public Func <TSource, TResult> CreateSelector <TSource, TResult>()
{
// if we are selecting * then result type should equal source type
if (AllColumns)
{
return(ExpressionFactory.CreateIdentitySelector <TSource, TResult>().Compile());
}
// if selecting only one field create a simple selection function
IEnumerable <string> fields = Columns.GetFieldList();
if (fields.Count() == 1)
{
return(ExpressionFactory.CreateSinglePropertySelector <TSource, TResult>(fields.First()).Compile());
}
// if TResult is dynamic return an expando object
if (typeof(TResult) == typeof(object))
{
return(ExpressionFactory.CreateExpandoSelector <TSource, TResult>(fields, Columns.GetResultList()).Compile());
}
// if return type has an empty constructor use it and memberinit
if (typeof(TResult).HasEmptyConstructor())
{
return(ExpressionFactory.CreateMemberInitSelector <TSource, TResult>(fields, Columns.GetResultList()).Compile());
}
// otherwise try and use a constructor that matches the field list types
Type[] resultTypes = typeof(TSource).GetPropertyOrFieldTypes(fields);
return(ExpressionFactory.CreateConstructorCallSelector <TSource, TResult>(fields, resultTypes).Compile());
}