FluentMongo突然引发错误 [英] FluentMongo throwing error all of a sudden

问题描述

我正在使用FluentMongo和MongoDBCSharpDriver.我的代码可以正常工作一段时间，但是在更新MongoCSharpDriver之后，当我尝试查询数据库时，我现在不断出现此错误:

I am using FluentMongo and the MongoDBCSharpDriver. My code was working fine for a while, but after updating my MongoCSharpDriver, I now I keep getting this error when I try to query the database:

鉴别器只能为类注册，不能为接口MyLib.Services.IRepoData注册."

"Discriminators can only be registered for classes, not for interface MyLib.Services.IRepoData."

接口IRepoData只是我用于保存到MongoDB的所有对象的接口.它只是为所有内容定义_id.这是断行:

The interface IRepoData is just one that I use for all my objects saved to MongoDB. It just defines _id for everything. Here is the line that is breaking:

var item = Collection.AsQueryable().SingleOrDefault(a => a.Id == itemID);

有人可以阐明这一点吗?如果我只使用没有lambda的.SingleOrDefault()，那么它可以正常工作，它会传递一个破坏它的lambda.

Can anyone shed some light on this one? If I just use .SingleOrDefault() with no lambda then it works fine, its passing a lambda that breaks it.

编辑

以防万一...

var Collection = GetCollection<MyClass>();

private MongoCollection<T> GetCollection<T>() where T : class, new()
{
    string typeName = typeof(T).Name;
    var collection = db.GetCollection<T>(typeName, safeMode);
    return collection;
}

推荐答案

找到了！我从另一个通用方法中调用GetCollection()，如下所示:

Found it! I was calling GetCollection() from within another generic method, like this:

public T Save<T>(T item) where T : class, IRepoData, new()
{
    GetCollection<T>().Save(item);
}

这导致GetCollection将T视为接口，而不是实际的实例类. GetCollection在其他任何地方都可以正常工作.

This caused GetCollection to see T as the interface instead of the actual instance class. GetCollection works fine anywhere else.

对于其他有此问题的人，我只使用了这样的低级查询... Collection.FindOneAs<T>(Query.EQ("Id", itemID.ToString()));

For anyone else with this problem, I just used a low level query like this instead... Collection.FindOneAs<T>(Query.EQ("Id", itemID.ToString()));

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