帮助我使用实体框架从 SQL 转换为 linq 嵌套 lambda 表达式

Posted 2023-03-23

【中文标题】帮助我使用实体框架从 SQL 转换为 linq 嵌套 lambda 表达式

【英文标题】：Helpme to Convert from SQL to linq Nested lambda Expression with EntityFramework

【发布时间】：2013-01-15 21:05:14

【问题描述】：

我正在尝试从 SQL 中获取一些数据，但我无法使用 Linq 来完成，在 T-SQL 中这项工作：

select *
from MTRBatch MB
Inner Join MTR M on MB.Id = M.MTRBatchId
Inner JOIN MTRHeats MH on M.Id = MH.MTRId
LEFT OUTER JOIN Vendor V on MB.VendorId = v.Id
Inner Join Manufacturer MF on MB.ManufacturerId = MF.Id
Where MB.ManufacturerId = 1
AND MH.Heat = 'z01'

我需要除了那个过滤器之外的所有树。

我试过了，但没用：

MTRBatches
.Include(x => x.MTRs.Select(m => m.MTRHeats))
.Include(x => x.Manufacturer)
.Include(x => x.Vendor)
.Where(x => (x.Manufacturer.Id == 1));
.Where(x => x.MTRs.Any(m => m.MTRHeats.Any(h => h.Heat == 'z01')));

【问题讨论】：

没有像...那样工作？结果错误？碰撞燃烧？没有编译？

结果不正确：它给我带来了所有 MTR，就像 MH.HEat 过滤器没有发生

【参考方案1】：

这应该会有所帮助； dataContext 是您的 Entity Framework container 实例的名称。

var result = dataContext.MTRBatches
    .Join(dataContext.MTRs,
        mb => mb.Id,
        mtr => mtr.MTRBatchId,
        (mb, mtr) => new Batch = mb, MTR = mtr )
    .Join(dataContext.MTRHeats,
        x => x.MTR.Id,
        mh => mh.MTRId,
        (x, mh) => new Batch = x.Batch, MTR = x.MTR, Heat = mh )
    .Join(dataContext.Vendors.DefaultIfEmpty(),
        x => x.Batch.VendorId,
        v => v.Id,
        (x, v) => new Batch = x.Batch, MTR = x.MTR, Heat = x.Heat, Vendor = v )
    .Join(dataContext.Manufacturers,
        x => x.Batch.ManufacturerId,
        mf => mf.Id,
        (x, mf) => new Batch = x.Batch, MTR = x.MTR, Heat = x.Heat, Vendor = x.Vendor, Manufacturer = mf)
    .Where(x => x.Manufacturer.Id == 1 && x.Heat.Heat == "z01");