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Hi
is that correct to call an element of a view from the viewmodel????
(i'm using MVVMLight)
example:
var grd = (RadGridView)e.Source; (e is KeyEventArgs)
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It is not generally considered good practice for the viewmodel to have any knowledge of the view. generally, when you use the MVVM pattern, you should manipulate the underlying collections, which will be bound to the View in the XAML. You should provide more information as to what you are trying to accomplish, so that someone may help you more specifically.
When I was a coder, we worked on algorithms. Today, we memorize APIs for countless libraries — those libraries have the algorithms - Eric Allman
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Thanks for your help,
Can i use <x:code> in xaml for focusing on elements(like gridview) or getting the current item of a gridview or something like that in MVVM????
example:
viewmodel:
void BnbankPreviewKeyDownCommandExecute(KeyEventArgs p)
{
var grd = (RadGridView)p.Source;
var rowIndex = grd.Items.IndexOf(grd.SelectedItem);
if (((Keyboard.Modifiers != ModifierKeys.Shift) & (p.Key == Key.Tab & grd.CurrentColumn.DisplayIndex == grd.Columns.Count - 1)) || (p.Key == Key.Down))
{
if (rowIndex + 1 == grd.Items.ItemCount)
{
if (p.Key == Key.Tab & grd.CurrentColumn.DisplayIndex == grd.Columns.Count -1)
{
p.Handled = true;
InputSimulator.SimulateKeyDown(VirtualKeyCode.DOWN);
}
grd.CurrentCellInfo = new GridViewCellInfo(grd.Items[rowIndex], grd.Columns[0]);
grd.Focus();
grd.CommitEdit();
SaveBnbankCommandExecute(BnbankSelectedRow);
grd.BeginInsert();
}
}
}
view(Xaml):
<telerik:RadGridView x:Name="RadGridView1" ShowInsertRow="True"
ItemsSource="{Binding AllBnbanks}" SelectedItem="{Binding BnbankSelectedRow, Mode=TwoWay}"
CanUserFreezeColumns="False" AutoGenerateColumns="False" Height="300" CanUserInsertRows="True" ShowGroupPanel="False" FontFamily="Tahoma" FontSize="10" Margin="14,2,16,2">
<i:Interaction.Triggers>
<i:EventTrigger EventName="PreviewKeyDown">
<cmd:EventToCommand Command="{Binding Path=BnbankPreviewKeyDownCommand, Mode=Default,UpdateSourceTrigger=PropertyChanged}" PassEventArgsToCommand="True"/>
</i:EventTrigger>
</i:Interaction.Triggers>
<telerik:RadGridView.Columns>
<telerik:GridViewDataColumn DataType="{x:Null}" UniqueName="Bnba01"/>
<telerik:GridViewDataColumn DataType="{x:Null}" UniqueName="Bnba02"/>
</telerik:RadGridView.Columns>
</telerik:RadGridView>
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The view should always render and style the data. the viewModel is purely for databound business objects, business rules, commands, and collections of items. Focusing would relate to the gridview so it should be part of the view. Current Item, selected item relates to a collection which is the data being bound by the viewmodel thus that logic should be in the viewmodel.
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sorry to ask again,
I want to be sure if is that correct in MVVM architecture to use x:Code in xaml instead of code behind???????
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At best you should try to avoid writing code in your views code-behind. Remember MVVM is all about rendering data through binding. So you should avoid using x:code. You must to see a view as a template for displaying your data. Not for any business logic. leave xaml for xaml. If you want to add specific logic for your view do it in your viewModel rather.
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I am developing a silverlight application.
Project1 is the webhost i.e. wheer the default.aspx page is
Project2 holds the silverlight pages.
Project3 holds the wcf.
I have set the connectionstring to sql server inside Project3 in the web.config
All works fine.
There is a separate project called DataLayer which I currently use inside my .net windows applications to connect to the database, etc. This project has the connectionstring to sql server saved inside the App.config
Question:
In the Project3, where wcf is used, I try to call the separate project I mentioned above to connect to the database. But the error message is The connection has not been initialized.
Any thoughts on how to solve this please?
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Hi could you please supply the code. where you are directly calling the other project. because somewhere you are not initializing or opening the connection or that connectionstring from the app.config is not in your web.config in project 3. And the only way I can diagnose the problem. Is to see what you are doing else it's all based on assumptions on my part.
thanks
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First of all I have a listbox in which I am using a data template to show a stackpanel with a textbox and buttons(one for each day of the week).. The question I have is because these stackpanels are added dynamically to the listbox is there some way that I can know the index of the item in the listbox from which a button is clicked. Using the button click event I don't see a way that I can tell if btnSunday is from row 0 or row 1. Any help would be appreciated thank you.
Humble Programmer
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First of all out the box WPF wraps the listbox control in what is called a CollectionViewSource. This can provide you with information on the currently selectedItem as well as sorting and grouping items.
