C# 如何迭代 linq-to-sql 查询结果的结果并附加结果？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/10170316/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
How to iterate over results of a linq-to-sql query result and append the results?
提问by codewarrior
I'm new to C# and Linq-to-Sql.
我是 C# 和 Linq-to-Sql 的新手。
I've a table 'InstrumentTypes' of this form:
我有一个这种形式的表“InstrumentTypes”：
typeId(int) | type(varchar) | subttype(varchar)
101 Keys keyboard
102 Keys accessories
103 Guitar acoustic
104 Guitar electric
I need to fetch all 'typeId's from the table based on a search by 'type' as input, and all the typeId's needed to be bound to a ASP Repeater.
我需要根据“type”作为输入进行搜索，从表中获取所有“typeId”，并且需要将所有 typeId 绑定到 ASP 中继器。
So far I've written the following code:
到目前为止，我已经编写了以下代码：
// requestType contains the type from the search
var type = (from m in database.InstrumentTypes
where m.type == requestType
select m);
foreach(var typeId in type)
{
//code
}
I'm unable to figure out how to iterate over the results from the query, store them in a datastructure and bind them to a Repeater.
我无法弄清楚如何迭代查询的结果，将它们存储在数据结构中并将它们绑定到中继器。
The following code binds it to the Repeater:
以下代码将其绑定到中继器：
Repeater1.DataSource= //name of data structure used to store the types goes here
Repeater1.DataBind();
Could anyone please help me out?
有人可以帮我吗？
EDIT: For each typeID obtained, I want to access another table 'Instruments' and retrieve all Instruments belonging to that typeId. The table 'Instruments' is like this:
编辑：对于获得的每个 typeID，我想访问另一个表“Instruments”并检索属于该 typeId 的所有仪器。“仪器”表是这样的：
instrumentId typeID name description
1000 101 yamaha xyz
Based on Arialdo's answer, I'm doing this:
根据 Arialdo 的回答，我正在这样做：
var type = (from m in database.InstrumentTypes
where m.type == requestType
select m);
var instruments = new List<Instrument>();
foreach (var i in type)
{
instruments.Add(from x in database.Instruments
where x.typeId == i.typeId
select x);
}
Repeater1.DataSource = instruments;
Repeater1.DataBind();
But I get a compilation error saying 'The best overloaded method match for the List has some invalid arguments'. Where am I going wrong?
但是我收到一个编译错误，提示“列表的最佳重载方法匹配有一些无效参数”。我哪里错了？
采纳答案by Arialdo Martini
What you get from
你从中得到什么
var type = (from m in database.InstrumentTypes
where m.type == requestType
select m);
is a collection of InstrumentTypes, not a collection of ids.
是 的集合InstrumentTypes，而不是 id 的集合。
This works for me
这对我有用
var types = (from m in database.InstrumentTypes
where m.type == requestType
select m);
var ids = new List<int>();
foreach (var type in types)
{
ids.Add(type.Id);
}
which you could easily convert to
您可以轻松转换为
var ids = (from m in database.InstrumentTypes
where m.type == requestType
select m.Id).ToList();
[Edit]
[编辑]
You can directly query your instruments and navigate to related objects, as long as you defined a relationship between InstrumentTypeand Instrument.
您可以直接查询您的工具并导航到相关对象，只要您定义了InstrumentType和之间的关系Instrument。
var instruments = (from i in database.Instrument
where i.InstrumentType.type == requestType
select i);
No need to have separate foreaches or queries. The i.InstrumentTypewill convert to a join, as you could verify with a SQL profiler
无需单独的foreaches 或查询。在i.InstrumentType将转换为join，因为你可以用SQL事件探查器验证
回答by bkingdev
I am not sure what you are asking.
我不确定你在问什么。
With out explicitly defining the returned type of your query you are already returning an IEnumerable<InstrumentTypes> object. If you want a list of ID's you can simply refine your query to return ID's rather than a list of InstrumentTypes. Of course, then you'd be returning an IEnumerable<int> object.
如果没有明确定义查询的返回类型，您就已经返回了一个 IEnumerable<InstrumentTypes> 对象。如果您想要一个 ID 列表，您可以简单地优化您的查询以返回 ID 而不是 InstrumentTypes 列表。当然，那么您将返回一个 IEnumerable<int> 对象。
var type = (from m in database.InstrumentTypes
where m.type == requestType
select m.typeId);
