C# 玩转MongoDB（三）

前面两篇文章，已经讲解了C#对MongoDB的基本操作以及小文件的读写存储，那么对于大型（>=16M）文件呢？具体又该如何操作呢，本文主要以一个简单的小例子，简述C#如何通过GridFS进行MongoDB的大文件的操作，仅供学习分享使用，如有不足之处，还请指正。

什么是GridFS?

在实现GridFS方式前我先讲讲它的原理，为什么可以存大文件。驱动首先会在当前数据库创建两个集合："fs.files"和"fs.chunks"集合，前者记录了文件名，文件创建时间，文件类型等基本信息；后者分块存储了文件的二进制数据（并支持加密这些二进制数据）。分块的意思是把文件按照指定大小分割，然后存入多个文档中。"fs.files"怎么知道它对应的文件二进制数据在哪些块呢？那是因为在"fs.chunks"中有个"files_id"键，它对应"fs.files"的"_id"。"fs.chunks"还有一个键(int型)"n"，它表明这些块的先后顺序。这两个集合名中的"fs"也是可以通过参数自定义的。

GridFS存储原理

一个文件存储在两个集合中，一个用于存储元数据（文件名称，类型，大小等内容，可便于索引），一个用于存储真实二进制数据（分块存储），如下所示：

GridFS安装

如果需要存储大型文件，则需要安装GridFS插件，如下所示：

项目--右键--管理Nuget程序包--打卡Nuget包管理器--浏览搜索MongoDB.Driver.GridFS--安装。如下所示：

示例截图

首先是文件的查询，如下所示：

文件的新增

核心代码

本示例主要是在MongoDB中进行文件的操作，所以之前的MongoHelper已不再适用，本例新增了文件专用帮助类MongoFileHelper，如下所示：

  1 using MongoDB.Bson;
  2 using MongoDB.Driver;
  3 using MongoDB.Driver.GridFS;
  4 using System;
  5 using System.Collections.Generic;
  6 using System.IO;
  7 using System.Linq;
  8 using System.Text;
  9 using System.Threading.Tasks;
 10 
 11 namespace DemoMongo.Common
 12 {
 13 
 14     public class MongoFileHelper
 15     {
 16 
 17         private string connStr = "mongodb://127.0.0.1:27017";//服务器网址
 18 
 19         private string dbName = "hexdb";//数据库名称
 20 
 21         private IMongoClient client;//连接客户端
 22 
 23         private IMongoDatabase db;//连接数据库
 24 
 25         private string collName;//集合名称
 26 
 27         public MongoFileHelper()
 28         {
 29 
 30         }
 31 
 32         public MongoFileHelper(string connStr, string dbName, string collName)
 33         {
 34             this.connStr = connStr;
 35             this.dbName = dbName;
 36             this.collName = collName;
 37             this.Init();
 38         }
 39 
 40         /// <summary>
 41         /// 初始化连接客户端
 42         /// </summary>
 43         private void Init()
 44         {
 45             if (client == null)
 46             {
 47                 client = new MongoClient(this.connStr);
 48             }
 49             if (db == null)
 50             {
 51                 db = client.GetDatabase(this.dbName);
 52             }
 53         }
 54 
 55         /// <summary>
 56         /// 通过字节方式上传
 57         /// </summary>
 58         /// <param name="filePath"></param>
 59         public void UploadFile(string filePath)
 60         {
 61             IGridFSBucket bucket = new GridFSBucket(db);
 62             byte[] source = File.ReadAllBytes(filePath);
 63             string fileName = Path.GetFileName(filePath);
 64             var options = new GridFSUploadOptions
 65             {
 66                 ChunkSizeBytes = 64512, // 63KB
 67                 Metadata = new BsonDocument
 68                 {
 69                     { "resolution", "1080P" },
 70                     { "copyrighted", true }
 71                 }
 72             };
 73             var id = bucket.UploadFromBytes(fileName, source);
 74             //返回的ID，表示文件的唯一ID
 75 
 76 
 77         }
 78 
 79         /// <summary>
 80         /// 通过Stream方式上传
 81         /// </summary>
 82         /// <param name="filePath"></param>
 83         public void UploadFile2(string filePath)
 84         {
 85             IGridFSBucket bucket = new GridFSBucket(db);
 86             var stream = new FileStream(filePath, FileMode.Open);
 87 
 88             string fileName = Path.GetFileName(filePath);
 89             var options = new GridFSUploadOptions
 90             {
 91                 ChunkSizeBytes = 64512, // 63KB
 92                 Metadata = new BsonDocument
 93                 {
 94                     { "resolution", "1080P" },
 95                     { "copyrighted", true }
 96                 }
 97             };
 98             var id = bucket.UploadFromStream(fileName, stream);
 99             //返回的ID，表示文件的唯一ID
100 
101 
102         }
103 
104         /// <summary>
105         /// 通过字节写入到流
106         /// </summary>
107         /// <param name="filePath"></param>
108         public void UploadFile3(string filePath)
109         {
110             IGridFSBucket bucket = new GridFSBucket(db);
111             byte[] source = File.ReadAllBytes(filePath);
112             string fileName = Path.GetFileName(filePath);
113             var options = new GridFSUploadOptions
114             {
115                 ChunkSizeBytes = 64512, // 63KB
116                 Metadata = new BsonDocument
117                 {
118                     { "resolution", "1080P" },
119                     { "copyrighted", true }
120                 }
121             };
122             using (var stream = bucket.OpenUploadStream(fileName, options))
123             {
124                 var id = stream.Id;
125                 stream.Write(source, 0, source.Length);
126                 stream.Close();
127             }
128         }
129 
130         /// <summary>
131         /// 下载文件
132         /// </summary>
133         /// <param name="id"></param>
