.Net Web API 006 Controller上传大文件

1、上传大文件的方式

上传大文件就需要一段一段的上传，主要是先在客户端获取文件的大小，例如想一次传256kb，那就按照256kb分割。分割后又两种上传方式。

（1）逐个数据段读取，然后调用API上传，把数据追加到文件上。上传完这一段，接着传下一段，直到上传完毕。

(资料图)

（2）方式与（1）类似，只是可以好几段可以并行上传，上传后，会把每段按照索引命名，在服务器上保存成临时文件。判断都上传完毕后，再调用合并命令，把这些小的碎文件，合并成大的目标文件。

我一般喜欢用第一种方式，主要是因为简单明了。缺点就是，因为必须等上一段完成后，再传下一段，所以无法并行上传，导致速度会受到影响。

但我参与的项目基本上都是在局域网运行并且使用人数有限，所以这种传大文件的方式是可以满足系统要求。

2、上传大文件API实现

下面的实现用到了定义的AttachedFileEntity和HttpClientEx，这两个类的定义可参考 005 Controller上传小文件。

分三步，开始上传、循环上传二进制段、结束上传。

开始上传API的目的是为了获取文件在服务器上的存储路径，代码如下。

/// 
/// 开始大上传文件/// 
/// [HttpPost][Route("StartUploadBigFile")]public IActionResult StartUploadBigFile(AttachedFileEntity pEntity, string pFileEx){    string myServerFilePath = DateTime.Now.ToString("yyyy_MM_dd") + "\\" + Guid.NewGuid().ToString() + pFileEx;    pEntity.ServerPath = myServerFilePath;    return this.Ok(pEntity);}

分段上传文件，接收到后，追加到现有的文件上。

/// 
/// 上传大文件/// 
/// /// [HttpPost][Route("UploadBigFile")][DisableRequestSizeLimit]public IActionResult UploadBigFile(string pServerPath){    var myFile = Request.Form.Files[0];    //创建目录    string myFullServerPath = AppDomain.CurrentDomain.BaseDirectory + "\\Files\\" + pServerPath;    string myFullFolder = Path.GetDirectoryName(myFullServerPath)!;    if (Directory.Exists(myFullFolder) == false)    {        Directory.CreateDirectory(myFullFolder);    }    //写入文件    Stream? myStream = null;    FileStream? myFileStream = null;    BinaryWriter? myBinaryWriter = null;    try    {        myStream = myFile.OpenReadStream();        byte[] myBytes = new byte[myStream.Length];        myStream.Read(myBytes, 0, myBytes.Length);        myStream.Seek(0, SeekOrigin.Begin);        myFileStream = new FileStream(myFullServerPath, FileMode.Append);        myBinaryWriter = new BinaryWriter(myFileStream);        myBinaryWriter.Write(myBytes);    }    catch (Exception ex)    {        return this.BadRequest("上传大文件失败," + ex.Message);    }    finally    {        myBinaryWriter?.Close();        myFileStream?.Close();        myStream?.Close();    }    return this.Ok();}

最后，结束上传，把文件的信息记录到数据库中。

/// 
/// 结束上传大文件/// 
/// [HttpPost][Route("FinishUploadBigFile")]public IActionResult FinishUploadBigFile(AttachedFileEntity pEntity){    if (string.IsNullOrEmpty(pEntity.GUID))    {        pEntity.GUID = Guid.NewGuid().ToString();    }    //记录到数据库中    //代码略    return this.Ok(pEntity);}

