Windows Phone 7 database, table null reference Problem

In datacontext, a table is added,CodeAs follows:

     ///   <Summary>  
  ///  Data access context
  ///   </Summary>  
      Public   Class Sysdatacontext: datacontext
{
 Public   Static   String Dbconnectionstring ="  Data Source = isostore:/sys. SDF; Case Sensitive = true;  " ;

 Public Sysdatacontext ()
: Base (Dbconnectionstring)
{
}

 Public Table <tabletestentity> tabletestentities { Get ; Set ;}
}

As a result, when accessing tabletestentities, a blank reference exception is prompted. Modify the following to solve the problem:

    ///   <Summary>  
  ///  Data access context
  ///   </Summary>  
      Public   Class Sysdatacontext: datacontext
{
 Public   Static   String Dbconnectionstring = " Data Source = isostore:/sys. SDF; Case Sensitive = true;  " ;

 Public Sysdatacontext ()
: Base (Dbconnectionstring)
{
}

 Public Table <tabletestentity> tabletestentities; //  {Get; set ;}  
 }

 

Linqtosql reflects that the query should be based on field, rather than the property, leading to a null reference error.