/// <summary>
/// 对IEnumerable的分页查询的扩展，用法
/// using ApiServer.Data;
/// [HttpGet]
/// public PagedData{Order} Get(string search, int page, int pageSize, string orderBy, bool desc)
/// {
/// return context.Orders.Paging(context, page, pageSize, orderBy, desc,
/// string.IsNullOrEmpty(search) ? (Func{Order , bool} )null : d => d.Id.HaveSubStr(search) || d.Name.HaveSubStr(search) || d.Content.HaveSubStr(search));
/// }
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="src">IEnumerable<typeparamref name="T"/>的数据集合</param>
/// <param name="context">DbContext对象，src应该在context.Set<typeparamref name="T"/>()能找到</param>
/// <param name="page">需要第几页数据，从1开始，小于1则自动改为1，默认为1</param>
/// <param name="pageSize">每页数据的数量，最小为1，默认为站点默认配置</param>
/// <param name="orderBy">排序的属性名，区分大小写，且属性必须存在于类型<typeparamref name="T"/>中，默认为空</param>
/// <param name="desc">是否是倒序排列，默认是升序</param>
/// <param name="searchPredicate">用来查找或过滤的筛选函数，不需要此功能则传null即可</param>
/// <returns></returns>
public static async Task <PagedData <T> > Paging <T>(this IQueryable <T> src, int page, int pageSize, string orderBy, bool desc, Expression <Func <T, bool> > searchExpression) where T : class, IData
{
var res = new PagedData <T>();
IQueryable <T> data = null;
if (searchExpression == null)
{
data = src;
}
else
{
data = src.Where(searchExpression);
}
if (page < 1)
{
page = 1;
}
if (pageSize < 1)
{
pageSize = 10;
}
res.Total = await data.CountAsync();
res.Page = page;
if (!string.IsNullOrEmpty(orderBy))
{
try
{
data = data.OrderBy(orderBy);
if (desc)
{
data = data.OrderByDescendingBy(orderBy);
}
}
catch { }// orderBy参数有误，比如名称不是类的成员
}
if (((page - 1) * pageSize) > res.Total)
{
res.Data = new List <T>();
res.Size = 0;
}
else
{
try
{
data = data.Skip((page - 1) * pageSize).Take(pageSize);
var datas = await data.ToListAsync();
res.Data = datas;
res.Size = res.Data.Count();
}
catch
{
}
}
return(res);
}
