<form id="form1" runat="server" action="/bookIndex/fileUpLoad/(你準備處理的 ActionResult)" method="post" enctype="multipart/form-data">
<input type="file" id="imageUpLoad" name="imageUpLoad">
<input type="button" value="點擊上傳" onclick="UpLoad()">
....
</form>

<script type="text/javascript">
function UpLoad()
{
如果有其他的值，判斷下是否為空.
form1.submit();
}
<script>

public ActionResult fileUpLoad(HttpPostedFileBase imageUpLoad(這里跟前臺頁面input輸入框name保持一致))
{
string fileName = imageUpLoad.FileName;
//轉換只取得文件名，去掉路徑。
if (fileName.LastIndexOf("\\") > -1)
{
fileName = fileName.Substring(fileName.LastIndexOf("\\") + 1);
}
//保存到相對路徑下。
imageUpLoad.SaveAs(Server.MapPath("../../image/img/" + fileName));
//以下代碼是將 路徑保存到數據庫。
string ImagePath = "../../image/img/" + fileName;
string sql = "insert into bookinfo(bookphoto)values('" + ImagePath + "')";
//封裝好的代碼，直接調用。
DataBase db = new DataBase();
db.getConn();
int result = db.executeUpdate(sql);
return View();
}