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这是情况。我插入一个新的帖子,插入后我获取帖子,它工作正常。然后我改变一个领域,并更新哪些工作正常。当我尝试在更新后获取相同的帖子时,就会出现问题。它总是返回null。C#MongoDb驱动程序问题更新失败
public class Post
{
public string _id { get; set; }
public string Title { get; set; }
public string Body { get; set; }
}
// insert a post
var post = new Post() {Title = "first post", Body = "my first post"};
var posts = _db.GetCollection("posts");
var document = post.ToDocument();
// inserts successfully!
posts.Insert(document);
// now get the post
var spec = new Document() {{"_id", document["_id"]}};
// post was found success
var persistedPost = posts.FindOne(spec).ToClass<Post>();
persistedPost.Body = "this post has been edited again!!";
var document2 = persistedPost.ToDocument();
// updates the record success although I don't want to pass the second parameter
posts.Update(document2,spec);
// displays that the post has been updated
foreach(var d in posts.FindAll().Documents)
{
Console.WriteLine(d["_id"]);
Console.WriteLine(d["Body"]);
}
// FAIL TO GET THE UPDATED POST. THIS ALWAYS RETURNS NULL ON FindOne call!
var updatedPost = posts.FindOne(new Document() {{"_id",document["_id"]}}).ToClass<Post>(); // this pulls back the old record with Body = my first post
Assert.AreEqual(updatedPost.Body,persistedPost.Body);
UPDATE:
我想我已经解决了这个问题,但这个问题是很奇怪的。看最后一行。
var updatedPost = posts.FindOne(new Document() {{"_id",document["_id"]}}).ToClass<Post>();
FindOne方法取决于文档[“_ id”]的新文档。不幸的是,这不起作用,出于某种原因,它需要您发送与更新命令后将获得的persistedPost更新关联的_id。这里是例子:
var persistedPost = posts.FindOne(spec).ToClass<Post>();
persistedPost.Body = "this is edited";
var document2 = persistedPost.ToDocument();
posts.Update(document2,new Document() {{"_id",document["_id"]}});
var updatedPost = posts.FindOne(new Document(){{"_id",document2["_id"]}}).ToClass<Post>();
Console.WriteLine(updatedPost.Body);
看到,现在我发送document2 [“_ id”]而不是文档字段。这似乎工作正常。我猜它为每个“_id”字段生成的24字节代码是不同的。