使用Entity Framework时，如何构建动态排序条件

/// <summary> /// 分页查询 /// </summary> /// <param name="query"></param> /// <param name="start"></param> /// <param name="limit"></param> /// <param name="sort">排序字段</param> /// <param name="dir">ASC/DESC</param> /// <param name="count">总纪录数</param> /// <returns></returns> public List<T> PageList(IQueryable<T> query, int start, int limit, string sort, string dir, out int count) { if (string.IsNullOrEmpty(sort)) throw new Exception("使用此方法,必须指定排序字段!"); ParameterExpression param = Expression.Parameter(typeof(T), "it"); Expression body = param; if (Nullable.GetUnderlyingType(body.Type) != null) body = Expression.Property(body, "Value"); PropertyInfo sortProperty = typeof(T).GetProperty(sort, BindingFlags.Public | BindingFlags.Instance | BindingFlags.IgnoreCase); if (sortProperty == null) throw new Exception("对像上不存在" + sortProperty + "的字段"); body = Expression.MakeMemberAccess(body, sortProperty); LambdaExpression keySelectorLambda = Expression.Lambda(body, param); string queryMethod = dir == "DESC" ? "OrderByDescending" : "OrderBy"; query = query.Provider.CreateQuery<T>(Expression.Call(typeof(Queryable), queryMethod, new Type[] { typeof(T), body.Type }, query.Expression, Expression.Quote(keySelectorLambda))); count = query.Count(); if (start >= 0 && limit > 0) query = query.Skip(start).Take(limit); return query.ToList(); }