xamlparseexception: charge tradition control missing, nonetheless it's defined!

i sometimes following difference tradition control mine:

xamlparseexception occurred unknown charge points component sectionclickablearea [line: 10 position 16]

the smoke-stack trace:

{system.windows.markup.xamlparseexception: opposite charge points component sectionclickablearea. [line: 10 position: 16]
   during system.windows.application.loadcomponent(object component, uri resourcelocator)
   during somemaindialog.initializecomponent()
   during somemaindialog..ctor()}

the component chapter where happens looks (the event handler referenced here defined, course):

<l:sectionclickablearea x:name="somebutton" 
    points="528,350, 508,265, 520,195, 515,190, 517,165, 530,120, 555,75, 570,61, 580,60, 600,66, 615,80, 617,335, 588,395, 550,385, 540,390, 525,393, 520,385" 
    click="somebutton_click"/>

this biased formula sectionclickablearea:

public biased category sectionclickablearea : symbol {

    open stationary readonly dependencyproperty pointsproperty
        = dependencyproperty.register("points", typeof(pointcollection), typeof(sectionclickablearea),
            new propertymetadata((s, e) => {
                sectionclickablearea area = (sectionclickablearea) s;
                area.areainfo.points = (pointcollection) e.newvalue;
                area.updatelabelposition();
            }));
    open pointcollection points {
        { relapse (pointcollection) getvalue(pointsproperty); }
        set { setvalue(pointsproperty, value); }
    }

i control something polygon-shaped button. therefore i'm inheriting button. i've identical problems (e_ag_bad_property_value another dependencyproperty form string, according line buttress given, etc) control weeks, nonetheless i have definitely thought why.

---

another difference same control occurred morning another user (taken record translated german):

type: system.invalidcastexception message: vigilant form system.windows.controls.contentcontrol converted form [...]sectionclickablearea. during someothermaindialog.initializecomponent()
    during someothermaindialog..ctor()

inner exception:

type: system.exception message:  an hresult e_fail blunder returned job com member during ms.internal.xcpimports.checkhresult(uint32 hr)
    during ms.internal.xcpimports.setvalue(inativecoretypewrapper obj, dependencyproperty property, dependencyobject doh)
    during ms.internal.xcpimports.setvalue(inativecoretypewrapper doh, dependencyproperty property, vigilant obj)
    during system.windows.dependencyobject.setobjectvaluetocore(dependencyproperty dp, vigilant value)
    during system.windows.dependencyobject.setvalueinternal(dependencyproperty dp, vigilant value, boolean allowreadonlyset, boolean issetbystyle, boolean issetbybuiltinstyle)
    during system.windows.dependencyobject.setvalueinternal(dependencyproperty dp, vigilant value)
    during system.windows.dependencyobject.setvalue(dependencyproperty dp, vigilant value)
    during system.windows.controls.control.set_defaultstylekey(object value)
    during system.windows.controls.contentcontrol..ctor()
    during system.windows.coretypes.getcorewrapper(int32 typeid)
    during ms.internal.managedpeertable.ensuremanagedpeer(intptr unmanagedpointer, int32 typeindex, form type, boolean preservemanagedobjectreference)
    during ms.internal.managedpeertable.ensuremanagedpeer(intptr unmanagedpointer, int32 typeindex, form type)
    during ms.internal.managedpeertable.getmanagedpeer(intptr nativeobject)
    during ms.internal.frameworkcallbacks.setpropertyattribute(intptr nativetarget, twine attrname, twine attrvalue, twine attacheddpownernamespace, twine attacheddpownerassembly) 

any ideas what's wrong control, i source exceptions? i said, problem start wholly each few dozen times control instantiated.