使用C＃创建MongoDB唯一键

我与MongoDB共计n00b，我正在努力创建一个独特的字段EmailAddress 。 我已经在论坛上看到我必须创建一个索引，但到目前为止它对我来说都没有用。 有没有人有代码示例？ 我是否必须在每次保存/调用时创建索引，还是只创建一次？

我试过这段代码：

 DB.GetCollection(Dbname) .EnsureIndex(new IndexKeysBuilder() .Ascending("EmailAddress"), IndexOptions.SetUnique(true)); DB.GetCollection(Dbname).Save(user, SafeMode.True); 

我的User模型如下所示：

 public class User { [Required(ErrorMessage = "Email Required")] public string EmailAddress { get; set; } public ObjectId Id { get; set; } public string FirstName { get; set; } public string LastName { get; set; } } 

Answer 1

只需创建一次唯一索引，之后包含重复电子邮件地址的任何文档插入都将失败。 这是一个例子：

 var server = MongoServer.Create("mongodb://localhost"); var db = server.GetDatabase("myapp"); var users = db.GetCollection("users"); users.EnsureIndex(new IndexKeysBuilder() .Ascending("EmailAddress"), IndexOptions.SetUnique(true)); var user1 = new User { EmailAddress = "[e-mail]" }; var user2 = new User { EmailAddress = "[e-mail]" }; try { users.Save(user1, WriteConcern.Acknowledged); users.Save(user2, WriteConcern.Acknowledged); // <-- throws MongoSafeModeException } catch (MongoSafeModeException ex) { Console.WriteLine(ex.Message); } 

Answer 2

根据C＃mongo驱动程序2.0版规范，不推荐使用EnsureIndex（）： http ： //api.mongodb.org/csharp/current/html/M_MongoDB_Driver_MongoCollection_EnsureIndex_2.htm

inheritance人如何做异步和通过2.0代码：

 var mongoClient = new MongoClient("connection"); var db = mongoClient.GetDatabase("database"); var options = new CreateIndexOptions() { Unique = true }; var field = new StringFieldDefinition("EmailAddress"); var indexDefinition = new IndexKeysDefinitionBuilder().Ascending(field); await db.GetCollection("users").Indexes.CreateOneAsync(indexDefinition, options); 

Answer 3

你的代码看起来正确。 这是一个完整运行的程序供您比较：

 using System; using System.Collections.Generic; using System.Linq; using System.Text; using MongoDB.Bson; using MongoDB.Driver; using MongoDB.Driver.Builders; namespace TestEnsureIndexOnEmailAddress { public class User { public ObjectId Id; public string FirstName; public string LastName; public string EmailAddress; } public static class Program { public static void Main(string[] args) { var server = MongoServer.Create("mongodb://localhost/?safe=true"); var database = server["test"]; var users = database.GetCollection("users"); if (users.Exists()) { users.Drop(); } users.EnsureIndex(IndexKeys.Ascending("EmailAddress"), IndexOptions.SetUnique(true)); var john = new User { FirstName = "John", LastName = "Smith", EmailAddress = "[e-mail]" }; users.Insert(john); var joe = new User { FirstName = "Joe", LastName = "Smith", EmailAddress = "[e-mail]" }; users.Insert(joe); // should throw exception } } } 

您还可以使用mongo shell来确认索引是否已创建：

 > db.users.getIndexes() [ { "name" : "_id_", "ns" : "test.users", "key" : { "_id" : 1 }, "v" : 0 }, { "_id" : ObjectId("4de8152ee447ad2550e3b5fd"), "name" : "EmailAddress_1", "ns" : "test.users", "key" : { "EmailAddress" : 1 }, "unique" : true, "v" : 0 } ] >