blocks|key|3254465|text|据我所知，您不能设置HTML文件输入框的值。我建议将文件输入框与标签或文本框结合起来。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3254466|然后，您可以使用文件输入框中的值填充它，以便稍后重新提交。|3254467|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

<p>As far as I know you cannot set the value of a HTML file input box. 
I would suggest coupling the file input box with a label or text box.</p>

<p>Then you can populate the it with the value from the file input box to be resubmitted later.</p>


blocks|key|413974|text|由于存在安全风险，浏览器就是这样设计的。不可能在HTML源代码或Javascript中设置文件输入框的值。否则，恶意脚本可能会在用户不注意的情况下窃取一些私有文件。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|413975|有关于这个主题的an+interesting+information。|offset|length|413976|entityMap|0|LINK|mutability|MUTABLE|url|http://www.cs.tut.fi/~jkorpela/forms/file.html#value^0|0|8|Q|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

<p>Browsers are designed in such way because of security risks. It's impossible to set value of file input box in HTML source or by Javascript. Otherwise malicious script could steal some private file without user attention.</p>

<p>There is <a href="http://www.cs.tut.fi/~jkorpela/forms/file.html#value" rel="noreferrer">an interesting information</a> about the subject.</p>


blocks|key|410614|text|有基于闪存的文件上传器。试试他们中的一个。如果不支持flash和java脚本，他们中的一些人甚至会回到常规的文件输入框。我建议寻找jQuery插件。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|410615|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

<p>There are flash based file uploaders. Try one of them. Some of them even falls back to regular file input box if flash and java script is not supported. I advise to look for jQuery plugins. </p>


blocks|key|410621|text|如果文件不是太大，你可以base64它并使用它作为一个隐藏字段的值。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|410622|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

<p>If the file isn't too big you could base64 it and use this as value for a hidden field.</p>


blocks|key|3467689|text|不能设置HTML文件输入框的值。一种解决方法是，在验证后输出表单时，将文件上载框替换为隐藏的输入字段。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3467690|提交时，使用文件输入框(稍后重新提交)中的值填充隐藏字段。请记住，在任何时候都要显示文件上载或隐藏字段名(而不是两者)：|3467691|注意：以下代码仅用于说明/解释目的。将其替换为适用于您使用的语言的代码。|offset|length|style|BOLD|3467692|<?php+/*+You+may+need+to+sanitize+the+value+of+$_POST['file_upload'];+
*+this+is+just+a+start+*/
if(isset($_POST['file_upload'])+&&+!empty($_POST['file_upload'])){+?>
<input+type="hidden"+name="file_upload"+value="<?php+print($_POST['file_upload']);+?>"+/>
<?php+}+else+{+?>
<input+type="file"+name="file_upload"+/>
<?php+}+?>|code-block|syntax|javascript|3467693|entityMap^0|0|0|0|3|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|S|8|@$F|T|G|U|H|I]]|9|@]|A|$]]|$1|J|3|K|5|L|7|V|8|@]|9|@]|A|$M|N]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

<p>You cannot set the value of a HTML file input box. As a workaround, replace the file upload box with a hidden input field when outputting the form after validation.</p>

<p>On submission, you populate the hidden field with the value from the file input box (to be resubmitted later). Remember to have either the file upload or hidden field name present at any one time (not both):</p>

<p><strong>Note:</strong> The code below is for <em>illustration/explanation</em> purposes only. Replace it with the code appropriate to the language you use.</p>

<pre><code>&lt;?php /* You may need to sanitize the value of $_POST['file_upload']; 
* this is just a start */
if(isset($_POST['file_upload']) &amp;&amp; !empty($_POST['file_upload'])){ ?&gt;
&lt;input type="hidden" name="file_upload" value="&lt;?php print($_POST['file_upload']); ?&gt;" /&gt;
&lt;?php } else { ?&gt;
&lt;input type="file" name="file_upload" /&gt;
&lt;?php } ?&gt;
</code></pre>


blocks|key|3467739|text|我建议您提前通过ajax进行验证，并进行部分页面更新。在这种情况下，您不会丢失该文件。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3467740|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

