Re: Using DataTemplates Trigger for listbox - WPF Discussion Boards

Using DataTemplates Trigger for listbox

18-Dec-15 7:24

I don't use DTOs, I use collection properties of the view model, and make the child objects have the structure of the data I want to get to. Then I can just either iterate through the children for a list, or select using linq the child I need and use the properties of the child object

ChildObjectClass instance=ViewModelName.ChildObjectCollection.Where(c=>Someproperty==MatchThis Value).FirstOrDefault<ChildObjectClass>();

And in the HTML:

<p>Here is the value of my property: @instance.Property</p>

Saurabh18cs17-Dec-15 21:35

17-Dec-15 21:35

Hello Everyone,

I am having a listbox control in my app which is also having datatemplate inside and everything is fine until here. My problem starts when i want to change border background color on different databind for tag property of checkbox [please see datatemplate trigger in below code to understand what i am trying to achieve]. Please help me out.

Comment part in below code are the options i am trying to use but unfortunately not workking

<ListBox Name="listBoxDraftVersions" Height="200" Width="250" Margin="3" ItemsSource="{Binding DraftList}" SelectionMode="Multiple" SelectionChanged="listBoxDraftVersions_SelectionChanged">
<ListBox.ItemTemplate>
<DataTemplate>
<Border x:Name="TheBorder" BorderBrush="Gray" BorderThickness="1" Padding="4" CornerRadius="4" Margin="2">
<CheckBox Name="radioButZone" Content="{Binding DraftName}" Tag="{Binding FunctionCode}" IsChecked="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ListBoxItem}}, Path=IsSelected}">
</CheckBox>
<Border.Background>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="AliceBlue" Offset="0.15" />
<GradientStop Color="White" Offset="0.85" />
<GradientStop Color="Lavender" Offset="1" />
</LinearGradientBrush>
</Border.Background>

</Border>

</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>

Joseph M. Morgan18-Dec-15 7:27

18-Dec-15 7:27

It looks as if you aren't specifying the trigger correctly. It has a value to look for, but it doesn't know of what it is the value. Perhaps if you give it the ElementName and Property as well as the value, then it can know where to look for the situation in which to fire the trigger.

Joey
Joseph M. Morgan
Lairhaven Enterprises
Waynesboro, Virginia, USA

Saurabh18cs20-Dec-15 21:49

20-Dec-15 21:49

Hi Joseph,

Thanks for your prompt response but i am unable to understand what are you trying to say!! Sorry i am bit new in WPF

Can you please help me in fixing this code as i have already shared code in my last post. What exactly has to be done??

Regards

Joseph M. Morgan21-Dec-15 2:19

21-Dec-15 2:19

Saurabh18cs wrote:
Sorry i am bit new in WPF

So am I, unfortunately. What I understand about a trigger is that it has to know three things: What condition fires it, what the source of that condition is, and what to do when it fires.
From my understanding of your code, you are setting the first and the third but not the second. Where you have

XML

<Trigger Property="" Value="CMDSDMODIFYFEATURES">

I think you need to set that property, so it knows where to look for the value "CMDSDMODIFYFEATURES" on that property.
I hope that is clearer--I am going by a very new understanding of WPF.
Joey

Saurabh18cs21-Dec-15 15:28

21-Dec-15 15:28

Hi Joey,

Thanks for this explanation , so in my case this is what i am doing :



My Doubts here??

1) Is datatemplate triggers is correct place to accomplish my work? or some other way like i tried border.style triggers??
2) If datatemplate trigger is a correct way then as per your definition of triggers
Binding="{Binding Tag}" --> This is source
Value="CMDSDMODIFYFEATURES" --> fire if value matches CMDSDMODIFYFEATURES
<Setter TargetName="TheBorder" Property="Background" Value="Blue" /> --> do this stuff

I can see all 3 conditions are meeting here , so please correct me if i am missing something or what is the correct way to do this..

