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A Scottish dyslexic software developer: Team System MVP, .NET architect, developer, evangelist, technology enthusiast and multi-dimensional free thinker


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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 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 :)


posted @ Wednesday, August 27, 2008 11:16 AM | Filed Under [ Microsoft .NET Framework WPF TFS Heat ITSM ]

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