<p>I would recommend doing the validation beforehand via ajax and do a partial page update. In this case, you will not lose the file.</p>


blocks|key|413685|text|我不同意将“不可能”标记为正确答案。如果有人还在寻找一种可能性，这里是为我工作的周围工作。我使用的是MVC5。其思想是使用会话变量。我是从ASP.Net+Form得到这个想法的。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|413686|My+Model/ViewModel+(仅限相关属性)：|413687|public+partial+class+emp_leaves
++++{
++++++++public+string+fileNameOrig+{+get;+set;+}
++++++++public+byte[]+fileContent+{+get;+set;+}

++++++++public+HttpPostedFileBase+uploadFile+{+get;+set;+}
++++}|code-block|syntax|javascript|413688|在我的控制器(HttpPost)中://检查|413689|[HttpPost]
[ValidateAntiForgeryToken]
public+ActionResult+Edit(emp_leaves+emp_leaves)
{
++++if+(emp_leaves.uploadFile+!=+null+&&+emp_leaves.uploadFile.ContentLength>0+&&+!string.IsNullOrEmpty(emp_leaves.uploadFile.FileName))
++++{
++++++++emp_leaves.fileNameOrig+=+Path.GetFileName(emp_leaves.uploadFile.FileName);
++++++++emp_leaves.fileContent+=+new+byte[emp_leaves.uploadFile.ContentLength];
++++++++emp_leaves.uploadFile.InputStream.Read(emp_leaves.fileContent,+0,+emp_leaves.uploadFile.ContentLength);
++++++++Session["emp_leaves.uploadFile"]+=+emp_leaves.uploadFile;+//saving+the+file+in+session+variable+here
++++}
++++else+if+(Session["emp_leaves.uploadFile"]+!=+null)
++++{//if+re-submitting+after+a+failed+validation+you+will+reach+here.
++++++++emp_leaves.uploadFile+=+(HttpPostedFileBase)Session["emp_leaves.uploadFile"];
++++++++if+(emp_leaves.uploadFile+!=+null+&&+emp_leaves.uploadFile.ContentLength>0+&&+!string.IsNullOrEmpty(emp_leaves.uploadFile.FileName))
++++++++{
++++++++++++emp_leaves.fileNameOrig+=+Path.GetFileName(emp_leaves.uploadFile.FileName);
++++++++++++emp_leaves.uploadFile.InputStream.Position+=+0;
++++++++++++emp_leaves.fileContent+=+new+byte[emp_leaves.uploadFile.ContentLength];
++++++++++++emp_leaves.uploadFile.InputStream.Read(emp_leaves.fileContent,+0,+emp_leaves.uploadFile.ContentLength);++++
++++++++}
++++}
//code+to+save+follows+here...
}|413690|最后，在我的编辑视图中:在这里，我有条件地显示了文件上传控件。|413691|​|413692|<+script+type+=+"text/javascript"+>
++$("#removefile").on("click",+function(e)+{
++++if+(!confirm('Delete+File?'))+{
++++++e.preventDefault();
++++++return+false;
++++}
++++$('#fileNameOrig').val('');
++++//toggle+visibility+for+concerned+div
++++$('#downloadlrfdiv').hide();
++++$('#uploadlrfdiv').show();
++++return+false;
++});+<
/script>|413693|<script+src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script>
@model+PPMSWEB.Models.emp_leaves+@{+HttpPostedFileBase+uploadFileSession+=+Session["emp_leaves.uploadFile"]+==+null+?+null+:+(HttpPostedFileBase)Session["emp_leaves.uploadFile"];+}+@using+(Html.BeginForm(null,+null,+FormMethod.Post,+new+{+enctype+=+"multipart/form-data"
}))+{+@Html.AntiForgeryToken()
<div+class="row">
++@*irrelevant+content+removed*@
++<div+id="downloadlrfdiv"+@((!String.IsNullOrEmpty(Model.fileNameOrig)+&&+(Model.uploadFile==n+ull+%7C%7C+uploadFileSession+!=null))+?+""+:+"style=display:none;")>
++++<label>Attachment</label>
++++<span>
++++++++++++<strong>
++++++++++++++++<a+id="downloadlrf"+href="@(uploadFileSession+!=+null?+""+:+Url.Action("DownloadLRF",+"emp_leaves",+new+{+empLeaveId+=+Model.ID+}))"+class="text-primary+ui-button-text-icon-primary"+title="Download+attached+file">
++++++++++++++++++++@Model.fileNameOrig
++++++++++++++++</a>
++++++++++++</strong>
++++++++++++@if+(isEditable+&&+!Model.readonlyMode)
++++++++++++{
++++++++++++++++@Html.Raw("&nbsp");
++++++++++++++++<a+id="removefile"+class="btn+text-danger+lead">
++++++++++++++++++++<strong+title="Delete+File"+class="glyphicon+glyphicon-minus-sign">++</strong>
++++++++++++++++</a>
++++++++++++}
++++++++++++</span>
++</div>
++<div+id="uploadlrfdiv"+@(!(!String.IsNullOrEmpty(Model.fileNameOrig)+&&+Model.uploadFile==n+ull)+&&+!Model.readonlyMode+?+""+:+"style=display:none;")>
++++<label>Upload+File</label>+@Html.TextBoxFor(model+=>+model.uploadFile,+new+{+@type+=+"file",+@class+=+"btn+btn-default",+@title+=+"Upload+file+(max+300+KB)"+})+@Html.ValidationMessageFor(x+=>+x.uploadFile)
++</div>
</div>
}|413694|413695|entityMap|0|LINK|mutability|MUTABLE|url|https://forums.asp.net/t/1895657.aspx?ASP%2520NET%2520MVC%25204%2520Browser%2520looses%2520uploading%2520File%2520after%2520Postback^0|1X|C|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|15|8|@]|9|@$A|16|B|17|1|18]]|C|$]]|$1|D|3|E|5|6|7|19|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|1A|8|@]|9|@]|C|$I|J]]|$1|K|3|L|5|6|7|1B|8|@]|9|@]|C|$]]|$1|M|3|N|5|H|7|1C|8|@]|9|@]|C|$I|J]]|$1|O|3|P|5|6|7|1D|8|@]|9|@]|C|$]]|$1|Q|3|R|5|6|7|1E|8|@]|9|@]|C|$]]|$1|S|3|T|5|H|7|1F|8|@]|9|@]|C|$I|J]]|$1|U|3|V|5|H|7|1G|8|@]|9|@]|C|$I|J]]|$1|W|3|R|5|6|7|1H|8|@]|9|@]|C|$]]|$1|X|3|-4|5|6|7|1I|8|@]|9|@]|C|$]]]|Y|$Z|$5|10|11|12|C|$13|14]]]]

