EF如何分页最大优化

• Z时代
• 2024-01-10
• 分类：综合

publicstaticclass QueryableExtension
    {
publicstatic IQueryable<T> Paged<T>(this IQueryable<T> query, Expression<Func<T, object>> expression, OrderByType orderByType = OrderByType.Desc,int currentPage = 1, int pageSize = 5,int pageCount = 0)
        {
if (currentPage < 1)
            {
                currentPage = 1;
            }
var Skip = (currentPage - 1) * pageSize;
var Take = pageSize;
            OrderByType byType = orderByType;
var MaxPageIndex = pageCount % pageSize == 0 ? pageCount / pageSize : pageCount / pageSize + 1;
if (currentPage > MaxPageIndex / 2)//页码大于一半用倒序
            {
var Mod = pageCount % pageSize;
var Page = (int)Math.Ceiling((Decimal)pageCount / pageSize);
if (currentPage * pageSize >= pageCount)
                {
                    Skip = 0; Take = Mod == 0 ? pageSize : Mod;
                }
else
                {
                    Skip = (Page - currentPage - 1) * pageSize + Mod;
                }
                byType = orderByType == OrderByType.Desc ? OrderByType.Asc : OrderByType.Desc;
            }
else
            {
                byType = orderByType == OrderByType.Desc ? OrderByType.Desc : OrderByType.Asc;
            }
if (pageCount > pageSize)
            {
if (byType == OrderByType.Desc)
                    query = query.OrderByDescending(expression).Skip(Skip).Take(Take);
else
                    query = query.OrderBy(expression).Skip(Skip).Take(Take);
            }
return query;
        }
    }
publicenum OrderByType
    {
        Desc = 2,
        Asc = 1,
    }

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