Access Datacontext And A Property In Code Behind At The Same Time

I am using MVVM/WPF and trying to do something seemingly simple, but cant find a clean solution.

I want to do the following:

When a property changes in the model (WPF Textbox text would be changed in this case), use a method to perform other operations on the UI relating to the property bound.

Currently i am using a multibinding on the tooltip (to get the textbox datacontext + binding path), but this is a bit of a hack.

<TextBox x:Name="textBox" Text="{Binding Model.MyProperty}">
 <TextBox.ToolTip>
        <MultiBinding Converter="{StaticResource brNewMultiConverter}">
                <!-- This to trigger the converter in all required cases. 
                     Without it, i cant get the event to fire when filling 
                     the model initially 
                 -->
                <Binding ElementName="textBox" Path="Text" />
                <!-- This has the properties i need, but wont fire without 
                     the binding above -->
            开发者_开发问答    <Binding ElementName="textBox" />
        </MultiBinding>
 </TextBox.ToolTip>
</TextBox>

I would like to make something re-usable and maybe for different controls, hence i am not just using the textchanged event.

If anyone could point me in the right direction, it would be much appreciated.

OK, so far as your Multibinding there, what are you trying to accomplish there? I don't know what your converter is supposed to do, but can it not be done with an IValueConverter implementing class? I am assuming not, it looks like you are passing the textbox to the converter.

As far as having a method do several things when your model properties get updated, you can have the viewmodel subscribe to events on your model class. Just declare the object WithEvents (VB.NET) and add event handlers for On[PropertyName]Changed.

When implementing MVVM, I tend to treat the codebehind as a second class citizen. I do my best to push all logic off to the ViewModel or View if I can. I have almost completely stopped using Converters as much of that logic can be duplicated in ViewModels, and if it is something that I want to re-use, I usually just have a little helper class that gets whatever passed to it, does something, and passes it back out. I have never really had that great a relationship with IValueConverter...

Other than that, it is unclear exactly what you are trying to do. Could we get some more clarification?

It looks like you're trying to have the tooltip have the content of the textbox, if so why not just do this?

<TextBox Text="{Binding Model.MyProperty}" ToolTip="{Binding Model.MyProperty}"/>

If that's not what you want, but want the tooltip to change based on the value of the textbox then do that in your viewmodel e.g.

public class MyViewModel
{
  string _MyProperty;
  public string MyProperty
  {
    get { return _MyProperty;}
    set 
    { 
       _MyProperty = value; 
       OnPropertyChanged("MyProperty");
       OnPropertyChanged("MyToolTipProperty"); //force WPF to get the value of MyToolTipProperty
    }
  }

  public string MyToolTipProperty
  {
    get 
    { 
      //return what you want
    }

  }
}

and then in your markup:

<TextBox Text="{Binding Model.MyProperty}" ToolTip="{Binding Model.MyToolTipProperty}"/>