<p>I fail to agree with "impossible" being marked as correct answer.
In case anybody is still in search of a possibility, here is the work around that worked for me. I'm using MVC5. The idea is to use a session variable. I got the idea from <a href="https://forums.asp.net/t/1895657.aspx?ASP%20NET%20MVC%204%20Browser%20looses%20uploading%20File%20after%20Postback" rel="nofollow noreferrer" title="asp.net forum">ASP.Net Form</a>.</p>

<p>My Model/ViewModel (only relevant properties):</p>

<pre><code>public partial class emp_leaves
    {
        public string fileNameOrig { get; set; }
        public byte[] fileContent { get; set; }

        public HttpPostedFileBase uploadFile { get; set; }
    }
</code></pre>

<p>In my controller (HttpPost):
//Check</p>

<pre><code>[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Edit(emp_leaves emp_leaves)
{
    if (emp_leaves.uploadFile != null &amp;&amp; emp_leaves.uploadFile.ContentLength&gt;0 &amp;&amp; !string.IsNullOrEmpty(emp_leaves.uploadFile.FileName))
    {
        emp_leaves.fileNameOrig = Path.GetFileName(emp_leaves.uploadFile.FileName);
        emp_leaves.fileContent = new byte[emp_leaves.uploadFile.ContentLength];
        emp_leaves.uploadFile.InputStream.Read(emp_leaves.fileContent, 0, emp_leaves.uploadFile.ContentLength);
        Session["emp_leaves.uploadFile"] = emp_leaves.uploadFile; //saving the file in session variable here
    }
    else if (Session["emp_leaves.uploadFile"] != null)
    {//if re-submitting after a failed validation you will reach here.
        emp_leaves.uploadFile = (HttpPostedFileBase)Session["emp_leaves.uploadFile"];
        if (emp_leaves.uploadFile != null &amp;&amp; emp_leaves.uploadFile.ContentLength&gt;0 &amp;&amp; !string.IsNullOrEmpty(emp_leaves.uploadFile.FileName))
        {
            emp_leaves.fileNameOrig = Path.GetFileName(emp_leaves.uploadFile.FileName);
            emp_leaves.uploadFile.InputStream.Position = 0;
            emp_leaves.fileContent = new byte[emp_leaves.uploadFile.ContentLength];
            emp_leaves.uploadFile.InputStream.Read(emp_leaves.fileContent, 0, emp_leaves.uploadFile.ContentLength);    
        }
    }
//code to save follows here...
}
</code></pre>

