Question

I m new to .NET. I m trying to do something very simple. I would like to perform a search on a Model in my controller and retrieve the first entity returned :

var cercueils = from y in db.Cercueils select y;
cercueils = cercueils.Where(z => z.Type.ToUpper().Contains(dr[13].ToUpper())
          || z.AncienType.ToUpper().Contains(dr[13].ToUpper()));
Cercueil cercueil = cercueils.First();

But this is not good, as it throws an error :

Le type de nœud « ArrayIndex » de l expression LINQ n est pas pris en charge dans LINQ to Entities.

页: 1

我如何能够做到这一点?

感谢您的帮助。

Answer 1

I believe Linq doesn t know how to execute dr[13] in the context of deferred execution... try the following:

var tmp = dr[13].ToUpper();
var cercueils = from y in db.Cercueils select y;
cercueils = cercueils.Where(z => z.Type.ToUpper().Contains(tmp)
          || z.AncienType.ToUpper().Contains(tmp));
Cercueil cercueil = cercueils.FirstOrDefault();

此外,我通常建议采用“第一号命令”,随后进行无效检查:

Answer 2

我认为,Where(z =>z.Type.ToUpper(......)Contains(dr[13].ToUpper()等)不能被转至Kall类查询,因此Linq允许各实体给你上述错误。



You can fix the error in twi ways: either transform your expression so that Linq to Entities is able to generate the query (I had some success with IndexOf() instead of Contains()), or just download the entire table and perform the search locally (obviously, the second option will hamper performance):

var cercueils = (from y in db.Cercueils select y).ToList(); // load the entire dataset
cercueils = cercueils.Where(z => z.Type.ToUpper().Contains(dr[13].ToUpper())
      || z.AncienType.ToUpper().Contains(dr[13].ToUpper()));
Cercueil cercueil = cercueils.First();

Answer 3

        var cercueils = (from y in db.Cercueils
                        where y.blahblah = blahblah
                        select y).FirstOrDefault();

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