c# - Attached Property on TextBox WPF -


my problem simple have textbox in wpf can type number. want 3 things when press specific keys :

  • enter : value sent
  • up : value increased sent
  • down : value decreased sent

i have made 3 attached properties works key enter.

<textbox margin="5,0"  hlp:textboxbehaviors.keytovalid="enter" hlp:decrease.keytodecrease="down" hlp:increase.keytoincrease="up"  text="{binding target, mode=twoway, updatesourcetrigger=explicit, converter={staticresource kiloconverter}, validatesonnotifydataerrors=true, validatesonexceptions=true}" />

the code of class :

public static class decrease {     private static key triggeredkey = key.down;     public static key getkeytodecrease(dependencyobject obj)     {         return (key)obj.getvalue(keytodecreaseproperty);     }      /// <summary>     /// sert uniquement à s'attacher à la textbox (une seule fois à l'init de l'interface)     /// </summary>     public static void setkeytodecrease(dependencyobject obj, key value)     {         var tb = obj textbox;         if (tb != null)             tb.keydown += onkeydown;     }      /// <summary>     /// evenement classique     /// </summary>     private static void onkeydown(object sender, keyeventargs e)     {         var tbcurrent = sender textbox;         int selectedpos;          if (tbcurrent != null && e.key == triggeredkey)         {             if (tbcurrent.selectionstart > 0)             {                 if (!tbcurrent.text.contains("."))                 {                     int exp = tbcurrent.text.length - tbcurrent.selectionstart;                     tbcurrent.text = (convert.todouble(tbcurrent.text) - math.pow(10, exp)).tostring();                     selectedpos = tbcurrent.text.length - exp;                 }                 else                 {                     int exp;                     if (tbcurrent.selectionstart > tbcurrent.text.indexof('.') + 1)                     {                         exp = tbcurrent.text.indexof('.') - tbcurrent.selectionstart + 1;                     }                     else if (tbcurrent.selectionstart < tbcurrent.text.indexof('.') + 1)                     {                         exp = tbcurrent.text.indexof('.') - tbcurrent.selectionstart;                     }                     else                     {                         return;                     }                      tbcurrent.text = (convert.todouble(tbcurrent.text) - math.pow(10, exp)).tostring("0.00");                      if (exp < 0)                     {                         selectedpos = tbcurrent.text.indexof('.') - exp + 1;                     }                     else                     {                         if (tbcurrent.text.indexof('.') - exp < 0)                         {                             selectedpos = 0;                         }                         else                         {                             selectedpos = tbcurrent.text.indexof('.') - exp;                         }                     }                 }                  bindingexpression binding = tbcurrent.getbindingexpression(textbox.textproperty);                 if (binding != null)                 {                     binding.updatesource();                 }                  tbcurrent.selectionlength = 0;                 if (selectedpos >= 0)                 {                     tbcurrent.selectionstart = selectedpos;                 }                 else                 {                     tbcurrent.selectionstart = 0;                 }             }         }     }      // using dependencyproperty backing store keytovalid.  enables animation, styling, binding, etc...     public static readonly dependencyproperty keytodecreaseproperty =         dependencyproperty.registerattached("keytodecrease", typeof(key), typeof(textbox), new propertymetadata(triggeredkey));  }

this code decrease attached behavior 2 others designed in same way.

the decrease , increase don't trigger event ! enter does...

the decrease , increase don't trigger event ! enter does...

handle previewkeydown event:

public static void setkeytodecrease(dependencyobject obj, key value) {     var tb = obj textbox;     if (tb != null)         tb.previewkeydown += onkeydown; }

the textbox control handles , "swallows" key presses on own. that's why keydown event isn't fired in behaviour.


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