Opening a byte stream file using asp.net mvc

<li class="thumpimage">
                        <%=Html.Hidden("attachmtId", item.ILDAttachmentId) %>
                        <img src="<%=imgurl %>" alt="test" height="81" width="76" />
                        <span class="thumb_descrp">
                            <%=item.ILDAttachmentName %></span></li>

The jquery part is as follows

$(document).ready(function() {

        $(".thumpimage").click(function() {
            var attchmtId = $("#attachmtId").val();
            alert(attchmtId);
            $.post('/Instruction/OpenInstnDoc', { attchId: attchmtId });
        });
    });

And the function开发者_高级运维 in the controller is

 public ActionResult OpenInstnDoc(int attchId)
    {

        Attachment objAttach = new Attachment();
        objAttach = objAttach.GetAttachmentById(attchId);

        byte[] theData = objAttach.BinaryFile;
        Response.AddHeader("content-length", theData.Length.ToString());
        Response.AddHeader("content-disposition", "inline; filename=" + objAttach.AttachmentName + "");
        return File(theData, objAttach.MineType);
    }

I am not able open the file. Can anyone help me on this?

You cannot use ajax to stream file content to the browser and expect to be prompted with a file open/save dialog. Instead of the call to $.post, try

$(document).ready(function() {

    $(".thumpimage").click(function() {
        var attchmtId = $("#attachmtId").val();
        alert(attchmtId);
        //$.post('/Instruction/OpenInstnDoc', { attchId: attchmtId });
        window.location.href = "/Instruction/OpenInstnDoc/" + attchmtId;
    });
});