Get the CurrentItem and on your ObservableCollection of buttons just call IndexOf() and pass in the item. This should give you your index.
for exampe:
In your view xaml on the listbox set
IsSynchronizedWithCurrentItem="True"
then in your viewmodel (just bare inmind my collection is of themes)
public MainViewModel()
{
_theme = new ObservableCollection<Themes>();
_themesView = CollectionViewSource.GetDefaultView(_theme);
_themesView.CurrentChanging += new CurrentChangingEventHandler(_themesView_CurrentChanging);
_themesView.CurrentChanged += new EventHandler(_themesView_CurrentChanged);
}
This allows you to than have access to the current item of the collection.
In the event below you can do whatever you want with the current object. eg; index of your button item that you have selected.
void _themesView_CurrentChanged(object sender, EventArgs e)
{
ListCollectionView view = sender as ListCollectionView;
int index = _theme.IndexOf(view.CurrentItem as Themes);
}
Hope this helps to some extent.
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I have a user control whose data context is a ViewModel. The user control has a listbox bound to an ObservableCollection.
When I have to add a new object to the listbox, I click on the 'Add new' button that opens an Open-file-dialog. After selecting the file from this dialog, I want to do further operations in the ViewModel. What is the best way to call/refer a method of the ViewModel in the user-control code-behind? Please suggest a solution.
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2, no 3, no, actually there are a number of ways to achieve this. Some, Galasofts MVVM Light use a static copy of the Viewmodel, there are also a controller type pattern and you can always pass an instance of the viewmodel around. And I'm confidant there are more solutions than that.
Never underestimate the power of human stupidity
RAH
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Could you please tell us which part of this scenario requires you to refer to the VM in the View? I can see nothing in there that indicates that you need to do this.
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The code-behind of the user-control is handling the 'Add New' button click event because I wanted to work with the Open file dialog (and I thought I could not have openfiledialog in the ViewModel, but now it seems like I can do it with Relaycommand).
After selecting the file from the Open file dialog, I want the further operations to be done in the ViewModel, so here is where I need to refer to the VM from the view.
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The standard way for doing this in an MVVM type application is to have an interface that copes with the OpenFileDialog, and use this.
What I mean by this, is that you have an interface (we'll call it IFileOpenDialog) and that you create a class that implements this interface. Now, this class would simply wrap the call to opening the file dialog, and you would register it with something like a service locator - then your VM retrieves an instance of this class from the service locator using the interface and uses that to open the dialog.
Typically, your command would look something like this:
private void OpenFile(object o)
{
IFileOpenDialog fileOpen = ServiceLocator.Get<IFileOpenDialog>();
fileOpen.Filters = "All files (*.*)|*.*|";
bool? result = fileOpen.ShowDialog();
if (result.HasValue && result.Value == true)
{
myFile = fileOpen.FileName;
}
}I've just knocked this up in the CP editor, so I apologise for any syntax errors, but hopefully this should demonstrate what I've been talking about.
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Pete O'Hanlon wrote: I've just knocked this up in the CP editor
I think that answer requires a pregnant pause before continuing...
WE ARE DYSLEXIC OF BORG. Refutance is systile. Your a$$ will be laminated.
There are 10 kinds of people in the world: People who know binary and people who don't.
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Well, what were you expecting?
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Thank you very much Collin. This solution worked very well for me.
Can you please help me with one more problem? A listbox in the user control is not displaying any data. Here are the details :
The user control (ucPlane) datacontext is set to PlaneListViewModel. The PlaneListViewModel is having
a public property that provides an ObservableCollection of PlaneViewModel objects. This property is called PlaneList.
The listbox itemsource is set as follows :
<ListBox x:Name="lstPlane"
ItemsSource="{Binding Path=PlaneList}"
>
</ListBox>
A Datatemplate defined in the
<UserControl.Resources> section is defined as follows :
<DataTemplate DataType="{x:Type viewModel:PlaneViewModel}">
......
</DataTemplate>
Can you please provide an example or link to an appropriate example that does what I want to do? I searched on the net for a solution but they seem to be too complex for me. I just want to bind a listbox to an ObservableCollection by using 2 view models - PlaneListViewModel and PlaneViewModel.
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Thank you Collin. After digging deep into it, I found the reason why the listbox was not getting populated. The View model had two constructors and that was the root problem. When we have more than one constructor for a class, the INotifyProperty changed does not work correctly. The PropertyChanged event is always equal to null, so it does not notify the listbox when the collection changes.
So when I changed the viewmodel to have only one constructor, it works perfectly.
Thanks once again for your help.
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Hello,
I m in a bit trouble can any one please help me?
I have added a DataGrid on a usercontrol page in silverlight 4.And bind it to an 'xyz' table. When i m updating the contents of the table , m passing the xyzId of selected row which is in hidden column. Now were the problem arises m unable to get the value , it returns empty string . Any help appreciated?
Regards
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You should NOT be working with the visual control when manipulating the data. You should be working with the underlying collection you have bound to the visual control.
Never underestimate the power of human stupidity
RAH
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Hello Holmes,
Thanks for your reply. I have bounded the datagrid Itemsource with service result.
That's the problem. Can you provide an sample or link to know how to get this done?.
Regards
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Hello buddies,
Solved it this way:
clsXYZ _clsxyz= dgxyz.SelectedItem as clsXYZ;
Regards
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Hi,
I want to add an image column to my data grid which is bound to a list. I had tried few options but didn't worked. No error coming but image is not getting loaded. what is the solution.
Thanks
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