public static Expression <Func <T, bool> > Or <T>(this Expression <Func <T, bool> > a, Expression <Func <T, bool> > b)
{
ParameterExpression p = a.Parameters[0];
SubstExpressionVisitor visitor = new SubstExpressionVisitor();
visitor.subst[b.Parameters[0]] = p;
Expression body = Expression.OrElse(a.Body, visitor.Visit(b.Body));
return(Expression.Lambda <Func <T, bool> >(body, p));
}
public static Expression <Func <T, bool> > And <T>(this Expression <Func <T, bool> > a, Expression <Func <T, bool> > b)
{
if (a == null)
{
return(b);
}
ParameterExpression p = a.Parameters[0];
SubstExpressionVisitor visitor = new SubstExpressionVisitor();
visitor.subst[b.Parameters[0]] = p;
Expression body = Expression.AndAlso(a.Body, visitor.Visit(b.Body));
return(Expression.Lambda <Func <T, bool> >(body, p));
}