Change WPF Textbox Foreground Color on Event -

i change foreground color of textbox based on incoming event (the incoming number differs 1 in textbox) change black if text changed through ui. have working in circuitous way, i'm not sure of correct way it.

the xaml:

<textbox style="{staticresource recparm}" foreground="{binding path=acquisitiontimechangedbyinstrument, converter={staticresource booleantobrush}}"  name="acquisitiontxtbox" textchanged="onacquisitiontimechanged" >     <textbox.text>         <binding path="acquisitiontime" mode="twoway" stringformat="{}{0:f6}" updatesourcetrigger="propertychanged" >             <binding.validationrules>                 <vm:acquisitiontimerule min="200e-6" max="40" />             </binding.validationrules>         </binding>     </textbox.text> </textbox> 

the code behind:

private void onacquisitiontimechanged(object sender, textchangedeventargs e) {     //acquisitiontxtbox.foreground = brushes.black;     ((viewmodel)application.current.resources["vm"]).acquisitiontimechangedbyinstrument = false; } 

acquisitiontimechangedbyinstrument property raises propertychanged on viewmodel. converter change color black false , blue true.

1. in form above, seems work described, seems odd way go it. if use commented line change color directly, binding seems break. is, view stops checking changes acquisitiontimechangedbyinstrument. why?
2. what correct way this?

please keep in mind have been using wpf few days; don't understand advanced features yet.

edit (by request)

eventually check see if value in textbox has changed in acquisitiontime. now, setting acquisitiontimechangedbyinstrument=true when button clicked. send propertychanged event, called if haven't change acquisitiontxtbox.foreground in callback.

[valueconversion(typeof(bool), typeof(solidcolorbrush))] public class booleantobrushconverter : ivalueconverter {     public object convert(object value, type targettype, object parameter, system.globalization.cultureinfo culture)     {         if (null == value)         {             return null;         }         if (value bool)         {             if ((bool)value)             {                 return (solidcolorbrush)brushes.deepskyblue;             }             return (solidcolorbrush)brushes.black;         }          type type = value.gettype();         throw new invalidoperationexception("no type " + type.name);     }      public object convertback(object value, type targettype, object parameter, system.globalization.cultureinfo culture)     {         throw new notimplementedexception();     } } 

setting dependencyproperty locally can take precedence on other settings. effectively, end overwriting binding. use

acquisitiontxtbox.setcurrentvalue(foregroundproperty, brushes.black); 

blog entry explaining setcurrentvalue