[英]how to construct url for image saved in database
我遇到了问题。 我的数据库配置正确,图像正确保存在数据库中,但不知道如何为保存在数据库中的图像构建 url,因为我必须将其提供给淘汰赛视图模型进行绑定。
public JsonResult GetPosts()
{
var ret = (from post in db.Posts.ToList()
orderby post.PostedDate descending
select new
{
Message = post.Message,
PostedBy = post.PostedBy,
PostedByName = post.ApplicationUser.UserName,
// having problem at this line dont know how to construct url at this line as i have to supply url
// (String type to the PostedByAvatar)
PostedByAvatar = db.Files.SingleOrDefault(s => s.ApplicationUserId == post.PostedBy),
PostedDate = post.PostedDate,
PostId = post.PostId,
}).AsEnumerable();
return Json(ret, JsonRequestBehavior.AllowGet);
}
这是淘汰赛功能--------
function Post(data) {
var self = this;
data = data || {};
self.PostId = data.PostId;
self.Message = ko.observable(data.Message || "");
self.PostedBy = data.PostedBy || "";
self.PostedByName = data.PostedByName || "";
self.PostedDate = getTimeAgo(data.PostedDate);
self.PostedByAvatar = data.PostedByAvatar || "";
self.error = ko.observable();
self.PostComments = ko.observableArray();
这是从数据库中获取带有图像的现有帖子、评论等的视图模型-----
function viewModel() {
var self = this;
self.posts = ko.observableArray();
self.newMessage = ko.observable();
self.error = ko.observable();
self.loadPosts = function () {
// to load existing posts
$.ajax({
url: postApiUrl1,
datatype: "json",
contentType: "application/json",
cache: false,
type: 'Get'
})
在我的视图页面上,这是用于加载图像的容器框 -----
<ul id="msgHolder" data-bind="foreach: posts">
<li class="postHolder">
<img data-bind="attr: { src: PostedByAvatar }">
<p><a data-bind="text: PostedByName"></a>: <span data-bind=" html: Message"></span></p>
现在,将图像保存在数据库中的模型类是这样的。它有 ApplicationUserId 作为指向 ApplicationUserClass 的外键---
public class File
{
[Key]
public int FileId { get; set; }
[StringLength(255)]
public string FileName { get; set; }
[StringLength(100)]
public string ContentType { get; set; }
public byte[] Content { get; set; }
public FileType FileType { get; set; }
public int ApplicationUserId { get; set; }
public virtual ApplicationUser ApplicationUser { get; set; }
}
和 ApplicationUserClass 是这样的---
public class ApplicationUser : IdentityUser<int, CustomUserLogin, CustomUserRole, CustomUserClaim>
{
public ApplicationUser()
{
this.Posts = new HashSet<Post>();
this.Files = new HashSet<File>();
}
public virtual ICollection<File> Files { get; set; }
public virtual ICollection<Post> Posts { get; set; }
这是保存在数据库中的图像。现在,我想知道如何为保存在数据库中的图像构造 url,因为我必须以字符串形式将其提供给视图模型。 或者有比这更好的方法。
这是我的 Post 类,它与 ApplicationUser 类有多对一的关系,外键是 PostedBy 指向 ApplicationUser 类----
public class Post
{
public Post()
{
this.PostComments = new HashSet<PostComment>();
}
[Key]
public int PostId { get; set; }
public string Message { get; set; }
public int? PostedBy { get; set; }
public System.DateTime PostedDate { get; set; }
public virtual ICollection<PostComment> PostComments { get; set; }
public virtual ApplicationUser ApplicationUser { get; set; }
}
尽管可以将 Base64 字符串作为<img>
的src
传递,但我认为最明智的方法是不从 Ajax 调用中返回实际字节,而是创建一个 url 来请求来自服务器的图像字节.
首先,添加将提供图像数据所需的操作:
[HttpGet]
public FileResult GetFileData(int fileId)
{
var file = db.Files.Single(x => x.FileId == fileId);
return File(file.Content, file.ContentType);
}
现在,更改您的GetPosts
操作以在PostedByAvatar
属性中返回 url:
public JsonResult GetPosts()
{
var ret = (from post in db.Posts.ToList()
orderby post.PostedDate descending)
select new
{
Message = post.Message,
PostedBy = post.PostedBy,
PostedByName = post.ApplicationUser.UserName,
PostedByAvatar = _GenerateAvatarUrlForUser(post.PostedBy),
PostedDate = post.PostedDate,
PostId = post.PostId,
});
return Json(ret, JsonRequestBehavior.AllowGet);
}
private string _GenerateAvatarUrlForUser(int? userId)
{
if (!user.HasValue)
return null;
var avatarImage = db.Files.SingleOrDefault(s => s.ApplicationUserId == userId);
if (avatarImage != null)
return Url.Action("GetFileData", new { fileId = avatarImage.FileId });
return null;
}
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