[MongoDB .NET Driver] Indexes.CreateOneAsync sample

##2.0 .NET Driver
the driver is 100% async down to the lowest level
根據官網說明
底層100%實作async的方法

##Environment Version

• .NET 4.5

• MongoDB 3.0

##Initialization

var client = new MongoClient(connectionString);
var db = client.GetDatabase(databaseName);

##Mapping Class
假設Collection是用來儲存會員資料
Mapping Class設計如下

public class Member 
{
    public ObjectId Id { get; set; }

    public string PersonId { get; set; }

    public string Name { get; set; }

    public int Gender { get; set; }

    public string Phone { get; set; }

    public int ZipCode { get; set; }

    public string Address { get; set; }
}

##Single Index
假設查詢PersonId次數很頻繁
則可以對PersonId建立升冪¹的index

var singleIndex = await db.GetCollection<Member>(colName).Indexes.CreateOneAsync(Builders<Member>.IndexKeys.Ascending(_ => _.PersonId)).ConfigureAwait(continueOnCapturedContext: false);

##Combine Index
假設需要查詢某地區特定性別的會員
則可以對Gender及ZipCode建立升冪¹的複合index

var combineIndex = await db.GetCollection<Member>(colName).Indexes.CreateOneAsync(Builders<TaMember>.IndexKeys.Combine(
    Builders<Member>.IndexKeys.Ascending(_ => _.Gender),
    Builders<Member>.IndexKeys.Ascending(_ => _.ZipCode))).ConfigureAwait(continueOnCapturedContext: false);

1. 降冪則改寫為IndexKeys.Descending即可 ↩ ↩²