get all the data back to it.
I inherited ListBox and added a public method calling RefreshItems() which does what we want. Already implemented and all. I dont know why they didnt put in a public method.
The problem might come from the ListBox SelectionMode.
For a reason that I don't know, the databinding does not work when SelectionMode is SelectionMode.None.
A workaround could be:
listBox.SelectionMode = SelectionMode.MultiExtended;
listBox.DataSource = myDatasource;
listBox.SelectionMode = SelectionMode.None;
Hope it helps.
well, without binding I only managed with:
this.Hide();
this.Show();
it redraws everything...
try the following
listBox1.DataBind()
Use BeginUpdate and EndUpdate, that should solve it.
No need to set the data source twice
listBox1.BeginUpdate();
listBox1.DataSource = myList;
listBox1.EndUpdate();
Windows forms to see changes especially on Listbox and other controls before load is finished is tricky.
To see data as its loaded use invalidate(); then Update();
Quick Answer
BindingSource bs = new BindingSource();
bs.DataSource = arr;
listbox1.DataSource = bs;
arr[0] = 100; //Do some value change
bs.ResetBindings(false); //Refresh the listbox
Explanation
As stated by Microsoft:
The BindingSource component serves two purposes. First, it provides a layer of indirection when binding the controls on a form to data. This is accomplished by binding the BindingSource component to your data source, and then binding the controls on your form to the BindingSource component. All further interaction with the data, including navigating, sorting, filtering, and updating, is accomplished with calls to the BindingSource component.
So, if you have multiple Controls binded with same data which changes frequently, it is suggested to use BindingSource rather than setting DataSource property of the Controls directly to an Array or List etc.
Moreover, with decompiling ListBox class which is inherited from ListControl in .net 4.6.2, the setter of property DataSource is:
if ((value != null) && (!(value is IList) && !(value is IListSource)))
{
throw new ArgumentException(System.Windows.Forms.SR.GetString("BadDataSourceForComplexBinding"));
}
if (this.dataSource != value)
{
try
{
this.SetDataConnection(value, this.displayMember, false);
}
catch
{
this.DisplayMember = "";
}
if (value == null)
{
this.DisplayMember = "";
}
}
We can see if the value is null the DisplayMember property will automaticly be set to empty. And when you reset a value, several initialization will be performed in SetDataConnection method which takes extra cost.
In contrast, calling BingdingSource.ResetBindings only fires an event:
public void ResetBindings(bool metadataChanged)
{
if (metadataChanged)
{
this.OnListChanged(new ListChangedEventArgs(ListChangedType.PropertyDescriptorChanged, null));
}
this.OnListChanged(new ListChangedEventArgs(ListChangedType.Reset, -1));
}
Although I didn't find the handler in ListBox but I guess there should be less side effects. So I think the highest voted answer is not the best solution.
Related
Could someone help me, how can I update ObservableCollection, which is binded to ListView ItemSource, without blinking? When I do:
Contacs = _contacs;
the whole ListView is blinking. I would like to search in ListView too, but always after replacing the old results with new one, the listview blinks.
The problem here is, that you are reassigning the whole collection. This does not take advantage of the observability and forces the ListView to reload all items. Try to remove/add the items instead so the ListView only needs to update the Items that actually changed.
In the case of searching hiding the unmatched results might be a viable solution too. To do that create a property on your Contact type (called "IsVisible" for example) and bind it to the ListViewItems Visibility Property. (You might need the build in BooleanToVisibility Converter here)
Update
As pointed out in the comments using a CollectionViewSource is the correct wpf way of implementing a search filter. See this answer for details on how to use it.
If you want to enable filtering in your collection then there is no actual need to perform operations directly on your collection.
Use ICollectionView and CollectionViewSource for this purpose.
As you have an ObservableCollection so you can do something like this.
ICollectionView contactsView;
public ICollectionView ContactsView
{
get { return contactsView; }
set
{
if(contactsView != value)
{
contactsView = value;
}
}
}
And in the setter of the ObservableCollection
public ObservableCollection<ContactType> Contacs
{
get { return _contacs; }
set
{
if(_contacs != value)
{
_contacs = value;
ContactsView = CollectionViewSource.GetDefaultView(value);
ContactsView.Filter = ContactsFilter;
}
}
}
where ContactsFilter is a function with following definition.
bool ContactsFilter(object item)
{
var contact = item as ContactType;
if(condition)
return true; //show this item in ListView.
return false; //Do not show this item in ListView
}
and whenever you want to filter items you can do that just by
ContactsView.Refresh();
which I think will be in the TextChanged Event of your text box in which you are entering search query.