134         public void DownloadFile(ObjectId id,string filePath)
135         {
136             IGridFSBucket bucket = new GridFSBucket(db);
137             byte[] source = bucket.DownloadAsBytes(id);
138             //返回的字节内容
139             //var bytes = await bucket.DownloadAsBytesAsync(id);
140             using (Stream stream = new FileStream(filePath, FileMode.OpenOrCreate)) {
141                 stream.Write(source, 0, source.Length);
142             }
143         }
144 
145         public void DownloadFile2(ObjectId id)
146         {
147             IGridFSBucket bucket = new GridFSBucket(db);
148             Stream destination = null;
149             bucket.DownloadToStream(id, destination);
150             //返回的字节内容
151             //await bucket.DownloadToStreamAsync(id, destination);
152 
153         }
154 
155         public void DownloadFile3(ObjectId id)
156         {
157             IGridFSBucket bucket = new GridFSBucket(db);
158             Stream destination = null;
159             using (var stream = bucket.OpenDownloadStream(id))
160             {
161                 // read from stream until end of file is reached
162                 stream.Close();
163             }
164         }
165 
166         public void DownloadFile4(string fileName)
167         {
168             IGridFSBucket bucket = new GridFSBucket(db);
169             var bytes = bucket.DownloadAsBytesByName(fileName);
170 
171             // or
172 
173             Stream destination = null;
174             bucket.DownloadToStreamByName(fileName, destination);
175 
176             // or
177 
178             using (var stream = bucket.OpenDownloadStreamByName(fileName))
179             {
180                 // read from stream until end of file is reached
181                 stream.Close();
182             }
183         }
184 
185         public List<MongoFile> FindFiles()
186         {
187             IGridFSBucket bucket = new GridFSBucket(db);
188             var filter = Builders<GridFSFileInfo>.Filter.And(
189                 //Builders<GridFSFileInfo>.Filter.Eq(x => x.Filename, string.Empty),
190                 Builders<GridFSFileInfo>.Filter.Gte(x => x.UploadDateTime, new DateTime(2015, 1, 1, 0, 0, 0, DateTimeKind.Utc)),
191                 Builders<GridFSFileInfo>.Filter.Lt(x => x.UploadDateTime, new DateTime(2022, 2, 1, 0, 0, 0, DateTimeKind.Utc)));
192             var sort = Builders<GridFSFileInfo>.Sort.Descending(x => x.UploadDateTime);
193             var options = new GridFSFindOptions
194             {
195                 //Limit = 1,
196                 Sort = sort
197             };
198             List<MongoFile> lstFiles = new List<MongoFile>();
199             using (var cursor = bucket.Find(filter, options))
200             {
201                 var fileInfos = cursor.ToList();
202                 foreach (var fileInfo in fileInfos) {
203                     MongoFile f = new MongoFile()
204                     {
205                          Id=fileInfo.Id,
206                          name = fileInfo.Filename,
207                          suffix = Path.GetExtension(fileInfo.Filename),
208                         size = int.Parse(fileInfo.Length.ToString())
209                     };
210                     lstFiles.Add(f);
211                 }
212             }
213             return lstFiles;
214         }
215 
216         public List<MongoFile> FindFileByName(string fileName)
217         {
218             IGridFSBucket bucket = new GridFSBucket(db);
219             var filter = Builders<GridFSFileInfo>.Filter.And(
220                 Builders<GridFSFileInfo>.Filter.Eq(x => x.Filename, fileName),
221                 Builders<GridFSFileInfo>.Filter.Gte(x => x.UploadDateTime, new DateTime(2015, 1, 1, 0, 0, 0, DateTimeKind.Utc)),
222                 Builders<GridFSFileInfo>.Filter.Lt(x => x.UploadDateTime, new DateTime(2015, 2, 1, 0, 0, 0, DateTimeKind.Utc)));
223             var sort = Builders<GridFSFileInfo>.Sort.Descending(x => x.UploadDateTime);
224             var options = new GridFSFindOptions
225             {
226                 //Limit = 1,
227                 Sort = sort
228             };
229             List<MongoFile> lstFiles = new List<MongoFile>();
230             using (var cursor = bucket.Find(filter, options))
231             {
232                 var fileInfos = cursor.ToList();
233                 foreach (var fileInfo in fileInfos)
234                 {
235                     MongoFile f = new MongoFile()
236                     {
237                         Id = fileInfo.Id,
238                         name = fileInfo.Filename,
239                         suffix = Path.GetExtension(fileInfo.Filename),
240                         size = int.Parse(fileInfo.Length.ToString())
241                     };
242                     lstFiles.Add(f);
243                 }
244             }
245             return lstFiles;
246         }
247     }
248 }

