wpf - ComboBox SelectedValue not changing from binding to Dependency Property -

i have custom control:

i don't want specifics simplicity's sake have 3 dependency properties :

mycustomcontrol (cs) :

public class mycustomcontrol : control {     dp value1     dp internalvalue     dp selectedvalue       onvalue1changed()    {        internalvalue = calculatebasedon1();    }     static bool _issetinternally;      oninternalvaluechanged()    {        if(condition())        {            _issetinternally = true;            selectedvalue = e.newvalue;        }        else        {            value1 = fixvalue1();                                }     }     onselectedvaluechanged()    {        if(_issetinternally)        {           _issetinternally = false;           return;         }         value1 = extractvalue1frominput(e.newvalue);    }     public list<string> values    {        get{ return new list<string>() { "1","2",......,"200"};}    }   } 

my controltemplate (again simplified) :

    <controltemplate>         <combobox x:name="cb"             itemssource="{binding relativesource={relativesource templatedparent}, mode=oneway, path=values}"            selecteditem={binding relativesource={relativesource templatedparent}, path=value1, mode=twoway, updatesourcetrigger=propertychanged}     </controltemplate> 

the problem : cb showing last value chosen , after fixed explained below .

flow :

1) input :

1.1) selectedvalue bound property in datacontext , receives value.

1.2) onselectedvaluechanged() sets value1.

1.3) value1 sets "cb" selecteditem via binding.

1.4) onvalue1changed sets internalvalue.

1.5) oninternalvaluechanged() flags _issetinternally = true , updates selectedvalue.

1.6) onselectedvaluechanged() zeros _issetinternally = false , stops flow (return).

2) output :

2.1) cb's selecteditem changed.

2.2) value1 set via binding.

2.3) onvalue1changed() sets internalvalue.

2.4) if condition met propagate output.

2.4.1) go (1.4)

2.4.2) problem , condition not met, set value1 again valid value.

2.5) go (1.4)

the problem in 2.4.2 combobox still showing non - valid value chosen in (2.1)

observing snoop can see selecteditem correct , have been changed , selectedvalue , selectedindex still one's chosen before fix.

*further more iv'e attempted coerce value1 on coercion callback , had same effect.

any idea's why combobox doesn't update it's value via binding in scenario ?

i don't know if did understand problem, should have binding selecteditem in combobox.

when value changes, should raise propertychanged event inotifypropertychanged.

in combo, have properties displaymemberpath , selectedvaluepath.

can work it?

regards,