/// <summary>
/// 从 <see cref="IDbQueryable{TSource}"/> 创建 <see cref="List{TSource}"/>
/// </summary>
/// <typeparam name="TSource">source 的元素类型</typeparam>
/// <param name="source">查询序列</param>
/// <returns></returns>
public static List <TSource> ToList <TSource>(this IDbQueryable <TSource> source)
{
return(source.Execute <List <TSource> >());
}
/// <summary>
/// 返回指定序列中满足条件的元素数量
/// </summary>
/// <typeparam name="TSource">source 的元素类型</typeparam>
/// <param name="source">查询序列</param>
/// <param name="predicate">用于测试每个元素是否满足条件的函数</param>
/// <returns></returns>
public static int Count <TSource>(this IDbQueryable <TSource> source, Expression <Func <TSource, bool> > predicate)
{
IDbQueryable <int> query = source.CreateQuery <int>(DbExpressionType.Count, predicate);
return(query.Execute <int>());
}
/// <summary>
/// 返回泛型 <see cref="IDbQueryable{TSource}"/> 中的所有值之和
/// </summary>
/// <typeparam name="TSource">source 的元素类型</typeparam>
/// <typeparam name="TResult">keySelector 的元素类型</typeparam>
/// <param name="source">查询序列</param>
/// <param name="keySelector">应用于每个元素的转换函数</param>
/// <returns></returns>
public static TResult Sum <TSource, TResult>(this IDbQueryable <TSource> source, Expression <Func <TSource, TResult> > keySelector)
{
IDbQueryable <TResult> query = source.CreateQuery <TResult>(DbExpressionType.Sum, keySelector);
return(query.Execute <TResult>());
}
/// <summary>
/// 返回序列中满足指定条件的第一个元素，如果未找到这样的元素，则返回默认值
/// </summary>
/// <typeparam name="TSource">source 的元素类型</typeparam>
/// <param name="source">查询序列</param>
/// <param name="predicate">用于测试每个元素是否满足条件的函数</param>
/// <returns></returns>
public static TSource FirstOrDefault <TSource>(this IDbQueryable <TSource> source, Expression <Func <TSource, bool> > predicate = null)
{
IDbQueryable <TSource> query = source.CreateQuery <TSource>(DbExpressionType.FirstOrDefault, predicate);
return(query.Execute <TSource>());
}
/// <summary>
/// 确定序列是否包含任何元素
/// </summary>
/// <typeparam name="TSource">source 的元素类型</typeparam>
/// <param name="source">查询序列</param>
/// <returns></returns>
/// <param name="predicate">用于测试每个元素是否满足条件的函数</param>
/// <returns>如果源序列中存在元素通过了指定谓词中的测试，则为 true；否则为 false</returns>
public static bool Any <TSource>(this IDbQueryable <TSource> source, Expression <Func <TSource, bool> > predicate)
{
IDbQueryable <bool> query = source.CreateQuery <bool>(DbExpressionType.Any, predicate);
return(query.Execute <bool>());
}
/// <summary>
/// 从 <see cref="IDbQueryable{TSource}"/> 创建 <see cref="DataSet"/>
/// </summary>
/// <typeparam name="TSource">source 的元素类型</typeparam>
/// <param name="source">查询序列</param>
/// <returns></returns>
public static DataSet ToDataSet <TSource>(this IDbQueryable <TSource> source)
{
return(source.Execute <DataSet>());
}