c# - Binding using ValueConverter - ConvertBack Parameter always null -

i have control bound question, question has many possible options. each option can have response.

example:

question: fit in shoe box?

options: yes, no, maybe

response: options[0].response = new response()

• meaning first option has response, therefore has been answered...

for scenario, have represented using checkbox. if checked, it's answered, if not, response null. hope makes intention clear.

i having problems binding in can't response option. thought i'd able use convert parameter doesn't seem work either..

this how i'm binding check box:

<checkbox  content="{binding text}"             ischecked="{binding response,                        mode=twoway,                         converter={staticresource isquestionresponsenullconverter},                         converterparameter={binding response}}"             /> 

so checkbox value converter, works 1 way using following:

public object convert(object value, type targettype, object parameter, string language)     {         iresponse response = (iresponse )value;          if (response== null)         {             false;         }         return true;     }   

however, want bind using convertback method if check box selected, binding question's response of checkbox's binding context. thought able using converter parameter shown in xaml above, seems parameter null, doing wrong?

i have read on , sources saying dependencyobject required, don't understand why however, surely that's convertback for?

 public object convertback(object value, type targettype, object parameter, string language)     {         if ((bool)value == true)         {             return parameter; //<-- null..          }         else         {             return null;         }     } 

the converter should be:

public class isquestionresponsenullconverter : dependencyobject, ivalueconverter {      public object parameter     {         { return (object)getvalue(parameterproperty); }         set { setvalue(parameterproperty, value); }     }     public static readonly dependencyproperty parameterproperty =         dependencyproperty.register("parameter", typeof(object), typeof(isquestionresponsenullconverter), new propertymetadata(null));        public object convert(object value, type targettype, object parameter, string language)     {         iresponse response = (iresponse)value;          if (response == null)         {             return false;         }         return true;      }      public object convertback(object value, type targettype, object parameter, string language)     {         if ((bool)value == true)         {             return parameter; //get parameter         }         else         {             return null;         }      } } 

and in xaml

  <page.resources>     <local:isquestionresponsenullconverter x:key="isquestionresponsenullconverter" parameter="{binding response}"/> </page.resources>  <grid x:name="grid_master" background="red">      <checkbox verticalalignment="top"  content="{binding text}"         ischecked="{binding response, mode=twoway,  converter={staticresource isquestionresponsenullconverter}}"/>  </grid> 

and in method parameter !

i hope find easy use , useful