The WPF / Silverlight Zone

7:25 17 Sep '12

So I have this XAML code:

<Window.Resources>
    <local:MainViewModel x:Key="ViewModel" />
</Window.Resources>

And this is the XAML for the actual control:

            <StackPanel Orientation="Horizontal"  Width="897" Margin="5" DataContext="{StaticResource ViewModel}">         
                <ItemsControl Width="897" ItemsSource="{Binding Intersections}">                   
                    <ItemsControl.ItemTemplate>
                        <DataTemplate>
                            <WrapPanel  Width="897"  >
                                <RadioButton GroupName="Intersections" 
                         Content="{Binding Text}" 
                         IsChecked="{Binding IsChecked, Mode=TwoWay}" Width="150"/>
                           </WrapPanel>                                      
                        </DataTemplate>
                    </ItemsControl.ItemTemplate>
                </ItemsControl>
            </StackPanel>

In the code behind I have this public class:

Public Class MainViewModel
    Sub New()
        Intersections.Add(New Insertion() With {.Text = "Item 1"})
        Intersections.Add(New Insertion() With {.Text = "Item 2", .IsChecked = True})
        Intersections.Add(New Insertion() With {.Text = "Item 3"})
        Intersections.Add(New Insertion() With {.Text = "Item 4"})
    End Sub
    Private _Intersections As New ObjectModel.ObservableCollection(Of Insertion)
    Public Property Intersections() As ObjectModel.ObservableCollection(Of Insertion)
        Get
            Return _Intersections
        End Get
        Set(ByVal value As ObjectModel.ObservableCollection(Of Insertion))
            _Intersections = value
        End Set
    End Property
 
    Public Class Insertion
        Private _Text As String
        Public Property Text() As String
            Get
                Return _Text
            End Get
            Set(ByVal value As String)
                _Text = value
            End Set
        End Property
 
        Private _IsChecked As Boolean
        Public Property IsChecked() As Boolean
            Get
                Return _IsChecked
            End Get
            Set(ByVal value As Boolean)
                _IsChecked = value
            End Set
        End Property
    End Class
End Class

The problem Im haveing is to get the RadioButtons to be shown Horizantaly, and I cant figure out how to do that. I have tried to set IsItemsHost="True" but Its giving me the error

"A panel with IsItemsHost="true" is not nested in an ItemsControl. Panel must be nested in ItemsControl to get and show items."

. Either I heave tried to do this in all the wrong places or Im missing some key information here.

To be clear the code works, but its giving me a stack of the RadioButtons, but I want the side by side like a WrapPanel.

The example is taken from here here[^], and I converted it to VB from C#.

modified 2 days ago.

Abhinav S

7:49 17 Sep '12

Use `ItemsPanelTemplate` and put the radio buttons horizontally inside a stack panel. E.g. <ItemsControl.ItemTemplate> <ItemsPanelTemplate> <StackPanel Orientation='Horizontal' "/> </ItemsPanelTemplate> WP7.5 Apps - XKCD \| Calvin \| SMBC \| Sound Meter \| Speed Dial
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8:04 17 Sep '12

I tried this:

<StackPanel Orientation="Horizontal"  Width="897" Margin="5" DataContext="{StaticResource ViewModel}">         
                <ItemsControl Width="897" ItemsSource="{Binding Intersections}">
                        <ItemsPanelTemplate>
                            <StackPanel Orientation="Horizontal">
                                <RadioButton GroupName="Intersections" 
                         Content="{Binding Text}" 
                         IsChecked="{Binding IsChecked, Mode=TwoWay}" Width="150"/>
                            </StackPanel>
                        </ItemsPanelTemplate>                           
                </ItemsControl>
            </StackPanel>

But this time it wont build properly with ItemsPanelTemplate, I have seen this on the webbefore also, but couldnt get it to work, Can you?

Abhinav S

17:25 17 Sep '12

I think (though Im not sure), one needs to put the tag somewhere. WP7.5 Apps - XKCD \| Calvin \| SMBC \| Sound Meter \| Speed Dial
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20:24 17 Sep '12

ITs working now, but its a strange code, and its well over a page long, so I dont think I'll be pasting it here, unless you are really interested
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WPF Editable ComboxBox Question

9:35 17 Sep '12

Ok Found the answer here[^] . The code that works looked like this:

