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I guess people are relucent to publish low-brow MVVM examples in fear of getting shot down in flames.
The way I do it (using Entity Framwork) is the ViewModel provides a SaveCommand which the View binds to. After all, it should be up to the user to determine if the data is saved. So when the user clicks the Save button or other events occur, the command is fired and a method can handle the logic to persist the changes back to model.
In EF it's a one liner myContext.SaveChanges();
In your situation it sounds like you'll need to do a bit more leg work. But the stategy should still work. You need to catch the event in the ViewModel using a command.
"You get that on the big jobs."
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I take option 2 over option 1 'almost always'
I treat my Model object as an object whose job it is to go get the data for the client. Once delivered its job is done, so I don't keep a reference to the Model in my ViewModel (again, 'usually' )
So I rarely Update model objects - as they're going to be persisted back in the DB - I create new objects when required and send them back to be stored.
I must confess to not quite understanding your scenario here - how your report and Parameter objects interract - but assuming you are maintaining the report and/or parameter objects, then I would normally have some sort of Apply method as per your option2.
if you do it this way, then at least you have the option of using the Apply method as frequently or infrequently as you want to - on a timer, every time a parameter type is changed - whatever.
But I don't think there's a 'right' way of doing it - and it depends on your exact requirements.
One of the downsides of option 1 is the ability to revert changes quickly... As you're maintaining a reference to the Model and want to cancel changes, you can just re-set your VM from the Model and you're back!
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How do we change themes dynamically, if themes are stored into a DLL?
Generally, if theme is in form of .xaml file, we write in xaml
<ResourceDictionary Source="Themes/ShinyRed.xaml"/>
And in CS:
ResourceDictionary skin = new ResourceDictionary();
skin.Source = new Uri(@"Themes/ShinyRed.xaml", UriKind.Relative);
Window win = Window.GetWindow(this);
win.Resources.MergedDictionaries.Clear();
win.Resources.MergedDictionaries.Add(skin);
where 'Themes' is folder name and 'ShinyRed.xaml' is theme name.
Now, if theme is in form of DLL file, we write in xaml
<ResourceDictionary Source="/ThemeDll;component/ShinyBlue.xaml"/>
where 'ThemeDll' is the name of DLL, and ShinyBlue.xaml is theme name.
How to get same result at run-time?
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I think you can get the result same way as you do it with normal xaml file
in CS:
ResourceDictionary skin = new ResourceDictionary();
Instead of
skin.Source = new Uri(@"Themes/ShinyRed.xaml", UriKind.Relative);
Use this
skin.Source = new Uri(@"/ThemeDll;component/ShinyBlue.xaml", UriKind.Relative);
Window win = Window.GetWindow(this);
win.Resources.MergedDictionaries.Clear();
win.Resources.MergedDictionaries.Add(skin);
it works fine for me.
I hope i got your question correctly.
Work relieves us from three great evils, boredom, vice, and want.
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Thanks! 
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Well, I have been trying to figure this one out for three days straight and I still haven't come up with a fix.
Basically I am trying to swap out the clicked Ellipse with the only empty spot on the 3x3 checkerboard. 8 of the 9 squares are occupied. I need to find the one spot that is not occupied and I can't seem to do it. Why? Because even though there is an empty spot on the grid at runtime, Javascript refuses to acknowledge this. I used the line: var childrenCount = canvasArray[i].children.count; .. so that's all the canvases. If at runtime there is an empty spot, then how come my code refuses to see it? Or am I not writing the right code? How is the empty spot represented and found at runtime? That's what I want to know.
Here is the pseudocode:
if (squareOnGrid is empty) {
log.write(squareOnGrid + ' is empty');
emptySquare = squareOnGrid;
oldPositionBorder = sender;
oldPositionR = checkerPiece.row;
oldPositionC = checkerPiece.col;
checkerPiece.row = empty.row;
checkerPiece.column = squareOnGrid.column;
oldPositionBorder = null;
}
I want to do this with Javascript (not C#).