Note:: my checkbox is holding these values i.e. CMDSDMODIFYFEATURES under tag property Tag="{Binding FunctionCode}"

Regards
Saurabh

Joseph M. Morgan30-Dec-15 6:00

30-Dec-15 6:00

Here is an example from "WPF Succinctly" which is a free e-book from Syncfusion.
(I am not connected to them, so I am putting their library link here for everyone.)

XML

<Trigger Property="IsPressed" Value="True">
	<Setter TargetName="Border" Property="Background" Value="Purple" /> 
	<Setter TargetName="Border" Property="BorderBrush" Value="DarkKhaki" /> 
</Trigger

According to the book, the data template or control template is the place to put the triggers.
Note that the property IsPressed is the property to be evaluated. In your case, it is the value of the check box, if I recall correctly. The Value property is the value you want that target property to have in order to fire the trigger. Without knowing your data structures, I am not sue what the binding is doing in your example. I am also not sure why you are using a tag instead of the value of the checkbox. If you use the template for the checkbox control, and the value of "true" is what you want to trigger the modifications, then you should be using this data template for the checkbox and use "True" on the Value property, I would think.
If I am wrong and you are selecting from multiple items as in a radio button group, then you would need to evaluate the value of the group and the trigger would be set on that.

Mind you, I am very new to WPF as well, so this is just my take on what the experts have written. I recommend both this book and some of the tutorials on line through Packtpub and Safari Online, if you have subscriptions to either.

Joseph M. Morgan ("Joey")
Lairhaven Enterprises/Solstice Systems
Waynesboro, Virginia, USA

Saurabh18cs30-Dec-15 15:47

30-Dec-15 15:47

Hi Joseph,

Thanks again for your response.

As a answer of your question, i am using tag property of checkbox because content property is already taken by another another binding property which i want to show on my checkbox. I want to fire trigger based on the tag property of checkbox because i have binded tag property to second property of binding.

<DataTemplate.Triggers>
<DataTrigger Binding="{Binding FunctionCode}" Value="CMDSDMODIFYFEATURES">
<Setter TargetName="TheBorder" Property="Background" Value="{StaticResource MenuBackground}" />
</DataTrigger>
</DataTemplate.Triggers>

as per your post i have to use any property of datatemplate to fire, but what would be that property in my case? I am only passing binding and value as of now to my datatemplate.trigger

Wish you a very happy new year

Saurabh18cs22-Dec-15 22:14

22-Dec-15 22:14

Please help .. i am still not able to find way out

Pete O'Hanlon22-Dec-15 22:31

Pete O'Hanlon

22-Dec-15 22:31

You're attempting to bind to a property that doesn't exist. Your Tag property is actually a property of the CheckBox which is, itself, bound to a different property on your ViewModel. So, you need to set your Trigger to use the underlying property. In other words, replace Binding="{Binding Tag}" with Binding="{Binding FunctionCode}". If you'd checked your Output window when debugging your application, you'd probably have seen a binding error telling you that this was missing.

This space for rent

Saurabh18cs22-Dec-15 23:44

22-Dec-15 23:44

Hi Pete,

Thanks for your response!!

Actually , both ways xaml is not throwing error and neither working. As per your suggestion i have changed trigger i.e.

<DataTemplate.Triggers>
<DataTrigger Binding="{Binding FunctionCode}" Value="CMDSDMODIFYFEATURES">
<Setter TargetName="TheBorder" Property="Background" Value="Blue" />
</DataTrigger>
</DataTemplate.Triggers>

Even after this change background color is not getting changed for checkbox holding tag value "CMDSDMODIFYFEATURES". Am i setting up a setter in correct way?

Regards

Saurabh18cs4-Jan-16 19:28

4-Jan-16 19:28

Someone please help me out achieving this ...

Regards
Saurabh

Saurabh18cs4-Jan-16 22:15

Create Simple WPF datagrid

4-Jan-16 22:15

Hello Everyone,

I found the answer myself, here is how to achieve this :

<DataTemplate.Triggers>
<Trigger SourceName="radioButZone" Property="Tag" Value="CMDDSDMODIFYFEATURES">
<Setter Property="BorderBrush" Value="Orange" TargetName="TheBorder"/>
</Trigger>
</DataTemplate.Triggers>

Thanks everyone for your support

Baburc10-Dec-15 6:39

Baburc

10-Dec-15 6:39

Hai
I want to create a simple WPF datagrid using vb.net. I added datagrid1 and added 2 columns from designer and binded it from xaml.

