c# - WPF - Bound Control Not Updating When Property Changed? -

i've bound text property of textbox base object's property , seems work fine. unfortunately, when programatically change value of property, doesn't seem update on gui.

here's property:

public string sealeddate {         {         string result = string.empty;          if (_dacase.sealeddate != datetime.minvalue)         {             result = formatting.formatdate(_dacase.sealeddate);         }          return result;     }     set     {         datetime thedate = datetime.minvalue;          if (datetime.tryparse(value, out thedate)             && _dacase.sealeddate != thedate)         {             _dacase.sealeddate = thedate;             base.onchanged(); //fires event know value of object has changed         }     } } 

and value of property being set when property being set:

public bool issealed {         {         return _dacase.sealedid > 0             || _dacase.sealeddate != datetime.minvalue;     }     set     {         if (value != (_dacase.sealedid > 0 || _dacase.sealeddate != datetime.minvalue))         {             if (value)             {                 this.sealedid = authentication.currentuser.id;                 this.sealeddate = formatting.formatdate(datetime.now);             }             else             {                 this.sealedid = 0;                 this.sealeddate = datetime.minvalue.tostring();             }             base.onchanged();         }     } } 

and xaml of textbox isn't updating when think should:

<textbox name="txtsealeddate" text="{binding sealeddate}" grid.column="5" grid.row="3" isreadonly="true" /> 

vlad's solution (in comments) correct.