More detailed article is at CollectionViewSource
I am using a ListView control to display some lines of data. There is a background task which receives external updates to the content of the list. The newly received data may contain less, more or the same number of items and also the items itself may have changed.
The ListView.ItemsSource is bound to an OberservableCollection (_itemList) so that changes to _itemList should be visible also in the ListView.
_itemList = new ObservableCollection<PmemCombItem>();
_itemList.CollectionChanged += new NotifyCollectionChangedEventHandler(OnCollectionChanged);
L_PmemCombList.ItemsSource = _itemList;
In order to avoid refreshing the complete ListView I do a simple comparison of the newly retrieved list with the current _itemList, change items which are not the same and add/remove items if necessary. The collection "newList" contains newly created objects, so replacing an item in _itemList is correctly sending a "Refresh" notification (which I can log by using the event handler OnCollectionChanged of the ObservableCollection`)
Action action = () =>
{
for (int i = 0; i < newList.Count; i++)
{
// item exists in old list -> replace if changed
if (i < _itemList.Count)
{
if (!_itemList[i].SameDataAs(newList[i]))
_itemList[i] = newList[i];
}
// new list contains more items -> add items
else
_itemList.Add(newList[i]);
}
// new list contains less items -> remove items
for (int i = _itemList.Count - 1; i >= newList.Count; i--)
_itemList.RemoveAt(i);
};
Dispatcher.BeginInvoke(DispatcherPriority.Background, action);
My problem is that if many items are changed in this loop, the ListView is NOT refreshing and the data on screen stay as they are...and this I don't understand.
Even a simpler version like this (exchanging ALL elements)
List<PmemCombItem> newList = new List<PmemCombItem>();
foreach (PmemViewItem comb in combList)
newList.Add(new PmemCombItem(comb));
if (_itemList.Count == newList.Count)
for (int i = 0; i < newList.Count; i++)
_itemList[i] = newList[i];
else
{
_itemList.Clear();
foreach (PmemCombItem item in newList)
_itemList.Add(item);
}
is not working properly
Any clue on this?
UPDATE
If I call the following code manually after updating all elements, everything works fine
OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
But of course this causes the UI to update everything which I still want to avoid.
After a change, you can use the following to refresh the Listview, it's more easy
listView.Items.Refresh();
This is what I had to do to get it to work.
MyListView.ItemsSource = null;
MyListView.ItemsSource = MyDataSource;
I know that's an old question, but I just stumbled upon this issue. I didn't really want to use the null assignation trick or the refresh for just a field that was updated.
So, after looking at MSDN, I found this article:
https://learn.microsoft.com/en-us/dotnet/api/system.componentmodel.inotifypropertychanged?redirectedfrom=MSDN&view=netframework-4.7.2
To summarize, you just need the item to implement this interface and it will automatically detect that this object can be observed.
public class MyItem : INotifyPropertyChanged
{
private string status;
public string Status
{
get => status;
set
{
OnPropertyChanged(nameof(Status));
status = value;
}
}
public event PropertyChangedEventHandler PropertyChanged;
[NotifyPropertyChangedInvocator]
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
So, the event will be called everytime someone changes the Status. And, in your case, the listview will add a handler automatically on the PropertyChanged event.
This doesn't really handle the issue in your case (add/remove).
But for that, I would suggest that you have a look at BindingList<T>
https://learn.microsoft.com/en-us/dotnet/api/system.componentmodel.bindinglist-1?view=netframework-4.7.2
Using the same pattern, your listview will be updated properly without using any tricks.
You should not reset ItemsSource of ListView each time observable collection changed. Just set proper binding that will do your trick. In xaml:
<ListView ItemsSource='{Binding ItemsCollection}'
...
