我在编辑回数据库后尝试保存数据。问题在于文件上传。我每次想要保存编辑数据时都要上传新图像，否则控制器会认为我的img属性为null。所以我将我的编辑操作重写为喜欢这样，希望它能使用我上传的图像
[HttpPost]
[ValidateAntiForgeryToken]
[ValidateInput(false)]
public ActionResult Edit([Bind(Include = "id,name,info,whatThisTeach,whatToKnow")] Major major, HttpPostedFileBase img)
{
if (ModelState.IsValid)
{
if(img != null)
{
major.img = new byte[img.ContentLength];
img.InputStream.Read(major.img, 0, img.ContentLength);
}
else
{
var m = db.Majors.Find(major.id);
major.img = m.img;
}
db.Entry(major).State = EntityState.Modified;
db.SaveChanges();
return RedirectToAction("Index");
}
return View("Details", major);
}
但是当我尝试编辑数据而不上传新图片时，它给了我这个错误：
System.InvalidOperationException HResult = 0x80131509
消息=附加类型＆＃39; MUC.Models.Major＆＃39;的实体。失败是因为 另一个相同类型的实体已经拥有相同的主键 值。使用＆＃39;附加＆＃39;方法或设置 一个实体的状态为“未变”＆＃39;或者＆＃39;修改＆＃39;如果有任何实体 图表具有冲突的键值。这可能是因为某些实体 是新的，尚未收到数据库生成的键值。在 这种情况使用＆＃39;添加＆＃39;方法或“添加”＃39;实体状态跟踪 图表然后将非新实体的状态设置为“未更改”。要么 ＆＃39;变形＆＃39;作为适当的。 Source = EntityFramework StackTrace：
在 System.Data.Entity.Core.Objects.ObjectContext.VerifyRootForAdd（布尔 doAttach，String entitySetName，IEntityWrapper wrappedEntity， EntityEntry existingEntry，EntitySet＆amp; entitySet，Boolean＆amp; isNoOperation）at System.Data.Entity.Core.Objects.ObjectContext.AttachTo（字符串 entitySetName，Object entity）at System.Data.Entity.Internal.Linq.InternalSet1.<>c__DisplayClassa.<Attach>b__9() at System.Data.Entity.Internal.Linq.InternalSet1.ActOnSet（动作 action，EntityState newState，Object entity，String methodName）at System.Data.Entity.Internal.Linq.InternalSet1.Attach(Object entity)1.set_State（EntityState 价值）在MUC.Controllers.MajorsController.Edit（主要专业， HttpPostedFileBase img）中 C：\用户\三池\桌面\ MUC \ MUC \ \控制器MajorsController.cs：行 101.在System.Web.Mvc.ActionMethodDispatcher.Execute（ControllerBase controller，Object []参数）at System.Web.Mvc.ReflectedActionDescriptor.Execute（ControllerContext controllerContext，IDictionary
at System.Data.Entity.Internal.InternalEntityEntry.set_State(EntityState value) at System.Data.Entity.Infrastructure.DbEntityEntry2 parameters) at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary2 参数）at System.Web.Mvc.Async.AsyncControllerActionInvoker.b__39（IAsyncResult的 asyncResult，ActionInvocation innerInvokeState）at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult2.CallEndDelegate(IAsyncResult asyncResult) at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase1.End（） 在 System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod（IAsyncResult的 asyncResult）at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.b__3d（） 在 System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters＆LT;＆GT; c__DisplayClass46.b__3f（）
这是我的编辑视图：
@model MUC.Models.Major
@{
Layout = null;
}
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width" />
<title>Edit</title>
</head>
<body>
<script src="~/Scripts/jquery-1.10.2.min.js"></script>
<script src="~/Scripts/jquery.validate.min.js"></script>
<script src="~/Scripts/jquery.validate.unobtrusive.min.js"></script>
<script src="~/Scripts/ckeditor/ckeditor.js"></script>
@using (Html.BeginForm("Edit", "Majors", FormMethod.Post, new { enctype = "multipart/form-data" }))
{
@Html.AntiForgeryToken()
<div class="form-horizontal">
<h4>Major</h4>
<hr />
@Html.ValidationSummary(true, "", new { @class = "text-danger" })
<div class="form-group">
@Html.LabelFor(model => model.img, htmlAttributes: new { @class = "control-label col-md-2" })
<div class="col-md-10">
@if (Model.img != null)
{
var base64 = Convert.ToBase64String(Model.img);
var imgsrc = string.Format("data:image/jpg;base64,{0}", base64);
<img src="@imgsrc" /><br/>
<input type="file" id="img" name="img"/>
}
else
{
<input type="file" id="img" name="img"/>
}
@Html.ValidationMessageFor(model => model.img, "", new { @class = "text-danger" })
</div>
</div>
<div class="form-group">
@Html.LabelFor(model => model.name, htmlAttributes: new { @class = "control-label col-md-2" })
<div class="col-md-10">
@Html.EditorFor(model => model.name, new { htmlAttributes = new { @class = "form-control" } })
@Html.ValidationMessageFor(model => model.name, "", new { @class = "text-danger" })
</div>
</div>
<div class="form-group">
@Html.LabelFor(model => model.info, htmlAttributes: new { @class = "control-label col-md-2" })
<div class="col-md-10">
@Html.EditorFor(model => model.info, new { htmlAttributes = new { @id = "info", @class = "form-control" } })
@Html.ValidationMessageFor(model => model.info, "", new { @class = "text-danger" })
</div>
</div>
<div class="form-group">
@Html.LabelFor(model => model.whatThisTeach, htmlAttributes: new { @class = "control-label col-md-2" })
<div class="col-md-10">
@Html.TextAreaFor(model => model.whatThisTeach, new { htmlAttributes = new { @class = "form-control", @id = "whatThisTeach" } })
<script type="text/javascript">CKEDITOR.replace('whatThisTeach');</script>
@Html.ValidationMessageFor(model => model.whatThisTeach, "", new { @class = "text-danger" })
</div>
</div>
<div class="form-group">
@Html.LabelFor(model => model.whatToKnow, htmlAttributes: new { @class = "control-label col-md-2" })
<div class="col-md-10">
@Html.TextAreaFor(model => model.whatToKnow, new { htmlAttributes = new { @class = "form-control", @id = "whatToKnow" } })
<script type="text/javascript">CKEDITOR.replace('whatToKnow');</script>
@Html.ValidationMessageFor(model => model.whatToKnow, "", new { @class = "text-danger" })
</div>
</div>
<div class="form-group">
<div class="col-md-offset-2 col-md-10">
<input type="submit" value="Save" class="btn btn-default" />
</div>
</div>
</div>
}
<div>
@Html.ActionLink("Back to List", "Index")
</div>
</body>
</html>