CODEWITHSUNDEEP
winformsc#-4.0data-bindingcustom-controls
Peter
Peter

Reputation: 864

C# Winforms Custom control, binding on propertychange is not working and causing tabbing issues

I've just upgraded an old .NET 1.1 Winforms app that uses CSLA to .NET 4.0 and a later version of CSLA which supports the use of the INotifyPropertyChanged interface.

A large part of the reason for doing this is the databinding improves - e.g. being able to update on change when binding instead of when validating (tabbing off).

I have custom user control, NumberBox. Essentially it's just a textbox with a few properties such number type, decimal places etc.. I have exposed a public property of type object called BindableValue. It was this property that I was binding my CSLA classes (standard .NET classes inheriting validation rules, property changed and various stuff) integer property to, in this particular case it the class property is integer.

My problem having upgraded are the following:

  1. If I enter a value, e.g. 1234, into my number box control it doesn't push the value back into the class' property it is bound to until I tab off, even though I have configured an object binding source to the custom BindableValue property with the update mode set to Property change.
  2. Having entered value as in (1) if I go back and delete the value I am then prevented from tabbing off or clicking off the number box. I have set VS2010 to throw when .NET exception is thrown but it's not breaking.

It's been a while since I did WinForms stuff so I'm at a bit of a loss where to start. Any tips as well as a solution would be much appreciated.

EDIT: I've tried a number of different things and am getting nowhere fast, it's getting really frustrating now:

  1. I followed the info on MSDN, i.e. I added a ComplexBindingProperties attrib, slightly different in the textbox's private keyUp event handler I raise the event as indicated by the linked article OnBindableValueChanged(). However in all cases my event BindableValueChanged is always null.
  2. I read similar articles to (1) but instead of declaring the event using EventHandler they used PropertyChangedEventHandler, tried this same result.
  3. I added the DefaultBindingProperty attrib.

Upvotes: 0

Views: 1962

Answers (1)

Peter
Peter

Reputation: 864

[You can read about this experience on my companies blog too - OCC Blog - Binding woes ]

I finally figured it out so thought I'd share it here to save someone else the tedium of trawling through Google reading lots of responses that say they work but in .NET 4.0 no longer seem to apply.

Okay, a lot of stuff I was reading on Google kept telling me my usercontrol had to have a Changed event using either EventHandler or PropertyChangedEventHandler delegates - different pages indicated different delegate. I tried both - fail!

What I had to do in .NET 4.0 is actually much nicer. Simply put just like my class that I was binding my usercontrol to does I had to implement the INotifyPropertyChanged interface. Then in my usercontrol when I wanted to pushback into my source object I just raised the PropertyChanged event (e.g. PropertyChanged("BindableValue"); ) the interface defined and hey presto all was well with the world again.

This above is a lot more elegant but unfortunately articles, forums and posts that are indexed by Google have not caught up with this yet for .NET 4.0 so all the existing stuff will lead you down dead ends and much frustration. I hope this saves someone else a lot of time.

Upvotes: 2

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