原因是因为自己的form表单内没有添加
enctype = "multipart/form-data"
@using (Html.BeginForm("UpLoadImg", "FamousStory", FormMethod.Post, new { enctype = "multipart/form-data", name = "upform", id = "upform" }))
{
<table align="center" style="width: 700px; text-align: center; border-style: ridge;
border-width: 3pt">
<th colspan="3">
<font color="red" size="25" align="left">单一图片分类上传</font>
</th>
<tr>
<td align="center">
<input type="file" > }