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");        
    }
}

通常，您还希望传递一个视图模型，而不仅仅是一个文件。在下面的代码中，您将发现一些其他有用的功能：

检查文件是否已附加检查文件大小是否为0检查文件大小是否大于4 MB检查文件大小是否小于100字节检查文件扩展名

可以通过以下代码完成：

[HttpPost]
public ActionResult Index(MyViewModel viewModel)
{
    // if file's content length is zero or no files submitted

    if (Request.Files.Count != 1 || Request.Files[0].ContentLength == 0)
    {
        ModelState.AddModelError("uploadError", "File's length is zero, or no files found");
        return View(viewModel);
    }

    // check the file size (max 4 Mb)

    if (Request.Files[0].ContentLength > 1024 * 1024 * 4)
    {
        ModelState.AddModelError("uploadError", "File size can't exceed 4 MB");
        return View(viewModel);
    }

    // check the file size (min 100 bytes)

    if (Request.Files[0].ContentLength < 100)
    {
        ModelState.AddModelError("uploadError", "File size is too small");
        return View(viewModel);
    }

    // check file extension

    string extension = Path.GetExtension(Request.Files[0].FileName).ToLower();

    if (extension != ".pdf" && extension != ".doc" && extension != ".docx" && extension != ".rtf" && extension != ".txt")
    {
        ModelState.AddModelError("uploadError", "Supported file extensions: pdf, doc, docx, rtf, txt");
        return View(viewModel);
    }

    // extract only the filename
    var fileName = Path.GetFileName(Request.Files[0].FileName);

    // store the file inside ~/App_Data/uploads folder
    var path = Path.Combine(Server.MapPath("~/App_Data/uploads"), fileName);

    try
    {
        if (System.IO.File.Exists(path))
            System.IO.File.Delete(path);

        Request.Files[0].SaveAs(path);
    }
    catch (Exception)
    {
        ModelState.AddModelError("uploadError", "Can't save file to disk");
    }

    if(ModelState.IsValid)
    {
        // put your logic here

        return View("Success");
    }

    return View(viewModel);         
}

确保你有

@Html.ValidationMessage("uploadError")

在您的视图中查看验证错误。

还要记住，默认最大请求长度为4MB（maxRequestLength=4096），要上载更大的文件，必须在web.config中更改此参数：

<system.web>
    <httpRuntime maxRequestLength="40960" executionTimeout="1100" />

（此处40960=40 MB）。

执行超时是秒的整数。您可能希望将其更改为允许上传大量文件。

提供完整的解决方案

首先在MVC视图中使用.CShtml中的输入

<input type="file" id="UploadImg" /></br>
<img id="imgPreview" height="200" width="200" />

现在调用Ajax调用

  $("#UploadImg").change(function () {
    var data = new FormData();
    var files = $("#UploadImg").get(0).files;
    if (files.length > 0) {
        data.append("MyImages", files[0]);
    }

    $.ajax({
        // url: "Controller/ActionMethod"
        url: "/SignUp/UploadFile",
        type: "POST",
        processData: false,
        contentType: false,
        data: data,
        success: function (response)
        {
            //code after success
            $("#UploadPhoto").val(response);
            $("#imgPreview").attr('src', '/Upload/' + response);
        },
        error: function (er) {
            //alert(er);
        }

    });
});

控制器Json呼叫

[HttpGet]
public JsonResult UploadFile()
    {
        string _imgname = string.Empty;
        if (System.Web.HttpContext.Current.Request.Files.AllKeys.Any())
        {
            var pic = System.Web.HttpContext.Current.Request.Files["MyImages"];
            if (pic.ContentLength > 0)
            {
                var fileName = Path.GetFileName(pic.FileName);
                var _ext = Path.GetExtension(pic.FileName);

                _imgname = Guid.NewGuid().ToString();
                var _comPath = Server.MapPath("/MyFolder") + _imgname + _ext;
                _imgname = "img_" + _imgname + _ext;

                ViewBag.Msg = _comPath;
                var path = _comPath;
                tblAssignment assign = new tblAssignment();
                assign.Uploaded_Path = "/MyFolder" + _imgname + _ext;
                // Saving Image in Original Mode
                pic.SaveAs(path);
            }
        }
        return Json(Convert.ToString(_imgname), JsonRequestBehavior.AllowGet);
    }

使用formdata上载文件

.cshtml文件

     var files = $("#file").get(0).files;
     if (files.length > 0) {
                data.append("filekey", files[0]);}


   $.ajax({
            url: '@Url.Action("ActionName", "ControllerName")', type: "POST", processData: false,
            data: data, dataType: 'json',
            contentType: false,
            success: function (data) {
                var response=data.JsonData;               
            },
            error: function (er) { }

        });

服务器端代码

if (System.Web.HttpContext.Current.Request.Files.AllKeys.Any())
                {
                    var pic = System.Web.HttpContext.Current.Request.Files["filekey"];
                    HttpPostedFileBase filebase = new HttpPostedFileWrapper(pic);
                    var fileName = Path.GetFileName(filebase.FileName);


                    string fileExtension = System.IO.Path.GetExtension(fileName);

                    if (fileExtension == ".xls" || fileExtension == ".xlsx")
                    {
                        string FileName = Guid.NewGuid().GetHashCode().ToString("x");
                        string dirLocation = Server.MapPath("~/Content/PacketExcel/");
                        if (!Directory.Exists(dirLocation))
                        {
                            Directory.CreateDirectory(dirLocation);
                        }
                        string fileLocation = Server.MapPath("~/Content/PacketExcel/") + FileName + fileExtension;
                        filebase.SaveAs(fileLocation);
}
}

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" />
}

MemoryStream.GetBuffer() can return extra empty bytes at the end of the byte[], but you can fix that by using MemoryStream.ToArray() instead. However, I found this alternative to work perfectly for all file types:

using (var binaryReader = new BinaryReader(file.InputStream))
{
    byte[] array = binaryReader.ReadBytes(file.ContentLength);
}
Here's my full code:

Document Class:

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;
    }
}
File Download:

[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);
}
File Upload:

[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");
    }
}
View (snippet):

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