I already have this (Javascript):
<br />
function switchPlaces(sender) {<br />
<br />
for (var i = 0; i < canvasArray.length; i++) {<br />
var oldLocationBorderParent = sender;<br />
var oldLocationCanvasParent = oldLocationBorderParent.findName('canvas' + (i + 1));<br />
var oldLocationChild = oldLocationCanvasParent.findName('ellipse' + (i + 1));<br />
<br />
var childrenCount = canvasArray[i].children.count;<br />
log.info(childrenCount);
<br />
if (childrenCount == 0) {<br />
log.info(canvasArray[i] + ' has no children');<br />
var emptySpot = canvasArray[i];<br />
sender['Grid.Row'] = emptySpot['Grid.Row'];<br />
sender['Grid.Column'] = emptySpot['Grid.Column'];<br />
oldLocationCanvasParent.children.remove(oldLocationChild);<br />
}<br />
}<br />
}<br />
Here is my Silverlight code:
<br />
<Grid<br />
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"<br />
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"<br />
Loaded="onLoaded" ShowGridLines="True" Background="CornflowerBlue"><br />
<br />
<Grid.ColumnDefinitions><br />
<ColumnDefinition Width="100"/><br />
<ColumnDefinition Width="100"/><br />
<ColumnDefinition Width="100"/><br />
<ColumnDefinition/><br />
</Grid.ColumnDefinitions><br />
<br />
<Grid.RowDefinitions><br />
<RowDefinition Height="100"/><br />
<RowDefinition Height="100"/><br />
<RowDefinition Height="100"/><br />
</Grid.RowDefinitions><br />
<br />
<Border Grid.Row="0" Grid.Column="0" x:Name="b1" MouseLeftButtonUp="switchPlaces" ><br />
<Canvas x:Name="canvas1"><br />
<Ellipse Width="100" Height="100" x:Name="ellipse1" Fill="Red" Visibility="Visible"/><br />
</Canvas><br />
</Border><br />
<br />
<Border Grid.Column="0" Grid.Row="1" x:Name="b2" MouseLeftButtonUp="switchPlaces" ><br />
<Canvas x:Name="canvas2"><br />
<Ellipse Width="100" Height="100" x:Name="ellipse2" Visibility="Visible"/><br />
</Canvas><br />
</Border><br />
<br />
<Border Grid.Column="0" Grid.Row="2" x:Name="b3" MouseLeftButtonUp="switchPlaces" ><br />
<Canvas x:Name="canvas3"><br />
<Ellipse Width="100" Height="100" x:Name="ellipse3" Visibility="Visible"/><br />
</Canvas><br />
</Border><br />
<br />
<Border Grid.Column="1" Grid.Row="1" x:Name="b4" MouseLeftButtonUp="switchPlaces" ><br />
<Canvas x:Name="canvas4"><br />
<Ellipse Width="100" Height="100" x:Name="ellipse4" Visibility="Visible"/><br />
</Canvas><br />
</Border><br />
<br />
<Border Grid.Column="1" Grid.Row="2" x:Name="b5" MouseLeftButtonUp="switchPlaces" ><br />
<Canvas x:Name="canvas5"><br />
<Ellipse Width="100" Height="100" x:Name="ellipse5" Visibility="Visible"/><br />
</Canvas><br />
</Border><br />
<br />
<Border Grid.Column="2" Grid.Row="0" x:Name="b6" MouseLeftButtonUp="switchPlaces" ><br />
<Canvas x:Name="canvas6"><br />
<Ellipse Width="100" Height="100" x:Name="ellipse6" Visibility="Visible"/><br />
</Canvas><br />
</Border><br />
<br />
<Border Grid.Column="2" Grid.Row="1" x:Name="b7" MouseLeftButtonUp="switchPlaces" ><br />
<Canvas x:Name="canvas7"><br />
<Ellipse Width="100" Height="100" x:Name="ellipse7" Visibility="Visible"/><br />
</Canvas><br />
</Border><br />
<br />
<Border Grid.Column="2" Grid.Row="2" x:Name="b8" MouseLeftButtonUp="switchPlaces" ><br />
<Canvas x:Name="canvas8"><br />
<Ellipse Width="100" Height="100" x:Name="ellipse8" Visibility="Visible"/><br />
</Canvas><br />
</Border><br />
<br />
</Grid><br />
If anyone has any idea how to fix this..
Thank you
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I must be missing something here...
What is this canvas array and how does it relate to the Silverlight Grid?
How does the managed Silverlight code know about the canvas array?
How are you calling javascript from managed code?
Mark Salsbery
Microsoft MVP - Visual C++
![Java | [Coffee]](https://codeproject.global.ssl.fastly.net/script/Forums/Images/coffee.gif)
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Hi,
my question is, how do I sort related items of an entity.
In an invoice editing window, I have one ComboBox displaying all customers:
XAML:
<UserControl.Resources>
<CollectionViewSource x:Key="cvsCustomers"
d:DesignSource="{d:DesignInstance local:Customer, CreateList=True}" />
...
