Asp.net mvc linq

如何解决Asp.net mvc linq

我有 Item 表和该项目的 Transaction 表。

我的项目表就像

[ID] [Item_Name]

001，苹果

002，香蕉

这是我的交易表

[ID] [成交价格] [成交日期]

001，1 $，2020/3/10

001，1.5 $，2020/04/10

001，2 $，2020/05/10

002，1 $，2020年10月10日

002，1.2 $，2020/04/10

002，1.3 $，2020/3/10

我想得到这样的

苹果以2美元的价格出售。

香蕉以1.3美元的价格售出。

我想知道的是如何获得所售商品的最后价格。我还想加入两个桌子并获得商品的最后价格。

我尝试过

var soldprice = (from i in Item join t in Transaction on i.ID equal t.ID select t).select(x => x.Sold_Price).LastOrDefault().toList();

解决方法

如果您不在EF / EF Core中使用关系，这将是我的方法

migrating hmac-auth on database 'kong'...
hmac-auth migrated up to: 000_base_hmac_auth (executed)
hmac-auth migrated up to: 002_130_to_140 (executed)
hmac-auth migrated up to: 003_200_to_210 (executed)
migrating oauth2 on database 'kong'...
oauth2 migrated up to: 000_base_oauth2 (executed)
oauth2 migrated up to: 003_130_to_140 (executed)
oauth2 migrated up to: 004_200_to_210 (executed)
oauth2 migrated up to: 005_210_to_211 (executed)
migrating ip-restriction on database 'kong'...
ip-restriction migrated up to: 001_200_to_210 (executed)
migrating jwt on database 'kong'...
jwt migrated up to: 000_base_jwt (executed)
jwt migrated up to: 002_130_to_140 (executed)
jwt migrated up to: 003_200_to_210 (executed)
migrating basic-auth on database 'kong'...
basic-auth migrated up to: 000_base_basic_auth (executed)
basic-auth migrated up to: 002_130_to_140 (executed)
basic-auth migrated up to: 003_200_to_210 (executed)
migrating key-auth on database 'kong'...
key-auth migrated up to: 000_base_key_auth (executed)
key-auth migrated up to: 002_130_to_140 (executed)
key-auth migrated up to: 003_200_to_210 (executed)
migrating session on database 'kong'...
session migrated up to: 000_base_session (executed)
migrating acl on database 'kong'...
acl migrated up to: 000_base_acl (executed)
acl migrated up to: 002_130_to_140 (executed)
acl migrated up to: 003_200_to_210 (executed)
acl migrated up to: 004_212_to_213 (executed)
migrating response-ratelimiting on database 'kong'...
response-ratelimiting migrated up to: 000_base_response_rate_limiting (executed)
migrating bot-detection on database 'kong'...
bot-detection migrated up to: 001_200_to_210 (executed)
migrating acme on database 'kong'...
acme migrated up to: 000_base_acme (executed)
38 migrations processed
38 executed
Database is up-to-date

C:\Users\donhuvy>docker run -d --name kong --network=kong-net -e "KONG_DATABASE=postgres" -e "KONG_PG_HOST=kong-database" -e "KONG_PG_USER=kong" -e "KONG_PG_PASSWORD=kong" -e "KONG_CASSANDRA_CONTACT_POINTS=kong-database" -e "KONG_PROXY_ACCESS_LOG=/dev/stdout" -e "KONG_ADMIN_ACCESS_LOG=/dev/stdout" -e "KONG_PROXY_ERROR_LOG=/dev/stderr" -e "KONG_ADMIN_ERROR_LOG=/dev/stderr" -e "KONG_ADMIN_LISTEN=0.0.0.0:8001,0.0.0.0:8444 ssl" -p 8000:8000 -p 8443:8443 -p 127.0.0.1:8001:8001 -p 127.0.0.1:8444:8444 kong:latest
docker: Error response from daemon: Conflict. The container name "/kong" is already in use by container "1326822f2bfefe7b5f5ab76ef630c83127eb7e5661929009c6c0187c0be711ed". You have to remove (or rename) that container to be able to reuse that name.
See 'docker run --help'.

C:\Users\donhuvy>

在//items = items table //transactions = transactions table var results = items.Join( transactions,item => item.Id,transaction => transaction.Id,(item,transaction) => new { ItemTransactionId = item.Id,Name = item.Item_Name,Price = transaction.Sold_Price,Date = transaction.Sold_Date }).GroupBy(x => x.ItemTransactionId) .Select(x => new { ResultDesired = x.Select(r => r.Name).FirstOrDefault() + " was sold at " + x.Select(r => new {TransactionPrice = r.Price,Date = r.Date}) .OrderByDescending(ex => ex.Date).First().TransactionPrice }).ToList(); 表之后，我将joining项/事务ID，然后根据日期重新排列