corrigido:
<div class="ui fluid action input">
<form id="fileupload" action="[URL DE DESTINO, EDITE AQUI]" method="POST" enctype="multipart/form-data">
<input type="hidden" id="conteudoID" name="conteudoID" value="@ViewBag.ID" />
<input type="hidden" id="conteudoNome" name="conteudoNome" value="@ViewBag.Nome" />
<input type="text" id="tbx-file-path" value="Nenhum Arquivo Selecionado..." readonly="readonly" />
@Html.TextBoxFor(m => m.MyFile, new { id = "fu-my-simple-upload", type = "file" , style = "display: none", accept = ".jpg, .png, .pdf, .doc, .docx" })