XAML
<DataGridTextColumn Binding="{Binding Path=LastName}" ClipboardContentBinding="{x:Null}" CanUserReorder="False" CanUserResize="False" Width="200" Header="LastName" HeaderStringFormat="LastName"/>

Second column

<DataGridTextColumn Binding="{Binding Path=FirstName}" ClipboardContentBinding="{x:Null}" Header="FirstName" HeaderStringFormat="FirstName" CanUserSort="False" CanUserReorder="False" CanUserResize="False" FontSize="16" Width="100">

I use this code
<pre lang="VB.NET">
Private Sub MainWindow_Loaded(sender As Object, e As RoutedEventArgs) Handles Me.Loaded
Dim _customers = New List(Of Customer)
DataGrid1.ItemsSource = _customers
End Sub

Private Sub button_Click(sender As Object, e As RoutedEventArgs) Handles button.Click
&#39;Here I want to add an empty row
End Sub

Public Class Customer
Private _firstName As String
Private _lastName As String

Public Property FirstName() As String
Get
Return _firstName
End Get
Set(ByVal value As String)
_firstName = value
End Set
End Property
Public Property LastName() As String
Get
Return _lastName
End Get
Set(ByVal value As String)
_lastName = value
End Set
End Property
End Class</pre>

My problem is an empty row is automatically added below, I want only to add row in button click event
Please tell me how to do this, or is there any method without using data source
Thanks

Re: Create Simple WPF datagrid

Gerry Schmitz11-Dec-15 7:25

Re: Create Simple WPF datagrid

11-Dec-15 7:25

Try setting the

.CanUserAddRows

property to false on the DataGrid.

Baburc11-Dec-15 7:40

Baburc

11-Dec-15 7:40

Thanks for reply it is working
Also please tell me how to add a new row in button click

Have I done something REALLY dumb?

Mycroft Holmes25-Nov-15 20:29

Mycroft Holmes

25-Nov-15 20:29

No it is a serious question - scenario...

WCF with a single data access class,
A data service class for each table/view in the database. This maps a datatable to the model
A model class for each table/view in the database to be passed in a List<> to the client - implements OnPropertyChanged

WPF client that uses the WCF and retrieves List<> of the models. The client is set to reuse the WCF objects (Models)

This means I do not have to remap the WCF models to client models, however chasing down a potential memory leak I find I have multiple copies of the models in memory. I have 1 particular view with 35 master lists (servicing comboboxes) and another 7 lists used for multi selects over 2 Tabs. Fricking nightmare! This view can take between 2 and 12 seconds to load and I'm attempting to find out why.

So the question should I be passing POCO objects from the WCF and converting them to local models with the OPC implementation?

Never underestimate the power of human stupidity
RAH

Gerry Schmitz26-Nov-15 6:30

26-Nov-15 6:30

Why pass a POCO when only a scalar might be needed?

Mycroft Holmes26-Nov-15 11:50

Mycroft Holmes

26-Nov-15 11:50

I pass all manner of objects, including scalar values. The point is that when I pass a list it is a List<> of a class with the OnPropertyChanged events included rather than a List<> of POCO objects. Is this likely to cause memory leaks?

Never underestimate the power of human stupidity
RAH

Gerry Schmitz26-Nov-15 13:59

26-Nov-15 13:59

The OnPropertyChanged handler is null until a presenter subscribes to it. Can't think of any other references that might cause a problem.

Mycroft Holmes26-Nov-15 22:33

Mycroft Holmes

26-Nov-15 22:33

Tracked the problem down to the binding the selected object to the form, just too many comboboxes, the object has over 50 fields and binds to 30 comboboxes on the one view.

I gave them a couple of options, split the view or change to popups instead of combo boxes. The decided to live with the issue - bloody users.

Never underestimate the power of human stupidity
RAH

Gerry Schmitz27-Nov-15 6:10