下面是我的工作示例：

[HttpPost]
    [ValidateAntiForgeryToken]
    public async Task<ActionResult> Create(Product product, HttpPostedFileBase file)
    {
        if (!ModelState.IsValid)
            return PartialView("Create", product);
        if (file != null)
        {

            var fileName = Path.GetFileName(file.FileName);
            var guid = Guid.NewGuid().ToString();
            var path = Path.Combine(Server.MapPath("~/Content/Uploads/ProductImages"), guid + fileName);
            file.SaveAs(path);
            string fl = path.Substring(path.LastIndexOf("\\"));
            string[] split = fl.Split('\\');
            string newpath = split[1];
            string imagepath = "Content/Uploads/ProductImages/" + newpath;
            using (MemoryStream ms = new MemoryStream())
            {
                file.InputStream.CopyTo(ms);
                byte[] array = ms.GetBuffer();
            }
            var nId = Guid.NewGuid().ToString();
            // Save record to database
            product.Id = nId;
            product.State = 1;
            product.ImagePath = imagepath;
            product.CreatedAt = DateTime.Now;
            db.Products.Add(product);
            await db.SaveChangesAsync();
            TempData["message"] = "ProductCreated";

            //return RedirectToAction("Index", product);
        }
        // after successfully uploading redirect the user
        return Json(new { success = true });
    }

要传输到字节[]（例如，用于保存到DB）：

using (MemoryStream ms = new MemoryStream()) {
    file.InputStream.CopyTo(ms);
    byte[] array = ms.GetBuffer();
}

若要将输入流直接传输到数据库中，而不将其存储在内存中，您可以使用从此处获取的此类，并稍作更改：

public class VarbinaryStream : Stream {
private SqlConnection _Connection;

private string _TableName;
private string _BinaryColumn;
private string _KeyColumn;
private int _KeyValue;

private long _Offset;

private SqlDataReader _SQLReader;
private long _SQLReadPosition;

private bool _AllowedToRead = false;

public VarbinaryStream(
    string ConnectionString,
    string TableName,
    string BinaryColumn,
    string KeyColumn,
    int KeyValue,
    bool AllowRead = false)
{
  // create own connection with the connection string.
  _Connection = new SqlConnection(ConnectionString);

  _TableName = TableName;
  _BinaryColumn = BinaryColumn;
  _KeyColumn = KeyColumn;
  _KeyValue = KeyValue;


  // only query the database for a result if we are going to be reading, otherwise skip.
  _AllowedToRead = AllowRead;
  if (_AllowedToRead == true)
  {
    try
    {
      if (_Connection.State != ConnectionState.Open)
        _Connection.Open();

      SqlCommand cmd = new SqlCommand(
                      @"SELECT TOP 1 [" + _BinaryColumn + @"]
                            FROM [dbo].[" + _TableName + @"]
                            WHERE [" + _KeyColumn + "] = @id",
                  _Connection);

      cmd.Parameters.Add(new SqlParameter("@id", _KeyValue));

      _SQLReader = cmd.ExecuteReader(
          CommandBehavior.SequentialAccess |
          CommandBehavior.SingleResult |
          CommandBehavior.SingleRow |
          CommandBehavior.CloseConnection);

      _SQLReader.Read();
    }
    catch (Exception e)
    {
      // log errors here
    }
  }
}

// this method will be called as part of the Stream ímplementation when we try to write to our VarbinaryStream class.
public override void Write(byte[] buffer, int index, int count)
{
  try
  {
    if (_Connection.State != ConnectionState.Open)
      _Connection.Open();

    if (_Offset == 0)
    {
      // for the first write we just send the bytes to the Column
      SqlCommand cmd = new SqlCommand(
                                  @"UPDATE [dbo].[" + _TableName + @"]
                                            SET [" + _BinaryColumn + @"] = @firstchunk 
                                        WHERE [" + _KeyColumn + "] = @id",
                              _Connection);

      cmd.Parameters.Add(new SqlParameter("@firstchunk", buffer));
      cmd.Parameters.Add(new SqlParameter("@id", _KeyValue));

      cmd.ExecuteNonQuery();

      _Offset = count;
    }
    else
    {
      // for all updates after the first one we use the TSQL command .WRITE() to append the data in the database
      SqlCommand cmd = new SqlCommand(
                              @"UPDATE [dbo].[" + _TableName + @"]
                                        SET [" + _BinaryColumn + @"].WRITE(@chunk, NULL, @length)
                                    WHERE [" + _KeyColumn + "] = @id",
                           _Connection);

      cmd.Parameters.Add(new SqlParameter("@chunk", buffer));
      cmd.Parameters.Add(new SqlParameter("@length", count));
      cmd.Parameters.Add(new SqlParameter("@id", _KeyValue));

      cmd.ExecuteNonQuery();

      _Offset += count;
    }
  }
  catch (Exception e)
  {
    // log errors here
  }
}

// this method will be called as part of the Stream ímplementation when we try to read from our VarbinaryStream class.
public override int Read(byte[] buffer, int offset, int count)
{
  try
  {
    long bytesRead = _SQLReader.GetBytes(0, _SQLReadPosition, buffer, offset, count);
    _SQLReadPosition += bytesRead;
    return (int)bytesRead;
  }
  catch (Exception e)
  {
    // log errors here
  }
  return -1;
}
public override bool CanRead
{
  get { return _AllowedToRead; }
}

protected override void Dispose(bool disposing)
{
  if (_Connection != null)
  {
    if (_Connection.State != ConnectionState.Closed)
      try { _Connection.Close();           }
      catch { }
    _Connection.Dispose();
  }
  base.Dispose(disposing);
}

