As per the Programmer's guide, selection rectangle is drawn only when you hold control key and left mouse button or else it is drawn when you set the RightButtonActions or MiddleButtonActions to Select.

Is it possible to drawn selection rectangle without holding the Control key and dragging the mouse holding leftbutton.

Diagram.Behavior = Modify is already set. Diagram canvas allows mutiple selection also. But selection rectangle is not shown on the screen. It appears only when I hold control key

I have replaced the dll file and designer give me following error
Could not load type 'System.Windows.Media.Effects.Effect' from assembly 'PresentationCore, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'.
   at System.Signature._GetSignature(SignatureStruct& signature, Void* pCorSig, Int32 cCorSig, IntPtr fieldHandle, IntPtr methodHandle, IntPtr declaringTypeHandle)
   at System.Signature.GetSignature(SignatureStruct& signature, Void* pCorSig, Int32 cCorSig, RuntimeFieldHandle fieldHandle, RuntimeMethodHandle methodHandle, RuntimeTypeHandle declaringTypeHandle)
   at System.Signature..ctor(RuntimeMethodHandle methodHandle, RuntimeTypeHandle declaringTypeHandle)
   at System.Reflection.RuntimeMethodInfo.get_Signature()
   at System.Reflection.RuntimeMethodInfo.GetParametersNoCopy()
   at System.Reflection.RuntimePropertyInfo.GetIndexParameters()
   at MS.Internal.Xaml.ReflectionTypeNode.BuildProperties()
   at MS.Internal.Xaml.ReflectionTypeNode.Find(Identifier name, Boolean includeAttachable)
   at MS.Internal.Xaml.XmlElement.ConvertAttributes(XamlObjectElement objectElement, XamlElement parent, TypeNode typeNode, PrefixScope scope, IParseContext context)
   at MS.Internal.Xaml.XmlElement.ConvertToXaml(XamlElement parent, PrefixScope parentScope, IParseContext context, IMarkupSourceProvider provider)
   at MS.Internal.Xaml.XmlElement.ConvertChildrenToXaml(XamlElement result, PrefixScope scope, IParseContext context, IMarkupSourceProvider provider, Boolean childrenAsString)
   at MS.Internal.Xaml.XmlElement.ConvertToXaml(XamlElement parent, PrefixScope parentScope, IParseContext context, IMarkupSourceProvider provider)
   at MS.Internal.Xaml.XmlElement.ConvertChildrenToXaml(XamlElement result, PrefixScope scope, IParseContext context, IMarkupSourceProvider provider, Boolean childrenAsString)
   at MS.Internal.Xaml.XmlElement.ConvertToXaml(XamlElement parent, PrefixScope parentScope, IParseContext context, IMarkupSourceProvider provider)
   at MS.Internal.Xaml.XmlElement.ConvertChildrenToXaml(XamlElement result, PrefixScope scope, IParseContext context, IMarkupSourceProvider provider, Boolean childrenAsString)
   at MS.Internal.Xaml.XmlElement.ConvertToXaml(XamlElement parent, PrefixScope parentScope, IParseContext context, IMarkupSourceProvider provider)
   at MS.Internal.Xaml.XmlElement.ConvertChildrenToXaml(XamlElement result, PrefixScope scope, IParseContext context, IMarkupSourceProvider provider, Boolean childrenAsString)
   at MS.Internal.Xaml.XmlElement.ConvertToXaml(XamlElement parent, PrefixScope parentScope, IParseContext context, IMarkupSourceProvider provider)
   at MS.Internal.Xaml.XmlElement.ConvertChildrenToXaml(XamlElement result, PrefixScope scope, IParseContext context, IMarkupSourceProvider provider, Boolean childrenAsString)
   at MS.Internal.Xaml.XmlElement.ConvertToXaml(XamlElement parent, PrefixScope parentScope, IParseContext context, IMarkupSourceProvider provider)
   at MS.Internal.Xaml.XmlElement.ConvertChildrenToXaml(XamlElement result, PrefixScope scope, IParseContext context, IMarkupSourceProvider provider, Boolean childrenAsString)
   at MS.Internal.Xaml.XmlElement.ConvertToXaml(XamlElement parent, PrefixScope parentScope, IParseContext context, IMarkupSourceProvider provider)
   at MS.Internal.Xaml.XmlElement.ConvertChildrenToXaml(XamlElement result, PrefixScope scope, IParseContext context, IMarkupSourceProvider provider, Boolean childrenAsString)
   at MS.Internal.Xaml.XmlElement.ConvertToXaml(XamlElement parent, PrefixScope parentScope, IParseContext context, IMarkupSourceProvider provider)
   at MS.Internal.DocumentTrees.Markup.XamlSourceDocument.FullParse(Boolean convertToXamlWithErrors)
   at MS.Internal.DocumentTrees.Markup.XamlSourceDocument.ConvertToSkeleton()
   at Microsoft.Windows.Design.Documents.MarkupDocumentManager.BuildSkeleton(IMarkupSo
urceProvider source)
   at Microsoft.Windows.Design.Documents.MarkupDocumentManager.<>c__DisplayClass4.<Loa
d>b__0()
   at Microsoft.Windows.Design.ServiceManager.PublishProxy`1.PublishService(Type serviceType)
   at Microsoft.Windows.Design.EditingContext.DefaultServiceManager.GetService(Type serviceType)
   at Microsoft.Windows.Design.EditingContext.DefaultServiceManager.Subscribe(Type serviceType, SubscribeServiceCallback callback)
   at Microsoft.Windows.Design.ServiceManager.Subscribe[ServiceType](SubscribeServiceCallback`1 callback)
   at MS.Internal.SelectionTracking.SelectionTracker..ctor(EditingContext context)
   at MS.Internal.Designer.VSDesigner.Load()
   at MS.Internal.Designer.VSIsolatedDesigner.VSIsolatedView.Load()
   at MS.Internal.Designer.VSIsolatedDesigner.VSIsolatedDesignerFactory.Load(IsolatedV
iew view)
   at MS.Internal.Host.Isolation.IsolatedDesigner.BootstrapProxy.LoadDesigner(Isolated
DesignerFactory factory, IsolatedView view)
   at MS.Internal.Host.Isolation.IsolatedDesigner.BootstrapProxy.LoadDesigner(Isolated
DesignerFactory factory, IsolatedView view)
   at MS.Internal.Host.Isolation.IsolatedDesigner.Load()
   at MS.Internal.Designer.DesignerPane.LoadDesignerView()


Please help

Thanks It worked.

Diagram canvas shows Trial Version. We have a license copy. Can you please tell me how can i get the updated copy of the WPFDiagram with the above fix.

Selection rectangle is appearing properly now.
But found one problem while working on it.

Sometimes the Selection rectangle effect appears when it shouldn’t. 

I have a custom property control and when you select a diagram node, its property is displayed in right panel. At this point the focus is in the text box of the custom property control.  Moving off the textbox will bring up the warning “It should be unique” – this is fine.

However depending on how you move off of the textbox will dictate whether the strange Selection rectangle effect takes place.  E.g. If you are in the textbox (i.e. it has focus) and you click the canvas, then you are presented with the “It should be unique” warning – click the ok button to get rid of this and as you move the mouse around you will see a Selection rectangle effect.

Thanks so much. It worked

Right, this version should also fix the DrawLinks case:
https://mindfusion.eu/_temp/wpf_selfix.zip

We've reused the archive file name. That's a new wpf_selfix.zip, containing an updated set of assemblies that should fix the DrawLinks behavior too. Or have you tried them and found it's still buggy?

Stoyan