/// <summary>
/// Extendable method: 获取分页查询数据源
/// </summary>
/// <typeparam name="TEntity">实体类型</typeparam>
/// <param name="source">排好序的数据源</param>
/// <param name="pageSize">每页的元素数量</param>
/// <param name="pageIndex">当前第几页</param>
/// <returns>分页查询数据源</returns>
public static IDbPagedQuery <TEntity> Paging <TEntity>(this IDbSortedQuery <TEntity> source, int pageSize, int pageIndex = 1)
where TEntity : class
{
//非空检查
Check.ArgumentNull(source, nameof(source));
//执行分页查询
return(source.Factory.CreatePagedQuery(source, pageSize, pageIndex));
}
/// <summary>
/// Extendable method: 对排好序的数据源再次降序排序
/// </summary>
/// <typeparam name="TEntity">实体类型</typeparam>
/// <typeparam name="TKey">实体属性类型</typeparam>
/// <param name="source">排好序的数据源</param>
/// <param name="keySelector">指定某属性的表达式</param>
/// <returns>再次排好序的数据源</returns>
public static IDbSortedQuery <TEntity> ThenByDescending <TEntity, TKey>(this IDbSortedQuery <TEntity> source, Expression <Func <TEntity, TKey> > keySelector)
where TEntity : class
{
//非空验证
Check.ArgumentNull(source, nameof(source));
Check.ArgumentNull(keySelector, nameof(keySelector));
//创建新的查询对象
return(source.Factory.CreateSortedQuery(source, keySelector, true));
}
/// <summary>
/// Extendable method: 查询前几条的元素
/// </summary>
/// <typeparam name="TEntity">object's type</typeparam>
/// <param name="source">数据源</param>
/// <param name="topCount">查询的前几条的元素数量</param>
/// <returns>TOP查询数据源</returns>
public static IDbSelectedQuery <TEntity> Top <TEntity>(this IDbSortedQuery <TEntity> source, int topCount)
where TEntity : class
{
//非空检查
Check.ArgumentNull(source, nameof(source));
Check.ArgumentNull(topCount, nameof(topCount));
//获取TOP查询数据源
return(source.Factory.CreateTopSelectedQuery(source, topCount));
}
/// <summary>
/// Extendable method: 查询前几条选定项
/// </summary>
/// <typeparam name="TEntity">object's type</typeparam>
/// <typeparam name="TResult">result's type</typeparam>
/// <param name="source">数据源</param>
/// <param name="topCount">查询的前几条的元素数量</param>
/// <param name="selector">指定选定项的表达式</param>
/// <returns>TOP选定项查询数据源</returns>
public static IDbSelectedQuery <TResult> Top <TEntity, TResult>(this IDbSortedQuery <TEntity> source, int topCount, Expression <Func <TEntity, TResult> > selector)
where TEntity : class
{
//非空检查
Check.ArgumentNull(source, nameof(source));
Check.ArgumentNull(topCount, nameof(topCount));
Check.ArgumentNull(selector, nameof(selector));
//获取TOP查询数据源
return(source.Factory.CreateTopSelectedQuery(source, topCount, selector));
}