<p>Finally within my edit view: here, i am conditionally showing the file upload control.</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>&lt; script type = "text/javascript" &gt;
  $("#removefile").on("click", function(e) {
    if (!confirm('Delete File?')) {
      e.preventDefault();
      return false;
    }
    $('#fileNameOrig').val('');
    //toggle visibility for concerned div
    $('#downloadlrfdiv').hide();
    $('#uploadlrfdiv').show();
    return false;
  }); &lt;
/script&gt;</code></pre>
<pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"&gt;&lt;/script&gt;
@model PPMSWEB.Models.emp_leaves @{ HttpPostedFileBase uploadFileSession = Session["emp_leaves.uploadFile"] == null ? null : (HttpPostedFileBase)Session["emp_leaves.uploadFile"]; } @using (Html.BeginForm(null, null, FormMethod.Post, new { enctype = "multipart/form-data"
})) { @Html.AntiForgeryToken()
&lt;div class="row"&gt;
  @*irrelevant content removed*@
  &lt;div id="downloadlrfdiv" @((!String.IsNullOrEmpty(Model.fileNameOrig) &amp;&amp; (Model.uploadFile==n ull || uploadFileSession !=null)) ? "" : "style=display:none;")&gt;
    &lt;label&gt;Attachment&lt;/label&gt;
    &lt;span&gt;
            &lt;strong&gt;
                &lt;a id="downloadlrf" href="@(uploadFileSession != null? "" : Url.Action("DownloadLRF", "emp_leaves", new { empLeaveId = Model.ID }))" class="text-primary ui-button-text-icon-primary" title="Download attached file"&gt;
                    @Model.fileNameOrig
                &lt;/a&gt;
            &lt;/strong&gt;
            @if (isEditable &amp;&amp; !Model.readonlyMode)
            {
                @Html.Raw("&amp;nbsp");
                &lt;a id="removefile" class="btn text-danger lead"&gt;
                    &lt;strong title="Delete File" class="glyphicon glyphicon-minus-sign"&gt;  &lt;/strong&gt;
                &lt;/a&gt;
            }
            &lt;/span&gt;
  &lt;/div&gt;
  &lt;div id="uploadlrfdiv" @(!(!String.IsNullOrEmpty(Model.fileNameOrig) &amp;&amp; Model.uploadFile==n ull) &amp;&amp; !Model.readonlyMode ? "" : "style=display:none;")&gt;
    &lt;label&gt;Upload File&lt;/label&gt; @Html.TextBoxFor(model =&gt; model.uploadFile, new { @type = "file", @class = "btn btn-default", @title = "Upload file (max 300 KB)" }) @Html.ValidationMessageFor(x =&gt; x.uploadFile)
  &lt;/div&gt;
&lt;/div&gt;
}</code></pre>
</div>
</div>
</p>


<p>I've got a simple form in an MVC app I've made. It contains a file field so users can upload an image. It all works great.</p>

<p>Problem is, if the form submit fails validation the content of the file field is lost (other fields remain populated, thx HtmlHelpers!). <strong>How do I keep the file field populated after a failed validation?</strong></p>

<p>TIA!</p>


How to keep input type=file field value after failed validation in ASP.NET MVC?

jQuery

在我制作的MVC应用程序中，我有一个简单的表单。它包含一个文件字段，以便用户可以上传图像。这一切都很好用。问题是，如果表单提交未能通过验证，文件字段的内容就会丢失(其他字段仍然填充，谢谢HtmlHelpers!)。如何在验证失败后保持填充文件字段？蒂娅！

问如何在ASP.NET MVC中验证失败后保留输入的type=file字段值？
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