EF Core 更新 ...从选择 WHERE

Question

如何使用 EF Core SqlServer 生成此查询？

UPDATE Table1
SET Field1 = sil.Field1,
    Field2 = sil.Field2
FROM Table2 sil WITH (NOLOCK)
WHERE sil.Field3= ''
    AND sil.Id1 = Table1.Id1
    AND sil.Id2 = Table1.Id2
    AND sil.Id3 != Table1.Id3

重要！

我想用 single 查询生成它（不是每行查询）

Answer 1

AFAIK 没有直接等同于 EF 中的 UPDATE ... FROM 语句。相反，您将查询您的数据集，更新实体模型，然后将更新推送回来。

//  2 database select statements
var table1 = database.Table1.ToList();
var table2 = database.Table2.ToList();

//  in-memory processing.  no database involvement.
foreach(Entity1 t1record in table1) {
    var t2record = table2.Where(sil => ...).FirstOrDefault();
    if(null == t2record) { continue; }
    t1record.Field1 = t2record.Field1; // etc...
}
// push changes back to the database.  EFCore should do this as a single SQL statement
database.SaveChanges();