3、客户端调用

客户端如果用的C#，代码中没有加入进度信息，进度信息可以传入一个ProcessInfo对象，传一段数据后，就更新下进度信息。

调用的代码入下所示。

private void Init_BigFileUpLoad_UIs(){    this.UI_BigFile_Button.Click += (x, y) =>    {        var myOpenFileDialog = new OpenFileDialog        {            Filter = ".*|*.*"        };        var myIsOK = myOpenFileDialog.ShowDialog();        if (myIsOK != true)        {            return;        }        this.UI_BigFile_TextBox.Text = myOpenFileDialog.FileName;    };    this.UI_BigFileUpLoad_Button.Click += async (x, y) =>    {        var myFilePath = this.UI_BigFile_TextBox.Text.Trim();        if (myFilePath.Length == 0)        {            MessageBox.Show("请选择一个文件。");            return;        }        if (File.Exists(myFilePath) == false)        {            MessageBox.Show("文件不存在，请重新选择。");            return;        }        //定义AttachedFileEntity        var myFileEntity = new AttachedFileEntity()        {            GUID = Guid.NewGuid().ToString(),            Name = "用户头像",            KeyWord = "UserProfilePhoto",            Description = "",            EntityGUID = "AAAA"        };        //打开上传的文件        var myFileStream = new FileStream(myFilePath, FileMode.Open);        myFileEntity.FileSize = (int)myFileStream.Length;        var myFileName = Path.GetFileName(myFilePath);        //每次上传256kb        int myChunkSize = 1024 * 256;        int myChunkCount = (int)Math.Ceiling(myFileStream.Length / (double)myChunkSize);        //调用开始上传        var myHttpClient = new HttpClient();        var myHttpClientEx = new HttpClientEx(myHttpClient)        {            Url = "http://localhost:5000/api/AttachedFile/StartUploadBigFile",            HttpContent = JsonContent.Create(myFileEntity)        };        myHttpClientEx.ParameterDictionary.Add("pFileEx", Path.GetExtension(myFileName));        await myHttpClientEx.PostAsync();        if (myHttpClientEx.IsSuccess == false)        {            myFileStream.Close();            MessageBox.Show("上传文件失败，" + myHttpClientEx.ResponseContenString);            return;        }        myFileEntity = myHttpClientEx.GetResponseObject();        if (myFileEntity == null)        {            myFileStream.Close();            MessageBox.Show("上传文件失败，返回的AttachedFileEntity为null。");            return;        }        //循环上传文件        for (int i = 0; i < myChunkCount; i++)        {            //组织数据            int myByteArraySize = myChunkSize;            if (i == myChunkCount - 1)            {                myByteArraySize = (int)(myFileStream.Length % myChunkSize);            }            byte[] myBytes = new byte[myByteArraySize];            myFileStream.Position = myChunkSize * i;            myFileStream.Read(myBytes, 0, myBytes.Length);            var myMemoryStream = new MemoryStream(myBytes);            //请求服务            myHttpClientEx = new HttpClientEx(myHttpClient)            {                Url = "http://localhost:5000/api/AttachedFile/UploadBigFile",                HttpContent = new MultipartFormDataContent                    {                        {new StreamContent(myMemoryStream),"pFile",myFileName}                    }            };            myHttpClientEx.ParameterDictionary.Add("pServerPath", myFileEntity!.ServerPath);            await myHttpClientEx.PostAsync();            //解析结果            if (myHttpClientEx.IsSuccess == false)            {                myFileStream.Close();                MessageBox.Show("上传文件失败，" + myHttpClientEx.ResponseContenString);                return;            }        }        //结束上传        myHttpClientEx = new HttpClientEx(myHttpClient)        {            Url = "http://localhost:5000/api/AttachedFile/FinishUploadBigFile",            HttpContent = JsonContent.Create(myFileEntity)        };        await myHttpClientEx.PostAsync();        if (myHttpClientEx.IsSuccess == false)        {            myFileStream.Close();            MessageBox.Show("上传文件失败，" + myHttpClientEx.ResponseContenString);            return;        }        myFileStream.Close();        myFileEntity = myHttpClientEx.GetResponseObject();        var myEntityJosnString = JsonSerializer.Serialize(myFileEntity);        MessageBox.Show(myEntityJosnString);    };}

如果客户端是js，代码如下。

on(myButton, "change", function (e) {    var myFileReader = new FileReader();    var myFileName = "";    myFileReader.onloadend = function () {        var myFileResult = myFileReader.result;        var myFileLength = myFileResult.byteLength;        var myPerLength = 1024 * 256;        var myCount = Math.ceil(myFileLength / myPerLength);        var myFileEntity = new Object()        {            ServerPath: ""        };        //调用开始上传StartUploadBigFile，具体代码略。        var myK = 0;        Upload();        function Upload() {            var myByteArray = myFileResult.slice(myPerLength * myK, myPerLength * (myK + 1));            var myBlob = new Blob([myByteArray]);            var myFile = new File([myBlob], myFileName);            var myFormData = new FormData();            myFormData.append("file", myFile)            request.post(myUrl + "?pServerFile=" + myFileEntity.ServerPath +, {                data: myFormData            }).then(function (data) {                myFileEntity = json.parse(data);                myK++;                if (myK < myCount) {                    Upload();                }                else {                    alert("上传大文件结束。");                    alert(json.stringify(myFileEntity));                    //结束，post FinishUploadBigFile                 }            }, function (err) {                alert(err);                return;            });        }    }    myFileName = this.files[0].name;    myFileReader.readAsArrayBuffer(this.files[0]);});

Js代码没有实际测试，只是一个思路。

关键词：