/// <summary>
/// 返回序列的唯一元素；如果该序列并非恰好包含一个元素，则会引发异常。
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="queryable"></param>
/// <param name="expression"></param>
/// <returns></returns>
public static bool Any <T>(this Queryable <T> queryable, Expression <Func <T, bool> > expression)
{
var type = queryable.Type;
queryable.WhereIndex = queryable.WhereIndex + 100;
ResolveExpress re = new ResolveExpress(queryable.WhereIndex);
re.ResolveExpression(re, expression);
queryable.Where.Add(re.SqlWhere);
queryable.Params.AddRange(re.Paras);
return(queryable.Count() > 0);
}
/// <summary>
/// 专门用于分页控件
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="allItems"></param>
/// <param name="pageIndex"></param>
/// <param name="pageSize"></param>
/// <returns></returns>
public static PagedList <T> ToPagedList <T>(this Queryable <T> allItems, int pageIndex, int pageSize)
{
if (pageIndex < 1)
{
pageIndex = 1;
}
var itemIndex = (pageIndex - 1) * pageSize;
var totalItemCount = allItems.Count();
while (totalItemCount <= itemIndex && pageIndex > 1)
{
itemIndex = (--pageIndex - 1) * pageSize;
}
var pageOfItems = allItems.Skip(itemIndex).Take(pageSize).ToList();
return(new PagedList <T>(pageOfItems, pageIndex, pageSize, totalItemCount));
}
/// <summary>
/// 确定序列是否包含任何元素
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="queryable"></param>
/// <returns></returns>
public static bool Any <T>(this Queryable <T> queryable)
{
return(queryable.Count() > 0);
}