wpf - Silverlight: Missing DependencyObject.CoerceValue -

in silverlight there no dependencyobject.coercevalue. looking alternative, following wpf-code in silverlight.

the situation: there class range, has several dependencyproperties: minimumproperty, maximumproperty, lowervalueproperty , uppervalueproperty.

minimum may never greater maximum, maximum never smaller minimum. lowervalue , uppervalue have in between minimum , maximum, whereas lowervalue smaller uppervalue.

all dependencyproperties implemented (in wpf):

public static new readonly dependencyproperty minimumproperty =      dependencyproperty.register("minimum",      typeof(double),      typeof(range),      new frameworkpropertymetadata(0d,        new propertychangedcallback(range.onminimumchanged),        new coercevaluecallback(range.coerceminimum)),      new validatevaluecallback(range.validateminimum));  public new double minimum     {       { return (double)base.getvalue(minimumproperty); }       set { base.setvalue(minimumproperty, value); }     } 

the coercion in wpf done that:

private static object coerceminimum(dependencyobject source, object value) {   range r = source range;   double maximum = r.maximum;   double val = (double)value;   if (val > maximum)   {     return maximum;   }   return value; } 

propertychangedcallback looks this:

private static void onminimumchanged(dependencyobject source, dependencypropertychangedeventargs e) {   range r = source range;   r.coercevalue(lowervalueproperty);   r.coercevalue(uppervalueproperty);   r.coercevalue(maximumproperty); } 

the validatevaluecallback doesn't matter in case. other callbacks similar shown code.

in wpf runs good. example set (in xaml)

<range lowervalue="12" minimum="10" uppervalue="15" maximum="20" /> 

all values correct. order doesn't matter!

but in silverlight not running.

first step workaround coercevaluecallback. raise coercion in propertychangedcallback, this:

private static void onminimumchanged(dependencyobject source, dependencypropertychangedeventargs e) {   range r = source range;   double newval = (double)e.newvalue;   double coercedval = (double)coerceminimum(source, newval);   if (coercedval != newval)   {     r.minimum = coercecval;     return;   }    r.coercevalue(lowervalueproperty);   r.coercevalue(uppervalueproperty);   r.coercevalue(maximumproperty); } 

if minimum set value, coerceminimum still executed , minimum-coercion done well.

but last 3 lines not compile, because dependencyobject has no coercevalue-method. , position @ one's wits' end.

how raise coercion lowervalue, uppervalue , maximum on minimumchanged? or there way ensure, order of initialization not matter , properties set correctly (assuming condition fulfilled)?

thanks in advance!

i got solution :) sure, isnt completed yet. i've still debug possible orders, think done.

i post code lowervalue, others same:

• onuppervaluechanged raise coerceuppervaluechanged , coercelowervaluechanged.
• onminimumchanged raise coerceminimum, coerceuppervaluechanged , coercelowervaluechanged.
• onmaximumchanged raise coercemaximum, coerceuppervaluechanged , coercelowervaluechanged.

the coercion of minimum , maximum easy. if new value greater maximum (or smaller minimum) take maximum (or minimum), else take new value.

here's code:

private static void onlowervaluechanged(dependencyobject source, dependencypropertychangedeventargs e) {   range r = source range;    if (r._levelsfromrootcall == 0)   {     r._requestedlowerval = (double)e.newvalue;   }    r._levelsfromrootcall++;   r.coercelowervalue();    r.coerceuppervalue();   r._levelsfromrootcall--; }  private void coercelowervalue() {   double minimum = this.minimum;   double maximum = this.maximum;   double lowerval = this.lowervalue;   double upperval = this.uppervalue;   if (lowerval != _requestedlowerval && _requestedlowerval >= minimum && _requestedlowerval <= maximum)   {     if (_requestedlowerval <= upperval)     {       base.setvalue(lowervalueproperty, _requestedlowerval);     }     else     {       base.setvalue(lowervalueproperty, upperval);     }   }   else   {     if (lowerval < minimum)     {       base.setvalue(lowervalueproperty, minimum);     }     else if (lowerval > upperval || _requestedlowerval > upperval)     {       base.setvalue(lowervalueproperty, upperval);     }     else if (lowerval > maximum)     {       base.setvalue(lowervalueproperty, maximum);     }   } }