[MongoDB .NET Driver] Find & FindAsync sample

Driver & Environment & Initialization & Mapping Class

請參考
[MongoDB .NET Driver] Indexes.CreateOneAsync sample

Single Filter

假設已知PersonId
查詢此Member資料寫法如下

var filter = Builders<Member>.Filter.Eq<string>(m => m.PersonId, id);
var member = db.GetCollection<Member>(colName).Find(filter).FirstOrDefaultAsync().Result;

Projection

同上範例
但是查詢結果只需要此Member的Phone資料寫法如下

var filter = Builders<Member>.Filter.Eq<string>(m => m.PersonId, id);
// 預設會傳回_id欄位, 所以排除掉
var projection = Builders<Member>.Projection.Exclude(m => m.Id).Include(m => m.Phone);
var doc = db.GetCollection<Member>(colName).Find(filter).Project(projection).FirstOrDefaultAsync().Result;
var phone = BsonSerializer.Deserialize<string>(doc.Values.ElementAt(0).ToJson());

Compose Filter

假設需要查詢某地區特定性別的Member們
每次批次取得5000筆
寫法如下

var builder = Builders<Member>.Filter;
var filters = new List<FilterDefinition<Member>>();

filters.Add(builder.Eq(m => m.ZipCode, zipCode));
filters.Add(builder.Eq(m => m.Gender, gender));

IAsyncCursor<Member> cursor = db.GetCollection<Member>(colName).FindAsync(builder.And(filters), new FindOptions<Member>() { BatchSize = 5000 }).Result;

List<Member> members = new List<Member>();
while (cursor.MoveNextAsync().Result)
{
    members.AddRange(cursor.Current);
}