/// <summary>
/// Extendable method: 统计实体数据源中符合条件的元素某属性的和
/// </summary>
/// <typeparam name="TEntity">实体类型</typeparam>
/// <param name="source">数据源</param>
/// <param name="selector">指定实体某属性表达式</param>
/// <param name="predicate">筛选条件表达式</param>
/// <returns>实体数据源中符合条件的元素某属性的和</returns>
public static decimal Sum <TEntity>(this IDbQuery <TEntity> source, Expression <Func <TEntity, decimal?> > selector, Expression <Func <TEntity, bool> > predicate)
where TEntity : class
{
return(source.Function("Sum", selector, predicate));
}
/// <summary>
/// Extendable method: 获取实体数据源中所有实体某属性的平均值
/// </summary>
/// <typeparam name="TEntity">实体类型</typeparam>
/// <param name="source">数据源</param>
/// <param name="selector">指定实体某属性表达式</param>
/// <returns>实体数据源中所有实体某属性的平均值</returns>
public static decimal Avg <TEntity>(this IDbQuery <TEntity> source, Expression <Func <TEntity, decimal?> > selector)
where TEntity : class
{
return(source.Function("Avg", selector));
}
/// <summary>
/// Extendable method: 统计实体数据源中所有元素某属性的和
/// </summary>
/// <typeparam name="TEntity">实体类型</typeparam>
/// <param name="source">数据源函数执行器</param>
/// <param name="selector">指定实体某属性表达式</param>
/// <returns>实体数据源中所有元素某属性的和</returns>
public static double Sum <TEntity>(this IDbQuery <TEntity> source, Expression <Func <TEntity, double?> > selector)
where TEntity : class
{
return(source.Function("Sum", selector));
}
/// <summary>
/// Extendable method: 获取实体数据源中符合条件的实体某属性的平均值
/// </summary>
/// <typeparam name="TEntity">实体类型</typeparam>
/// <param name="source">数据源</param>
/// <param name="selector">指定实体某属性表达式</param>
/// <param name="predicate">筛选条件表达式</param>
/// <returns>实体数据源中符合条件的实体某属性的平均值</returns>
public static double Avg <TEntity>(this IDbQuery <TEntity> source, Expression <Func <TEntity, double?> > selector, Expression <Func <TEntity, bool> > predicate)
where TEntity : class
{
return(source.Function("Avg", selector, predicate));
}