每次我更改asp.net mvc时，HttpPostedFileBase为null

如何解决每次我更改asp.net mvc时，HttpPostedFileBase为null

这是我的相册模型课。

public class Album
    {
        [required(ErrorMessage ="Please enter an album title.")]
        public string Title { get; set; }
        [Key]
        public int Id { get; set; }
        [required(ErrorMessage ="Please enter an album price.")]
        [Range(0.01,double.MaxValue,ErrorMessage ="Price cannot be 0 or lower.")]
        public decimal Price { get; set; }
        [required]
        public int ArtistId { get; set; }
        [required]
        public virtual Artist Artist { get; set; }
        [required]
        public int GenreId { get; set; }
        [required]
        public virtual Genre Genre { get; set; }
        
        public byte[] ImageData { get; set; }
        public string ImageMimeType { get; set; }
    }

SaveAlbum方法的存储库和实现

public interface IAlbumRepository
    {
        IEnumerable<Album> Albums { get; }
        void SaveAlbum(Album album);
        Album Deletealbum(int albumId);
    }


public void SaveAlbum(Album album)
        {
            if (album.Id == 0)
            {
                if (context.Albums.Where(a => a.Artist.Name == album.Artist.Name).FirstOrDefault() != null)
                {
                    album.ArtistId = context.Albums.Where(a => a.Artist.Name == album.Artist.Name).FirstOrDefault().ArtistId;
                    album.Artist = context.Albums.Where(a => a.Artist.Name == album.Artist.Name).FirstOrDefault().Artist;
                }
                if (context.Albums.Where(a => a.Genre.Name == album.Genre.Name).FirstOrDefault() != null)
                {
                    album.GenreId = context.Albums.Where(a => a.Genre.Name == album.Genre.Name).FirstOrDefault().GenreId;
                    album.Genre = context.Albums.Where(a => a.Genre.Name == album.Genre.Name).FirstOrDefault().Genre;
                }
                context.Albums.Add(album);
            }
            else
            {
                Album dbEntry = context.Albums.Find(album.Id);
                if (dbEntry!= null)
                {
                    if (context.Albums.Where(a => a.Artist.Name == album.Artist.Name).FirstOrDefault() != null)
                    {
                        dbEntry.ArtistId = context.Albums.Where(a => a.Artist.Name == album.Artist.Name).FirstOrDefault().ArtistId;
                        dbEntry.Artist = context.Albums.Where(a => a.Artist.Name == album.Artist.Name).FirstOrDefault().Artist;
                    }
                    else
                    {
                        dbEntry.ArtistId = album.ArtistId;
                        dbEntry.Artist = album.Artist;
                    }
                    if (context.Albums.Where(a => a.Genre.Name == album.Genre.Name).FirstOrDefault() != null)
                    {
                        dbEntry.GenreId = context.Albums.Where(a => a.Genre.Name == album.Genre.Name).FirstOrDefault().GenreId;
                        dbEntry.Genre = context.Albums.Where(a => a.Genre.Name == album.Genre.Name).FirstOrDefault().Genre;
                    }
                    else
                    {
                        dbEntry.GenreId = album.GenreId;
                        dbEntry.Genre = album.Genre;
                    }
                    dbEntry.Id = album.Id;
                    dbEntry.ImageData = album.ImageData;
                    dbEntry.ImageMimeType = album.ImageMimeType;
                    dbEntry.OrderDetails = album.OrderDetails;
                    dbEntry.Price = album.Price;
                    dbEntry.Title = album.Title;
                }
            }
            context.SaveChanges();
        }

控制器

...
private IAlbumRepository repository;
        public AdminController(IAlbumRepository repo)
        {
            repository = repo;
        }
        public ViewResult Index()
        {
            return View(repository.Albums);
        }
        public ViewResult Edit(int albumId)
        {
            Album album = repository.Albums.FirstOrDefault(m => m.Id == albumId);
            return View(album);
        }
        [HttpPost]
        public ActionResult Edit(Album album,HttpPostedFileBase image = null)
        {
            if (ModelState.IsValid)
            {
                if (image != null)
                {
                    album.ImageMimeType = image.ContentType;
                    album.ImageData = new byte[image.ContentLength];
                    image.InputStream.Read(album.ImageData,image.ContentLength);
                }

                repository.SaveAlbum(album);
                TempData["message"] = string.Format("{0} has been saved",album.Title);
                return RedirectToAction("Index");
            }
            else
            {
                return View(album);
            }
        }}

编辑视图

@model MusicStore1.Models.Album

@{
    ViewBag.Title = "Admit: Edit " + @Model.Title;
    Layout = "~/Views/Shared/_AdminLayout.cshtml";
}
<div>
    <div> <br /></div>
    <div>
        <h3> Edit @Model.Title </h3>
    </div>
    @using (Html.BeginForm("Edit","Admin",FormMethod.Post,new { enctype = "multipart/form-data" }))
    {
        @Html.ValidationSummary()
        <div>
            @Html.HiddenFor(m => m.Id)
            <label> Title </label>
            @Html.TextBoxFor(m => m.Title,null,new { @class = "form-control" })
            <label> Artist </label>
            @Html.TextBoxFor(m => m.Artist.Name,new { @class = "form-control" })
            <label> Genre </label>
             @Html.TextBoxFor(m => m.Genre.Name,new { @class = "form-control" })
            <label> Price  </label>
            @Html.TextBoxFor(m => m.Price,new { @class = "form-control" })
            <div class="form-group">
                <div style="position:relative;">
                    <label> Image </label>
                    <a class="btn" href="javascript:;">
                        <input type="file" name="Image" size="40"
                               style="position:absolute" ;z-index:2;top:0;left:0;filter:alpha(opacity=0);opacity:0;
                               background-color:transparent; color:transparent;"
                               onchange='$("#upload-file-info").html($(this).val());' />
                    </a>
                    <span class="label label-info" id="upload-file-info"></span>
                </div>
                @if (Model.ImageData == null)
                {
                    <div class="form-control-static"> No Image</div>
                }
                else
                {
                    <img class="img-thumbnail" width="150" height="150" src="@Url.Action("Getimage","Album",new { Model.Id })" />
                }
            </div>
        </div>
        <div>
            <input type="submit" value="save" class="btn btn-success" />
            @Html.ActionLink("Cancel and return to List","Index",new
       {
           @class = "btn btn-info"
       })
        </div>
    }
</div>

Getimage方法

 public FileContentResult Getimage(int albumId)
        {
            Album alb = repository.Albums.FirstOrDefault(p => p.Id == albumId);
            if (alb != null)
            {
                return File(alb.ImageData,alb.ImageMimeType);
            }
            else
            {
                return null;
            }
        }

每次我尝试更改相册的某些内容时，例如其标题或价格，在保存更改后我已经保存的图像都会丢失。如果有人能帮助我找出问题所在，我将不胜感激。预先感谢！

解决方法

我认为这一行中有error。您没有从视图中正确传递albumId参数。

<img class="img-thumbnail" width="150" height="150"
    src="@Url.Action("GetImage","Album",new { Model.Id })" />

解决方案： 使用此方法将albumId从view传递到controller

<img class="img-thumbnail" width="150" height="150"
    src="@Url.Action("GetImage",new { albumId = Model.Id })" />