c# - ComboBox SelectedItem Binding does not work -

i have datagrid 4 columns.

<datagrid itemsource="{binding mydataset,mode=twoway}">     <datagrid.columns>          <datagridtemplatecolumn>             <datagridtemplatecolumn.celltemplate>                 <datatemplate>                     <textblock ...../>                 </datatemplate>             </datagridcolumn.celltemplate>         </datagridtemplatecolumn>          <datagridtemplatecolumn>             <datagridtemplatecolumn.celltemplate>                 <datatemplate>                     <textblock ...../>                 </datatemplate>             </datagridcolumn.celltemplate>         </datagridtemplatecolumn>          <datagridtemplatecolumn>             <datagridtemplatecolumn.headertemplate>                 <datatemplate>                     .............                 </datatemplate>             </datagridtemplatecolumn.headertemplate>             <datagridtemplatecolumn.celltemplate>                 <datatemplate>                     <combobox itemsource ="{binding firstcomboboxdata }" selecteditem="{binding firstcomboboxselectedval}"/>                 </datatemplate>             </datagridcolumn.celltemplate>         </datagridtemplatecolumn>          <datagridtemplatecolumn>             <datagridtemplatecolumn.celltemplate>             <datatemplate>                 <datatemplate>                     <combobox itemsource ="{binding secondcomboboxdata }" selecteditem="{binding secondcomboboxselectedval}"/>                 </datatemplate>             </datagridcolumn.celltemplate>         </datagridtemplatecolumn>      </datagrid.columns> </datagrid> 

the model class mydata in following.

class mydata : observableobject {     private string _code;     public string code     {         set { _code = value ; onpropertychanged("code");}         { return _code ;}     }      private string _name;     public string name     {         set { _name = value ; onpropertychanged("name");}         { return _name ;}     }      private list<someotherclass> _firstcomboboxdata;     public list<someotherclass> firstcomboboxdata     {         set { _firstcomboboxdata = value ; onpropertychanged("firstcomboboxdata");}         { return _firstcomboboxdata ;}     }       private list<someotherclass> _secondcomboboxdata;     public list<someotherclass> secondcomboboxdata     {         set { _secondcomboboxdata = value ; onpropertychanged("secondcomboboxdata");}         { return _secondcomboboxdata ;}     }      private someotherclass _firstcomboboxselectedval;     public someotherclass name     {         set { _firstcomboboxselectedval= value ; onpropertychanged("firstcomboboxselectedval");}         { return _firstcomboboxselectedval;}     }      private someotherclass _secondcomboboxselectedval;     public someotherclass secondcomboboxselectedval     {         set { _secondcomboboxselectedval= value ; onpropertychanged("secondcomboboxselectedval");}         { return _secondcomboboxselectedval;}     }   } class someotherclass {     private int id;      public int id     {         set { id = value ; onpropertychanged("id");}         { return id ;}     } } 

then have following list in viewmodel.

 private observablecollection<mydata> _mydataset;  public  observablecollection<mydata> mydataset  {      set { _mydataset=value; onpropertychanged ("mydataset"); }      { return _mydataset ;}  } 

i see fine. when change selected item of said comboboxes, mydataset's relevant firstcomboboxselectedval or secondcomboboxselectedval not updated

have done wrong somewhere?