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);
}
}

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。

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");        
    }
}

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。

检查我的解决方案

public string SaveFile(HttpPostedFileBase uploadfile, string saveInDirectory="/", List<string> acceptedExtention =null)
{
    acceptedExtention = acceptedExtention ?? new List<String>() {".png", ".Jpeg"};//optional arguments

    var extension = Path.GetExtension(uploadfile.FileName).ToLower();

    if (!acceptedExtention.Contains(extension))
    {
        throw new UserFriendlyException("Unsupported File type");
    }
    var tempPath = GenerateDocumentPath(uploadfile.FileName, saveInDirectory);
    FileHelper.DeleteIfExists(tempPath);
    uploadfile.SaveAs(tempPath);

    var fileName = Path.GetFileName(tempPath);
    return fileName;
}

private string GenerateDocumentPath(string fileName, string saveInDirectory)
{
    System.IO.Directory.CreateDirectory(Server.MapPath($"~/{saveInDirectory}"));
    return Path.Combine(Server.MapPath($"~/{saveInDirectory}"), Path.GetFileNameWithoutExtension(fileName) +"_"+ DateTime.Now.Ticks + Path.GetExtension(fileName));
}

在基本控制器中添加这些函数，以便可以在所有控制器中使用它们

检查如何使用它

SaveFile(view.PassportPicture,acceptedExtention:new List<String>() { ".png", ".Jpeg"},saveInDirectory: "content/img/PassportPicture");

下面是一个完整的例子

[HttpPost]
public async Task<JsonResult> CreateUserThenGenerateToken(CreateUserViewModel view)
{// CreateUserViewModel contain two properties of type HttpPostedFileBase  
    string passportPicture = null, profilePicture = null;
    if (view.PassportPicture != null)
    {
        passportPicture = SaveFile(view.PassportPicture,acceptedExtention:new List<String>() { ".png", ".Jpeg"},saveInDirectory: "content/img/PassportPicture");
    }
    if (view.ProfilePicture != null)
    {
        profilePicture = SaveFile(yourHttpPostedFileBase, acceptedExtention: new List<String>() { ".png", ".Jpeg" }, saveInDirectory: "content/img/ProfilePicture");
    }
    var input = view.MapTo<CreateUserInput>();
    input.PassportPicture = passportPicture;
    input.ProfilePicture = profilePicture;


    var getUserOutput = await _userAppService.CreateUserThenGenerateToken(input);
    return new AbpJsonResult(getUserOutput);
    //return Json(new AjaxResponse() { Result = getUserOutput, Success = true });

}