WPF (MVVM) - Retrieve the Listbox SelectedItems property

C# .NET Framework 4.0 MVVM Light Toolkit

In my WPF (MVVM) application, I want to use the Listbox SelectedItems property but this property has no setter and for this reason it’s not “bindable“ to my view model.

I have tried to use the property (IsSelected) in my object and in the XAML this item container style.

<ListBox.ItemContainerStyle>

        <Style TargetType="{x:Type ListBoxItem}">

<Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />

        </Style>

</ListBox.ItemContainerStyle>

This solution works fine if the Listbox SelectionMode property is set to Single but if the selection mode is “Extended” (SelectionMode="Extended") it doesn’t work correctly, sometimes a few items remain selected.

Finally, I found a solution that works for me. I use the MenuItem’s CommandParameter for accessing to the Listbox SelectedItems property.

Like this.

<ListBox.ContextMenu>

<ContextMenu>

                    <MenuItem Command="{Binding AddImagesSelectedCommand}" CommandParameter="{Binding PlacementTarget.SelectedItems, RelativeSource={RelativeSource AncestorType={x:Type ContextMenu}}}" Header="{Binding Source={StaticResource CustomResources}, Path=LocalizedStrings.mnuAddImagesSelected}" />

</ContextMenu>

</ListBox.ContextMenu> 

Then in the view model:

AddImagesSelectedCommand = new RelayCommand<object>(OnAddImagesSelected, CanAddImagesSelected);

private void OnAddImagesSelected(object param)

        {

            var selectedImages = ((IEnumerable)param).Cast<CaptureImage>().ToList();

     //To do something …           

        }   

private bool CanAddImagesSelected(object param)

        {

            if (param != null)

            {

                var selectedImages = ((IEnumerable) param).Cast<CaptureImage>().ToList();

                return (selectedImages != null && selectedImages.Count > 0);

            }

            return false;

        }

We must use the PlacementTarget object because the ContextMenu is not in the same part of the Visual Tree, so that is why you cannot use ElementName etc. to reference the ListBox.

See you soon for the next trick!

WPF - Zoom an image with the slider control.

C# .NET Framework 4.0

In a WPF (XAML) view I want to zoom an image using a slider control and also in this occasion the binding help me to do this with a few code rows.

<Grid>

<Grid.RowDefinitions>

             <RowDefinition Height="*"></RowDefinition>

              <RowDefinition Height="30"></RowDefinition>

       </Grid.RowDefinitions>

       <Image Grid.Row="0" Name="ImgReader" Source="Images/Exit.png" Stretch="Uniform" RenderTransformOrigin="0.5, 0.5" >

             <Image.RenderTransform>

                    <ScaleTransform ScaleX="{Binding ElementName=SliderDocument, Path=Value}" ScaleY="{Binding ElementName=SliderDocument, Path=Value}"/>

              </Image.RenderTransform>

       </Image>

       <Slider Grid.Row="1" Name="SliderDocument" VerticalAlignment="Center" Minimum="0.1" Maximum="1" />

</Grid>

It’s great!

Strange error: 'DockingManager' does not exist in XML namespace ...' - Unblock DLL

C# .NET Framework 4.0

I have had a strange error in my WPF application when I referenced an external library (Xceed.Wpf.AvalonDock.dll).

This error

 Error The tag 'DockingManager' does not exist in XML namespace 'http://avalondock.codeplex.com'. Line 41 Position 10.

 appeared at design time but not at run-time, so after a few hours I’ve founded that this was a “security error”, because Windows protects you from components downloaded from the Internet.

After that I clicked on “Unblock” and the error is missed.

Thanks Microsoft … :-|

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Could not load file or assembly Microsoft.Practices.EnterpriseLibrary.Logging exception

C# 4.0, MS Practices Enterprise Library 5.0

I have used the Enterprise Library Configuration tool for creating a Logging Application Block and I have obtained a configuration file like this:

<section name="loggingConfiguration" type="Microsoft.Practices.EnterpriseLibrary.Logging.Configuration.LoggingSettings, Microsoft.Practices.EnterpriseLibrary.Logging, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="true" />

<loggingConfiguration name="" tracingEnabled="true" defaultCategory="General">

                …

                …

</loggingConfiguration>

Unfortunately, I got the following exception while trying to use the Enterprise Library Logging Application Block:

“An error occurred creating the configuration section handler for validation: Could not load file or assembly 'Microsoft.Practices.EnterpriseLibrary.Logging, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)”

I solved this problem by setting to null the PublicKeyToken.

PublicKeyToken=null

Retrieving data from a SQL Server stored procedure using LINQ to entities

C# .NET Framework 4.0, SQL Server 2008, ADO.NET Entity Data Model, LINQ to Entities

I’ve a GetCompanies SQL Server 2008 stored procedure that returns a resultset like this

Field1	Field2	Field3	Field4	Field5	Field6	Field7	Field8
VE	7471	033333333	Environment s.r.l.	1	Roma, 6	Vigonza	35010
VE	7499	033333322	Active s.r.l.	4	Venezia, 8	Padova	35100

So, in my application I want to read this resultset data using LINQ to Entities.

1.       Add a new ADO.NET Entity Data Model (Shapshot.edmx) at the solution.

2.       Follow the wizard for creating a new connection to your database and select the GetCompanies (for this example) stored procedure from the objects list.

3.       Click on Model Browser.

4.       Select the SnapshotModel tree, ComplexTypes.

a.       Right click on CopmplexTypes and then click on “Add new Complex Type”.

b.      Type a name, for example “CompanyEntity”.

                                                               i.      Select CompanyEntity, right click on “Add” -> “Scalar Property” and select the type property: Int32, String, Boolean and so on.

                                                             ii.      In my example I obtain a structure like this

1.       Field1 -> String

2.       Field2 -> Int32

3.       Field3 -> String

4.       Field4 -> String

5.       Field5 -> Int32

6.       Field6 -> String

7.       Field7 -> String

8.       Field8 -> String

c.       Expand the Function Imports folder and double click on GetCompanies stored procedure, you‘ll see a dialog box like this. Select the “Complex” option button and then the type that you have created before.

5.       Now, you can retrieve data using this C# code (Company is an internal object).

GetCompanies() returns a System.Data.Objects.ObjectResult<CompanyEntity> object.

public Company[] GetCompanies()

        {   

            var companiesList = new List<Company>();

            using (var context = new SnapshotEntities())

            {

                var query = context.GetCompanies();

                foreach (var c in query)

                {

                    var company = new Company

                        {

                            Field1 = c.Field1,

                            Field2 = c.Field2,

                            Field3 = c.Field3,

                            Field4 = c.Field4,

                            Field5 = c.Field5,

                            Field6 = c.Field6,

                            Field7 = c.Field7

                            Field8 = c.Field8

                        };

                    companiesList.Add(company);

                }

            }

            return companiesList.ToArray();

        }

That’s all folk!