c# - LINQ 表达式包含对与不同上下文关联的查询的引用

Question

这是我的代码:

var myStrings = (from x in db1.MyStrings.Where(x => homeStrings.Contains(x.Content))
                    join y in db2.MyStaticStringTranslations on x.Id equals y.id
                    select new MyStringModel()
                    {
                        Id = x.Id,
                        Original = x.Content,
                        Translation = y.translation
                    }).ToList();

而且我收到错误消息，指出指定的 LINQ 表达式包含对与不同上下文关联的查询的引用。我知道问题在于我尝试从 db1 和 db2 访问表，但我该如何解决这个问题？

Answer 1

MyStrings is a small table

在内存中加载过滤后的 MyStrings，然后使用 LINQ 加入 MyStaticStringTranslations:

// Read the small table into memory, and make a dictionary from it.
// The last step will use this dictionary for joining.
var byId = db1.MyStrings
    .Where(x => homeStrings.Contains(x.Content))
    .ToDictionary(s => s.Id);
// Extract the keys. We will need them to filter the big table
var ids = byId.Keys.ToList();
// Bring in only the relevant records
var myStrings = db2.MyStaticStringTranslations
    .Where(y => ids.Contains(y.id))
    .AsEnumerable() // Make sure the joining is done in memory
    .Select(y => new {
        Id = y.id
        // Use y.id to look up the content from the dictionary
    ,   Original = byId[y.id].Content
    ,   Translation = y.translation
    });