请注意此代码仅用于上传图像。我使用HTMLHelper上传图像。在cshtml文件中放入以下代码

@using (Html.BeginForm("UploadImageAction", "Admin", FormMethod.Post, new { enctype = "multipart/form-data", id = "myUploadForm" }))
{
    <div class="controls">
       @Html.UploadFile("UploadImage")
    </div>
     <button class="button">Upload Image</button>
}

然后为Upload标记创建HTMLHelper

public static class UploadHelper
{
public static MvcHtmlString UploadFile(this HtmlHelper helper, string name, object htmlAttributes = null)
{
    TagBuilder input = new TagBuilder("input");
    input.Attributes.Add("type", "file");
    input.Attributes.Add("id", helper.ViewData.TemplateInfo.GetFullHtmlFieldId(name));
    input.Attributes.Add("name", helper.ViewData.TemplateInfo.GetFullHtmlFieldName(name));

    if (htmlAttributes != null)
    {
        var attributes = HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes);
        input.MergeAttributes(attributes);
    }

    return new MvcHtmlString(input.ToString());
   }
}

最后在行动中上传你的文件

        [AjaxOnly]
        [HttpPost]
        public ActionResult UploadImageAction(HttpPostedFileBase UploadImage)
        {
           string path = Server.MapPath("~") + "Files\\UploadImages\\" + UploadImage.FileName;
           System.Drawing.Image img = new Bitmap(UploadImage.InputStream);    
           img.Save(path);

           return View();
        }

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">
                             

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 });

}

请注意此代码仅用于上传图像。我使用HTMLHelper上传图像。在cshtml文件中放入以下代码

@using (Html.BeginForm("UploadImageAction", "Admin", FormMethod.Post, new { enctype = "multipart/form-data", id = "myUploadForm" }))
{
    <div class="controls">
       @Html.UploadFile("UploadImage")
    </div>
     <button class="button">Upload Image</button>
}

然后为Upload标记创建HTMLHelper

public static class UploadHelper
{
public static MvcHtmlString UploadFile(this HtmlHelper helper, string name, object htmlAttributes = null)
{
    TagBuilder input = new TagBuilder("input");
    input.Attributes.Add("type", "file");
    input.Attributes.Add("id", helper.ViewData.TemplateInfo.GetFullHtmlFieldId(name));
    input.Attributes.Add("name", helper.ViewData.TemplateInfo.GetFullHtmlFieldName(name));

    if (htmlAttributes != null)
    {
        var attributes = HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes);
        input.MergeAttributes(attributes);
    }

    return new MvcHtmlString(input.ToString());
   }
}

最后在行动中上传你的文件

        [AjaxOnly]
        [HttpPost]
        public ActionResult UploadImageAction(HttpPostedFileBase UploadImage)
        {
           string path = Server.MapPath("~") + "Files\\UploadImages\\" + UploadImage.FileName;
           System.Drawing.Image img = new Bitmap(UploadImage.InputStream);    
           img.Save(path);

           return View();
        }

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" />
}

如果有人想用Ajax上传多个文件，下面是我的文章在Asp.NetMVC中使用Ajax进行多文件上传