</UserControl.Resources>
<ComboBox ItemsSource="{Binding Source={StaticResource cvsCustomers}}" .../>
Code-behind:
Dim cvsCustomers As System.Windows.Data.CollectionViewSource
cvsCustomers = CType(Me.FindResource("cvsCustomers"), System.Windows.Data.CollectionViewSource)
Dim qryCustomers = _
From c In myEntities.Customers _
Order By c.CustomerCode
Select c
cvsCustomers.Source = qryCustomers
Now I have a 2nd ComboBox displaying all contact persons of the selected customer. This works fine, but the entries in this second ComboBox are unsorted / sorted by ID.
XAML:
<ComboBox ItemsSource="{Binding Path=myInvoice.Customer.Contacts}" .../>;
How do I get the list on the 2nd ComboBox sorted?
King regards,
and thanks in advance for tips/suggestions,
Nico
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Hey,
I've been optimising a piece of software with a very large number of simple controls (~30000), most of whom have their parent panel virtualised at any one time (reducing the number in the visual tree to a few hundred). Running through ANTS profiler, I'm told that 60-70% of CPU-time is taken up by UIElement_CreateAutomationPeerDelegate.Invoke and its child methods. A user interacting with the program for 20 seconds or so [creating an additional ~20 of these controls, deleting a few, and moving a few around the page] results in this method being called 5.4 million times. Putting a counter near this method confirms this when run without debugging/ANTS.
As far as I'm aware, I haven't touched AutomationPeer-related methods, and it is used for Accessibility/COM stuff. Can I turn this 'function' off, or are there ways of reducing how many times it is called?
TIA,
Lee
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At the risk of getting 1'ed, I'd say you are trying to band aid things here. Fix the real issue. You shouldn't need 30,000 controls in a single window .
-- Modified Monday, July 18, 2011 7:04 PM
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Haha, well agreed to an extent. The maximum number of controls 'on' the window at any one time is actually around 200 (and usually only around 40) - the rest are held in memory waiting to be connected to the visual tree when scrolling takes place.
I have tried virtualising these 'properly' so that they are re-used but the overhead for them binding to their data is actually more costly than having them just sit in memory (which I certainly found surprising)
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Hi,
is their any timepicker control available in wpf with vb.net?
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I am looking for a way where a control can be enable when an item from a combo box is selected. Is there a simple way through data binding when a user selects an item from a combo box that it then enables another control to be used?
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One way is to bind IsEnabled on the control(s) to the ComboBox SelectedIndex or SelectedItem property using a value converter[^] on the binding to convert the Selectedxxx value to a bool.
[System.Windows.Data.ValueConversion(typeof(int), typeof(bool))]
public class SelectedIndexToIsEnabledConverter : System.Windows.Data.IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return ((int)value >= 0) ? true : false;
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new System.NotImplementedException();
}
}
<UserControl.Resources >
<local:SelectedIndexToIsEnabledConverter x:Key="SelectedIndexToIsEnabledConverter" />
</UserControl.Resources>
...
Example binding:
IsEnabled="{Binding Path=SelectedIndex,ElementName=comboBox1,Converter={StaticResource SelectedIndexToIsEnabledConverter},Mode=OneWay}"
Mark Salsbery
Microsoft MVP - Visual C++
modified on Friday, July 15, 2011 12:33 PM
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Hello,
Could someone help me out here please.. I have a game algorithm problem: http://oi56.tinypic.com/29x6op0.jpg
Thank you
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Please post on the algorithm board[^] if you want algorithms.
Mark Salsbery
Microsoft MVP - Visual C++
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Wrong forum.
Too much of heaven can bring you underground
Heaven can always turn around
Too much of heaven, our life is all hell bound
Heaven, the kill that makes no sound
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Not wrong forum. The people from the algorithm forum sent me here.
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And yet you say you have a problem with an algorithm, ergo it's an algorithm forum post.
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A game algorithm in a Silverlight app.
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Hello All,
I have issue with WCF ASYNC call. WCF service give me a random response. Sometimes it gives me result and sometimes not. I have set max values for binding related properties.
Can anyone can help me to figure out this issue?
Thanks
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This could be something to do with the timeout or buffer size.
Try changing these settings.
Too much of heaven can bring you underground
Heaven can always turn around
Too much of heaven, our life is all hell bound
Heaven, the kill that makes no sound
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Hi,
I wouold like to learn a little about how to design better UI in silverlight or WPF in visual studio.
1-
Is there a book to teach me that in visual studio xaml or should I buy a step by step book in expressin blend? I say expression blend because it seems that I can use the code in expression blend and paste the xaml into visual studio.
Thank you
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