需要扩展IQueryable<T>，参数包括一个DateTime类型的属性、开始日期、截止日期。
public static class MyExtension { public static IQueryable<T> WhereDateRange<T>(this IQueryable<T> source, Expression<Func<T, DateTime>> getter, DateTime from, DateTime to) { Expression body = getter.Body; var predicate = Expression.Lambda<Func<T, bool>>( Expression.And(Expression.GreaterThanOrEqual(body, Expression.Constant(from)),Expression.LessThanOrEqual(body, Expression.Constant(to))), getter.Parameters ); return source.Where(predicate); } }
现在可以筛选满足某个日期范围内的集合。比如：
class Program { static void Main(string[] args) { IEnumerable<Pet> pets = new List<Pet> { new Pet {Id=1,Birthday=new DateTime(2014,1,2) }, new Pet {Id=2,Birthday=new DateTime(2015,1,2) }, new Pet {Id=1,Birthday=new DateTime(2016,1,2) } }; var query = pets.AsQueryable().WhereDateRange<Pet>(t => t.Birthday,DateTime.Now.AddYears(-2), DateTime.Now.AddYears(-1)); foreach(var item in query) { Console.WriteLine(item.Birthday.ToShortDateString()); } } } public class Pet { public int Id { get; set; } public DateTime Birthday { get; set; } }