Linq-to-sql查询，其翻译是从逗号分隔的代码到描述的逗号分隔

Question

I've the following tables:

1. "procedures":

   code: bigint, primary key, auto-increment

   caption: varchar(max), not-null

2. "worklist":

   code: bigint, primary key, auto-increment

   title: varchar(max), not-null

   procedures: varchar(max), not-null, comma-separated string of procedure-code

   ...

I'm using Linq-to-SQL to query the table "worklist" with column "procedures" to be translated to comma-separated string of procedure-caption.

eg the sub-query for "worklist"."procedures":

procedures = string.Join(",", (
    from pc in w.procedures.Split(',').Select(cs => long.Parse(cs)).ToList()
    join ps in db.procedures.AsEnumerable() on pc equals ps.code
    select ps.caption
).ToArray()),

However, I'm facing the Exception of "Split() has no supported translation in SQL".

Please kindly advise how to do that. Many Thanks!

Answer 1

you will not be able to solve the query as such. You need to fetch your raw data to c# and afterwards process the split.

This is because in your current code you are asking sql server to do the split and it has no implementation for that. Hence the error...

Answer 2

The following will pass in each item in procList as a separate sql parameter so that it can put it in a sql IN clause. If there's not too many of them, this should work fine.

var procList = w.procedures.Split(',').Select(cs => long.Parse(cs)).ToList();

var procedures = (from ps in db.procedures.AsEnumerable()
    where procList.Contains(ps.Code)
    select ps.Caption).ToArray()

Answer 3

In the query you have shown, you will have to first fetch the records from db using linq query like:

var abc = w.procedures.ToList();

or

var abc = w.procedures.ToList().Select(cs => cs).Split(...);

now on abc you can use any of your string functions.. Because once you do ToList it will fetch the records from database.

Hope this Helps..