Calling an object method in a data trigger

Calling a method on an instance of an object in WPF is not as easy to figure out, but with the help of this Internet thing I managed it.

Say you have a DataTemplate that renders a WorkItemType as a button that is selectable:

   1: <DataTemplate DataType="{x:Type tfswitc:WorkItemType}">

   2:     <DockPanel>

   3:         <Image DockPanel.Dock="Left"

   4:                x:Name="wiImage"

   5:                Width="16"

   6:                Height="16"

   7:                Source="pack://application:,,/Resources/Images/WorkItems/unknown.gif">

   8:         </Image>

   9:         <Button x:Name="wiButton"

  10:                 Content="{Binding Name}"

  11:                 Style="{DynamicResource WelcomeButtonStyle}"

  12:                 CommandParameter="{Binding}"

  13:                 Command="Controlers:TeamSystemCommands.ChangeWorkItemTypeCommand">

  14:         </Button>

  15:     </DockPanel>

  16: </DataTemplate>

Now, if I wanted to call a method on an instance of that WorkItemType and perform some action, then I would need a DataTrigger:

   1: <DataTemplate DataType="{x:Type tfswitc:WorkItemType}">

   2:     <DockPanel>

   3:         <Image DockPanel.Dock="Left"

   4:                x:Name="wiImage"

   5:                Width="16"

   6:                Height="16"

   7:                Source="pack://application:,,/Resources/Images/WorkItems/unknown.gif">

   8:         </Image>

   9:         <Button x:Name="wiButton"

  10:                 Content="{Binding Name}"

  11:                 Style="{DynamicResource WelcomeButtonStyle}"

  12:                 CommandParameter="{Binding}"

  13:                 Command="Controlers:TeamSystemCommands.ChangeWorkItemTypeCommand">

  14:         </Button>

  15:     </DockPanel>

  16:     <DataTemplate.Triggers>

  17:         <DataTrigger Value="False">

  18:             <DataTrigger.Binding>

  19:                 <Binding>

  20:                     <Binding.Source>

  21:                         <ObjectDataProvider ObjectType="{x:Type tfswitc:WorkItemType}"

  22:                                             MethodName="SupportedByHeat" />

  23:                     </Binding.Source>

  24:                 </Binding>

  25:             </DataTrigger.Binding>

  26:             <Setter TargetName="wiButton"

  27:                     Property="IsEnabled"

  28:                     Value="False" />

  29:             <Setter TargetName="wiButton"

  30:                     Property="ToolTip"

  31:                     Value="You will need to add the 'HeatITSM.Ref' field to use this work item." />

  32:         </DataTrigger>

  33:     </DataTemplate.Triggers>

  34: </DataTemplate>

This will Call the method and if it returns false, it will disable the button and set a tooltip.

Now, this should work, but my SupportedByHeat method is an Extension method defined as:

   1: Imports Microsoft.TeamFoundation.WorkItemTracking.Client

   2: 

   3: Namespace TeamFoundationExtensions

   4: 

   5: 

   6:     Module WorkItemTypeExtensions

   7: 

   8:         <System.Runtime.CompilerServices.Extension()> _

   9:       Public Function SupportedByHeat(ByVal wit As WorkItemType) As Boolean

  10:             Dim c As Controlers.TeamSystemControler(Of MainWindow)

  11:             c = Application.ControlerFactory.GetControler(Of Controlers.TeamSystemControler(Of MainWindow))()

  12:             Return c.CheckWorkItemField(wit)

  13:         End Function

  14: 

  15:     End Module

  16: 

  17: End Namespace

And this does not seam to work even if I import the namespace in the XAML:

   1: <UserControl x:Class="SelectWorkItemType"

   2:   xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

   3:   xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

   4:   xmlns:d="http://schemas.microsoft.com/expression/blend/2006"

   5:   xmlns:tfs="clr-namespace:Microsoft.TeamFoundation.Client;assembly=Microsoft.TeamFoundation.Client"

   6:   xmlns:tfswitc="clr-namespace:Microsoft.TeamFoundation.WorkItemTracking.Client;assembly=Microsoft.TeamFoundation.WorkItemTracking.Client"

   7:   xmlns:tfse="clr-namespace:Hinshelwood.TFSHeatITSM.TeamFoundationExtensions"

   8:   xmlns:local="clr-namespace:Hinshelwood.TFSHeatITSM"

   9:   xmlns:Controlers="clr-namespace:Hinshelwood.TFSHeatITSM.Controlers"

  10:   xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"

  11:   mc:Ignorable="d">

The error message that is received is:

System.Windows.Data Error: 34 : ObjectDataProvider: Failure trying to invoke method on type; Method=‘SupportedByHeat’; Type=‘WorkItemType’; Error=‘No method was found with matching parameter signature.’ MissingMethodException:‘System.MissingMethodException: Method ‘Microsoft.TeamFoundation.WorkItemTracking.Client.WorkItemType.SupportedByHeat’ not found.
   at System.RuntimeType.InvokeMember(String name, BindingFlags bindingFlags, Binder binder, Object target, Object[] providedArgs, ParameterModifier[] modifiers, CultureInfo culture, String[] namedParams)

_at System.Type.InvokeMember(String name, BindingFlags invokeAttr, Binder binder, Object target, Object[] args, CultureInfo culture)

at System.Windows.Data.ObjectDataProvider.InvokeMethodOnInstance(Exception& e)’_

As you can see, during the binding the extension method is not evaluated.

During my investigation I came across WPFix Part 3 (Extension Methods)  that intoned that there is indeed some solution, but it is complicated requiring the use of Lambda expressions.

I am looking for an easy solution :)

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