.net - Inheritance and Polymorphism in LINQ Lambdas -

i've got couple of classes inheriting base class

public mustinherit class baseclass     public property name string end class  public mustinherit class classa     inherits baseclass     public property string end class  public mustinherit class classb     inherits baseclass     public property somethingelse string end class 

i want able use single expression query multiple lists of objects, of inherit same base class

public function dostuff(expression system.linq.expressions.expression(of func(of baseclass, boolean)))     dim lista new list(of classa) ''populating elsewhere     dim listb new list(of classb) ''and      dim resultseta = lista.where(expression) ''problems on line     dim resultsetb = lista.where(expression) ''and end function 

since both classa , classb inherit same base class, , since linq query against base class, should work. expression can refer properties of base class guaranteed present on both derived classes following compile-time typing error:

value of type 'system.linq.expressions.expression(of system.func(of baseclass, boolean))' cannot converted 'system.linq.expressions.expression(of system.func(of classa, boolean))' 

is there way can add widening conversion (or similar) allow work?

or need provide exact same query multiple times against each derived class?

you need asqueryable() list (c# syntax below)

var resulta = lista.asqueryable().where(expression); 

you can cast results original types if need

 foreach (var x in resulta)  {       response.write(((classa)x).something);  }