/// <summary>
/// 初始化 <see cref="AggregateSubqueryExpression"/> 类的新实例。
/// </summary>
/// <param name="groupByAlias">分组表的别名。</param>
/// <param name="aggregateInGroupSelect">聚合运算表达式。</param>
/// <param name="aggregateAsSubquery">聚合子查询表达式。</param>
public AggregateSubqueryExpression(TableAlias groupByAlias, Expression aggregateInGroupSelect, ScalarExpression aggregateAsSubquery)
: base(DbExpressionType.AggregateSubquery, aggregateAsSubquery.Type)
{
AggregateInGroupSelect = aggregateInGroupSelect;
GroupByAlias = groupByAlias;
AggregateAsSubquery = aggregateAsSubquery;
}
/// <summary>
/// 更新 <see cref="AggregateSubqueryExpression"/> 对象。
/// </summary>
/// <param name="subquery">聚合子查询表达式。</param>
/// <returns></returns>
public AggregateSubqueryExpression Update(ScalarExpression subquery)
{
if (subquery != AggregateAsSubquery)
{
return(new AggregateSubqueryExpression(GroupByAlias, AggregateInGroupSelect, subquery));
}
return(this);
}
/// <summary>
/// 访问 <see cref="ScalarExpression"/>。
/// </summary>
/// <param name="scalar">要访问的表达式。</param>
/// <returns></returns>
protected virtual Expression VisitScalar(ScalarExpression scalar)
{
var select = (SelectExpression)Visit(scalar.Select);
return(scalar.Update(select));
}