然后操作时，调用帮助类即可，如下所示：

查询调用

 1        private void btnQuery_Click(object sender, EventArgs e)
 2         {
 3             string name = this.txtName.Text.Trim();
 4             List<MongoFile> fileInfos = new List<MongoFile>();
 5             if (string.IsNullOrEmpty(name))
 6             {
 7                 fileInfos = helper.FindFiles();
 8             }
 9             else {
10                 fileInfos = helper.FindFileByName(name);
11             }
12             
13             this.dgView.AutoGenerateColumns = false;
14             this.bsView.DataSource = fileInfos;
15             this.dgView.DataSource = this.bsView;
16         }

下载调用

 1         private void dgView_CellContentClick(object sender, DataGridViewCellEventArgs e)
 2         {
 3             if (e.ColumnIndex == 3) {
 4                 //第3个是下载按钮
 5                 SaveFileDialog sfd = new SaveFileDialog();
 6                 
 7                 var file = (MongoFile)(this.dgView.Rows[e.RowIndex].DataBoundItem);
 8                 sfd.FileName = file.name;
 9                 sfd.Title = "请保存文件";
10                 if (DialogResult.OK == sfd.ShowDialog())
11                 {
12                     helper.DownloadFile(file.Id,sfd.FileName);
13                     MessageBox.Show("保存成功");
14 
15                 }
16             }
17         }

保存调用

 1         private void btnSave_Click(object sender, EventArgs e)
 2         {
 3             string filePath = this.txtPath.Text;
 4             if (!string.IsNullOrEmpty(filePath))
 5             {
 6                 this.helper.UploadFile(filePath);
 7                 MessageBox.Show("保存成功");
 8             }
 9             else {
10                 MessageBox.Show("请先选择文件");
11             }
12             
13         }