#region unimplemented methods
public override bool CanSeek
{
  get { return false; }
}

public override bool CanWrite
{
  get { return true; }
}

public override void Flush()
{
  throw new NotImplementedException();
}

public override long Length
{
  get { throw new NotImplementedException(); }
}

public override long Position
{
  get
  {
    throw new NotImplementedException();
  }
  set
  {
    throw new NotImplementedException();
  }
}
public override long Seek(long offset, SeekOrigin origin)
{
  throw new NotImplementedException();
}

public override void SetLength(long value)
{
  throw new NotImplementedException();
}
#endregion unimplemented methods  }

以及用法：

  using (var filestream = new VarbinaryStream(
                            "Connection_String",
                            "Table_Name",
                            "Varbinary_Column_name",
                            "Key_Column_Name",
                            keyValueId,
                            true))
  {
    postedFile.InputStream.CopyTo(filestream);
  }

另一种传输到字节[]的方法（用于保存到DB）。

@Arthur的方法工作得很好，但不能完美复制，因此MS Office文档在从数据库检索后可能无法打开。MemoryStream.GetBuffer（）可以在字节[]的末尾返回额外的空字节，但可以使用MemoryStream.ToArray（）来解决这个问题。然而，我发现这个替代方案可以完美地适用于所有文件类型：

using (var binaryReader = new BinaryReader(file.InputStream))
{
    byte[] array = binaryReader.ReadBytes(file.ContentLength);
}

这是我的完整代码：

文档类别：

public class Document
{
    public int? DocumentID { get; set; }
    public string FileName { get; set; }
    public byte[] Data { get; set; }
    public string ContentType { get; set; }
    public int? ContentLength { get; set; }

    public Document()
    {
        DocumentID = 0;
        FileName = "New File";
        Data = new byte[] { };
        ContentType = "";
        ContentLength = 0;
    }
}

文件下载：

[HttpGet]
public ActionResult GetDocument(int? documentID)
{
    // Get document from database
    var doc = dataLayer.GetDocument(documentID);

    // Convert to ContentDisposition
    var cd = new System.Net.Mime.ContentDisposition
    {
        FileName = doc.FileName, 

        // Prompt the user for downloading; set to true if you want 
        // the browser to try to show the file 'inline' (display in-browser
        // without prompting to download file).  Set to false if you 
        // want to always prompt them to download the file.
        Inline = true, 
    };
    Response.AppendHeader("Content-Disposition", cd.ToString());

    // View document
    return File(doc.Data, doc.ContentType);
}

文件上载：

[HttpPost]
public ActionResult GetDocument(HttpPostedFileBase file)
{
    // Verify that the user selected a file
    if (file != null && file.ContentLength > 0)
    {
        // Get file info
        var fileName = Path.GetFileName(file.FileName);
        var contentLength = file.ContentLength;
        var contentType = file.ContentType;

        // Get file data
        byte[] data = new byte[] { };
        using (var binaryReader = new BinaryReader(file.InputStream))
        {
            data = binaryReader.ReadBytes(file.ContentLength);
        }

        // Save to database
        Document doc = new Document()
        {
            FileName = fileName,
            Data = data,
            ContentType = contentType,
            ContentLength = contentLength,
        };
        dataLayer.SaveDocument(doc);

        // Show success ...
        return RedirectToAction("Index");
    }
    else
    {
        // Show error ...
        return View("Foo");
    }
}

视图（代码段）：

@using (Html.BeginForm("GetDocument", "Home", FormMethod.Post, new { enctype = "multipart/form-data" }))
{
    <input type="file" name="file" />
    <input type="submit" value="Upload File" />
}

如果你碰巧像我一样在这里跌跌撞撞，想知道尽管代码正确，为什么你的代码仍然不工作。然后，请在输入控件中查找name属性，您可能会意外错过或从未将其放在首位。

<input class="custom-file-input" name="UploadFile" id="UploadFile" type="file" onchange="ValidateFile(this);" accept=".xls, .xlsx">
                             

我在做文件上传概念时也遇到过同样的错误。我知道开发人员为这个问题提供了很多答案。

尽管我回答这个问题的原因是，由于下面提到的疏忽错误，我犯了这个错误。

<input type="file" name="uploadedFile" />

在指定name属性时，请确保控制器参数也具有相同的名称值“uploadedFile”。这样地：

   [HttpPost]
            public ActionResult FileUpload(HttpPostedFileBase uploadedFile)
            {

            }

否则它不会被映射。

您不使用文件输入控件。ASP.NET MVC中未使用服务器端控件。查看下面的博客文章，其中说明了如何在ASP.NET MVC中实现这一点。

因此，您将首先创建一个HTML表单，其中包含文件输入：

@using (Html.BeginForm("Index", "Home", FormMethod.Post, new { enctype = "multipart/form-data" }))
{
    <input type="file" name="file" />
    <input type="submit" value="OK" />
}

然后你会有一个控制器来处理上传：

public class HomeController : Controller
{
    // This action renders the form
    public ActionResult Index()
    {
        return View();
    }

    // This action handles the form POST and the upload
    [HttpPost]
    public ActionResult Index(HttpPostedFileBase file)
    {
        // Verify that the user selected a file
        if (file != null && file.ContentLength > 0) 
        {
            // extract only the filename
            var fileName = Path.GetFileName(file.FileName);
            // store the file inside ~/App_Data/uploads folder
            var path = Path.Combine(Server.MapPath("~/App_Data/uploads"), fileName);
            file.SaveAs(path);
        }
        // redirect back to the index action to show the form once again
        return RedirectToAction("Index");        
    }
}