如何将以下 SQL 转换为 Linq？

Question

我正在使用 IQueryable 接口。

如何将以下 sql 语句转换为 IQueryable？

select * from customer
where joindate > DateTime.Now and
      (customertype = 'system' or customerstatus = 'active') and
      customerlocation = 'europe'

Answer 1

像这样的事情：

    var result = from record in context.customer 
    where record.joindate > DateTime.Now && 
        (record.customertype == "system" || record.customerstatus == "active") && 
        record.customerlocation == "europe"
    select record

有一个很好的工具，Linqer，它可以帮助您将 SQL 查询转换为 LINQ。当然，对于这种简单的情况来说，这有点过分了，但是如果您更熟悉 SQL，那么您当然可以考虑在繁重的查询中使用它。

您可以在这里找到它 LINQER。

Answer 2

var query = 
from i in db.customer
where i.joindate > DateTime.Now 
&& (i.customertype == 'system' || i.customerstatus == 'active')
&& i.customerlocation == 'europe'
select i;

Answer 3

var now = DateTime.Now;
var queryable = Customers.Where(x=>x.joindate > now && (x.customertype == "system" || x.customerstatus == "active") && x.customerlocation == "europe")

我不记得 linq 是否会计算 DateTime.Now 所以我只是提前将其放入变量中。

Answer 4

我更喜欢以下语法，但您也可以使用查询语法：

var results = yourContext.Customers.Where(c => (c.JoinDate > DateTime.Now) &&
    ((c.CustomerType.Equals("system") || (c.CustomerType.Equals("active")) &&
    (c.CustomerLocation.Equals("europe")));

使用查询语法：

var results = from c in yourContext.Customers
    where (c.JoinDate > DateTime.Now) &&
    (c.CustomerType.Equals("system") || c.CustomerStatus.Equals("active")) &&
    c.CustomerLocation.Equals("europe")
    select c;  

Answer 5

var result = (from c in customer
              where (c.joindate > DateTime.Now) &&
                    (c.customertype == "system" || c.customerstatus == "active") &&
                    (c.customerlocation == "europe")
              select c)
             .ToList();