</ListView>
And in code-behind (suggest to use MVVM) property that will be responsible for holding _itemList:
public ObservableCollection<PmemCombItem> ItemsCollection
{
get
{
if (_itemList == null)
{
_itemList = new ObservableCollection<PmemCombItem>();
}
return _itemList;
}
}
UPDATE:
There is similar post which most probably will Answer your question: How do I update an ObservableCollection via a worker thread?
I found a way to do it. It is not really that great but it works.
YourList.ItemsSource = null;
// Update the List containing your elements (lets call it x)
YourList.ItemsSource = x;
this should refresh your ListView (it works for my UAP :) )
An alternative on Xopher's answer.
MyListView.ItemsSource = MyDataSource.ToList();
This refreshes the Listview because it's a other list.
Please check this answer:
Passing ListView Items to Commands using Prism Library
List view Items needs to notify about changes (done is setter)
public ObservableCollection<Model.Step> Steps
{
get { return _steps; }
set { SetProperty(ref _steps, value); }
}
and UpdateSourceTrigger need to be set in xaml
<Image Source="{Binding ImageData, UpdateSourceTrigger=PropertyChanged}" />
I am using a datasource to populate my datagridview with the data. However, im trying to find a way for the user to be able to hide columns that he does not want to see.
I am able to hide and show columns before the program runs using:
[Browsable(false)]
public string URL
{
get
{
return this._URL;
}
set
{
this._URL = value;
this.RaisePropertyChnaged("URL");
}
}
I cannot seem to figure out how to change the [Browsable(false)] at run time.
Any ideas how I could accomplish this?
Basically, I want to bind an "on/off" to a menu.
Apologies if im not using the right terminology when explaining my problem, I am self taught and started a few weeks ago - so still very newbie :)
Edit:
Cant hide the column because when i run my update function all columns appear again. Here is my function for updating:
private void UpdateResults()
{
Invoke(new MethodInvoker(
delegate
{
this.dgvResults.SuspendLayout();
this.dgvResults.DataSource = null;
this.dgvResults.DataSource = this._mySource;
this.dgvResults.ResumeLayout();
this.dgvResults.Refresh();
}
));
}
At run time, you can just specify the column as being invisible:
dgv.Columns["ColumnName"].Visible = false;
The way to do this properly at runtime is to provide a custom ITypedList implementation on the collection, or provide a TypeDescriptionProvider for the type, or (for single-object bindings, not lists), to implement ICustomTypeDescriptor. Additionally, you would need to provide your own filtered PropertyDescriptor implementation. Is it really worth it? In most cases: no. It is much easier to configure the grid properly, showing (or not) the appropriate columns by simply choosing which to add.
Indeed, as others had mention the purpose of BrowsableAttribute is different, but I understand what you want to do:
Let's suppose that we want to create a UserControl than wraps a DataGridView and gives the user the ability to select which columns to display, allowing for complete runtime binding. A simple design would be like this (I'm using a ToolStrip, but you can always use a MenuStrip if that's what you want):
private void BindingSource_ListChanged(object sender, ListChangedEventArgs e) {
this.countLabel.Text = string.Format("Count={0}", this.bindingSource.Count);
this.columnsToolStripButton.DropDownItems.Clear();
this.columnsToolStripButton.DropDownItems.AddRange(
(from c in this.dataGrid.Columns.Cast<DataGridViewColumn>()
select new Func<ToolStripMenuItem, ToolStripMenuItem>(
i => {
i.CheckedChanged += (o1, e2) => this.dataGrid.Columns[i.Text].Visible = i.Checked;
return i;
})(
new ToolStripMenuItem {
Checked = true,
CheckOnClick = true,
Text = c.HeaderText
})).ToArray());
}
In this case, bindingSource is the intermediary DataSource of the dataGrid instance, and I'm responding to changes in bindingSource.ListChanged.
I have a datagrid in my wpf application and I have a simple problem. I have a generic list and I want to bind this collection to my datagrid data source every time an object is being added to the collection. and I'm not interested to use observable collection.
the point is I'm using the same method somewhere else and that works fine. but this time when i press Add button an object is added and datagrid updates correctly but from the second item added to collection datagrid does not update anymore.