<StackPanel Orientation="Horizontal"  Width="897" Margin="5" DataContext="{StaticResource ViewModel}">
                <ItemsControl Width="897" ItemsSource="{Binding Intersections}">
                    <ItemsControl.Template>
                        <ControlTemplate>
                            <WrapPanel  Width="{TemplateBinding Width}" Height="{TemplateBinding Height}" 
                    FlowDirection="LeftToRight" IsItemsHost="true">
                            </WrapPanel>
                        </ControlTemplate>
                    </ItemsControl.Template>
                    <ItemsControl.ItemTemplate>
                        <DataTemplate>
                            <WrapPanel  Width="120">
                                <RadioButton GroupName="Intersections" Content="{Binding Text}" IsChecked="{Binding IsChecked, Mode=TwoWay}" Width="150"/>
                            </WrapPanel>
                        </DataTemplate>
                    </ItemsControl.ItemTemplate>
                </ItemsControl>
            </StackPanel>

10:46 14 Sep '12

I have this combobox:

<ComboBox x:Name="cboServerList"
        Grid.Row="0"
        Grid.Column="1"
        Margin="5"
        Height="23"
        IsEditable="True"
        ItemsSource="{Binding Servers}"
        SelectedItem="{Binding SelectedServer}"
        TextSearch.TextPath="ServerName"
        Text="{Binding ServerName}">
<ComboBox.ItemTemplate>
    <DataTemplate>
        <TextBlock Text="{Binding ServerName}"/>
    </DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>

Since it's editable, as soon as I start typing the SelectedServer property's setter fires. How can I set it up so that it doesn't fire until the user presses Enter or tabs out?

Thanks

If it's not broken, fix it until it is

11:17 14 Sep '12

Set the UpdateSourceTrigger of the binding to LostFocus. That won't handle the enter key though. Which is probably ok since the enter key has a different meaning. Dunno why you'd want to do this though. Sounds like an issue with your VM setter being too expensive??
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17:21 15 Sep '12

Thanks for the tip SledgeHammer01 wrote: Dunno why you'd want to do this though. Sounds like an issue with your VM setter being too expensive?? Why would you want the property's get to fire on each keystroke? If it's not broken, fix it until it is
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7:18 16 Sep '12

Kevin Marois wrote:
Why would you want the property's get to fire on each keystroke?

Who cares if you update a string 50 times? What do you think happens with WPF controls? If you scroll down a combo box, you'll get a bunch of updates for each item too.

If you are binding to expensive setters, your design is wrong. In your example, it is perfectly fine to update a string property 50 times, but if that is also triggering 50 database updates, then thats an improper design.

You are trying to solve the wrong problem here I think Smile | :)

8:55 16 Sep '12

SledgeHammer01 wrote:
Who cares if you update a string 50 times?

I care. This is a search field. I don't want the search running after every keystroke. Of course it's bound to a property. How else would you do it?

SledgeHammer01 wrote:
If you are binding to expensive setters, your design is wrong. In your example,
it is perfectly fine to update a string property 50 times, but if that is also
triggering 50 database updates, then thats an improper design

This is exactly what I'm trying to avoid. That's why I don't want the setter to execute until the user presses enter. That's a pretty normal requirement.

If it's not broken, fix it until it is

9:14 16 Sep '12

Ok... I'm confused. There are two ways to do search:

1) a real-time live search (i.e. Google, Internet Explorer, etc)
2) only do the search when the user clicks the OK / search button

For #1, you would do it on every key stroke.

For #2, it depends on how your UI is laid out. Do you have a pop up dialog with an OK button? Or is it something like where you have an edit box in the main window frame?

Irregardless of how you are implementing #2 UI wise, I think you are confusing your property setter with your action trigger. Those should be separate. The "public string SearchText" property should not kick off a search. Since all you should be doing in it is updating the property, its fine to update it 50 times. Then your enter key / ok / search button will send a command to the VM to kick off the search.

The button sending the command portion I'm assuming you already know how to do, for trapping the enter key, all you need to do is use your EventToCommand mapper to map the KeyDown event of the edit box to an ICommand and forward along the eventArgs. In your command handler function, you would simply check if the key pressed was the enter key. All nice and MVVM'y Smile | :)

9:31 16 Sep '12

SledgeHammer01 wrote:
Ok... I'm confused. There are two ways to do search:

1) a real-time
live search (i.e. Google, Internet Explorer, etc)
2) only do the search when
the user clicks the OK / search button

Ok, well that's just your opinion. I can point out mroe than a few UI designs where search happens when the user types, and also where nothing happens until you press enter. Open up Windows Explorer and type something into the search field. Nothing happens until you press enter. There's no button, becuase it's an extra step. Type, then reach for the mouse. Bad design IMHO. For heads down work, press enter to confim/trigger and action.

At any rate, I'll set the UpdateSourceTrigger of the binding to LostFocus.

If it's not broken, fix it until it is

10:15 16 Sep '12

Lol... you just described #1 and #2. #2 is trigger based, I thought it was implied that the trigger could be ANYTHING whether it be a button, the enter key, or you stepping on your cats tail. Silly me. At any rate, I'll let others help you from now on, as you are kind of rude to people who help you for free on thier own time .
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