Here is the Code :
private void btnAddItem_Click(object sender, RoutedEventArgs e)
{
OrderDetailObjects.Add(new OrderDetailObject
{
Price = currentitem.Price.Value,
Quantity = int.Parse(txtQuantity.Text),
Title = currentitem.DisplayName,
TotalPrice = currentitem.Price.Value * int.Parse(txtQuantity.Text)
});
dgOrderDetail.ItemsSource = OrderDetailObjects;
dgOrderDetail.UpdateLayout();
}
any idea ?
The ItemsSource is always the same, a reference to your collection, no change, no update. You could null it out before:
dgOrderDetail.ItemsSource = null;
dgOrderDetail.ItemsSource = OrderDetailObjects;
Alternatively you could also just refresh the Items:
dgOrderDetail.ItemsSource = OrderDetailObjects; //Preferably do this somewhere else, not in the add method.
dgOrderDetail.Items.Refresh();
I do not think you actually want to call UpdateLayout there...
(Refusing to use an ObservableCollection is not quite a good idea)
I also found that just doing
dgOrderDetails.Items.Refresh();
would also accomplish the same behavior.
If you bind the ItemSource to a filtered list with for example Lambda its not updated.
Use ICollectionView to solve this problem (Comment dont work):
//WindowMain.tvTemplateSolutions.ItemsSource = this.Context.Solutions.Local.Where(obj=>obj.IsTemplate); // templates
ICollectionView viewTemplateSolution = CollectionViewSource.GetDefaultView(this.Context.Solutions.Local);
viewTemplateSolution.SortDescriptions.Clear();
viewTemplateSolution.SortDescriptions.Add(new SortDescription("Name", ListSortDirection.Ascending));
viewTemplateSolution.Filter = obj =>
{
Solution solution = (Solution) obj;
return solution.IsTemplate;
};
WindowMain.tvTemplateSolutions.ItemsSource = viewTemplateSolution;
i use ObservableCollection as my items collection and than in the view model
call CollectionViewSource.GetDefaultView(my_collection).Refresh();
Goal:
Once clicking on add or delete button, the datagridview should be refreshed with the latest data from document.
Problem:
The datagridview can't be refreshed
after making changes by deleting or
adding new data.
I'm using binding source that is linked with datagridview's datasource.
I tried everything with different solution and read advise from different forum but still I can't solve this problem.
I also tried using these syntax "BindingSource.ResetBindings(false)", "BindingSource.Refresh()" etc but no result.
Links below:
How to refresh a bindingsource
http://www.eggheadcafe.com/community/aspnet/2/10114324/datagridview-refresh-from-another-form.aspx
http://blogs.msdn.com/b/dchandnani/archive/2005/03/15/396387.aspx
http://bytes.com/topic/c-sharp/answers/812061-problem-refresh-datagridview
bSrcStock.DataSource = myProductrepository.GetAllProductList();
dgridStock.DataSource = null;
dgridStock.DataSource = bSrcStock;
bSrcStock.ResetBindings(true);
dgridStock.Columns[0].Width = 101;
dgridStock.Columns[1].Width = 65;
dgridStock.Columns[2].Width = 80;
dgridStock.Columns[3].Width = 120;
dgridStock.Columns[4].Width = 90;
I have faced this same issue and found out that the problem is with the initialization of the BindingSource inside a static constructor (The class was a singleton). Upon realizing this, I moved the code to the calling event and it finally worked without needing to assign null or call the clear method. Hope this helps.
No need to define the columns (unless you really want to...)
Then just call for the refreshDataGridView Method every time you add or remove something from your list...
public List<CustomItem> ciList = new List<CustomItem>();
CustomItem tempItem = new CustomItem();
tempItem.Name = "Test Name";
ciList.add(tempItem);
refreshDataGridView();
private void refreshDataGridView()
{
dataGridView1.DataSource = typeof(List<>);
dataGridView1.DataSource = ciList;
dataGridView1.AutoResizeColumns();
dataGridView1.Refresh();
}
You need a list that will inform the BindingSource when an item is added etc. Use a System.ComponentModel.BindingList for that.
Dim lisItems As New System.ComponentModel.BindingList(Of myObject)
Works Great! Only AddRange is missing so this takes care of that:
Private Sub AddRange(ByVal lis As List(Of myObject))
For Each itm In lis
lisItems.Add(itm)
Next
End Sub
https://learn.microsoft.com/en-us/dotnet/api/system.componentmodel.bindinglist-1?view=netframework-4.7.2