<div><asp:Image ImageUrl="~/uploads/1.jpg" ID="img2" runat="server" Width="150px" Height="150px" /><asp:FileUpload runat="server" ID="fupImage" /><input type="button" value="上传" id="btnSubmit" runat="server" onserverclick="btnSubmit_ServerClick" />
</div>

protected void btnSubmit_ServerClick(object sender, EventArgs e)
{if (fupImage.HasFile){Regex regex = new Regex(@".(?i:jpg|jpeg|gif|png)$");if (regex.IsMatch(Path.GetExtension(fupImage.FileName))){string path = AppDomain.CurrentDomain.BaseDirectory + "uploads";if (!Directory.Exists(path))Directory.CreateDirectory(path);string filePath = fupImage.FileName;  //此处需要处理同名文件
            fupImage.SaveAs(Path.Combine(path, filePath));img2.ImageUrl = "~/uploads/" + filePath;}}
}

<div><asp:Image ImageUrl="~/uploads/1.jpg" ID="img2" runat="server" Width="150px" Height="150px" /><input type="file" runat="server" id="fileimg" /><input type="button" value="上传" id="btnSubmit" runat="server" onserverclick="btnSubmit_ServerClick" />
</div>

if (fileimg.PostedFile.ContentLength > 0)
{string fileName = Path.GetFileName(fileimg.PostedFile.FileName);Regex regex = new Regex(@".(?i:jpg|jpeg|gif|png)$");if (regex.IsMatch(Path.GetExtension(fileName))){string path = AppDomain.CurrentDomain.BaseDirectory + "uploads";if (!Directory.Exists(path))Directory.CreateDirectory(path);fileimg.PostedFile.SaveAs(Path.Combine(path, fileName));img2.ImageUrl = "~/uploads/" + fileName;}
}

<div><asp:Image ImageUrl="~/uploads/1.jpg" ID="img2" runat="server" Width="150px" Height="150px" /><input type="file" runat="server" id="fileimage"/><input type="button" value="上传" id="btnSubmit" runat="server" onserverclick="btnSubmit_ServerClick" />
</div>

if (Request.Files["fileimage"].HasFile())
{string fileName = Path.GetFileName(Request.Files["fileimage"].FileName);  //此处位需要处理同名文件Regex regex = new Regex(@".(?i:jpg|jpeg|gif|png)$");if (regex.IsMatch(Path.GetExtension(fileName))){string path = AppDomain.CurrentDomain.BaseDirectory + "uploads";if (!Directory.Exists(path))Directory.CreateDirectory(path);Request.Files["fileimage"].SaveAs(Path.Combine(path, fileName));img2.ImageUrl = "~/uploads/" + fileName;}
}

public static void Upload(string filePath){    var request = System.Web.HttpContext.Current.Request;    foreach (string upload in request.Files)    {        HttpPostedFile hp = request.Files[upload];        if (hp.HasFile())        {            CreateFolderIfNeeded(filePath);            string fileName = Path.GetFileName(hp.FileName);  //此处位需要处理同名文件            hp.SaveAs(Path.Combine(filePath, fileName));        }    }}

private static void CreateFolderIfNeeded(string path) {if (!Directory.Exists(path)) {try {Directory.CreateDirectory(path);}catch (Exception) {/*TODO: You must process this exception.*///throw new ArgumentException(Environment.GetResourceString("Argument_PathEmpty"));}}
}

public static class HttpPostFileExtensions {   //扩展方法必须在顶级类中定义public static bool HasFile(this HttpPostedFile file) {return (file != null && file.ContentLength > 0) ? true : false;}
}

@using (Html.BeginForm("Index", "Home", FormMethod.Post, new { id = "form1", enctype = "multipart/form-data" }))
{<img src="/uploads/1.jpg" alt="暂无图片" id="img1" style="width:150px;height:150px;" /><input type='file' name='file' id='file' /><input type="button" value="上传" id="btnSubnit" />
}
<script src="~/Scripts/jquery-1.4.1.min.js"></script>
<script src="~/Scripts/jquery-form.js"></script>
<script type="text/javascript">$(document).ready(function () {$("#file").bind("change", function () {$("#form1").ajaxSubmit({success: function (data) {$("#img1").attr("src", data.filePath);}});});});
</script>

[HttpPost]
public ActionResult Index(HttpPostedFileBase file/*这里的参数暂时无用*/)
{string path = AppDomain.CurrentDomain.BaseDirectory + "uploads";UpLoadFileHelper.Upload(path);var filePath = "/uploads/" + Path.GetFileName(Request.Files["file"].FileName);return Json(new { filePath = filePath });
}

[HttpPost]
public ActionResult Index(HttpPostedFileBase file)
{if (null != file && file.ContentLength>0){string path = AppDomain.CurrentDomain.BaseDirectory + "uploads";if (!Directory.Exists(path)){Directory.CreateDirectory(path);}string fileName = string.Empty;fileName = Path.GetFileName(file.FileName);file.SaveAs(Path.Combine(path, fileName));return Json(new { filePath = "/uploads/" + fileName, code = 1 });}return Json(new { filePath = "请选择需要上传的文件", code = 0 });
}

<div class="file-wrapper"><input type="file" /><span class="button">Choose a file</span>
</div>

<script src="jquery.js"></script>
<script type="text/javascript">var SITE = SITE || {};SITE.fileInputs = function () {var $this = $(this),$val = $this.val(),valArray = $val.split('\\'),newVal = valArray[valArray.length - 1],$button = $this.siblings('.button'),$fakeFile = $this.siblings('.file-holder');if (newVal !== '') {$button.text('File Chosen');if ($fakeFile.length === 0) {$button.after('<span class="file-holder">' + newVal + '</span>');} else {$fakeFile.text(newVal);}}};$(document).ready(function () {$('.file-wrapper input[type=file]').bind('change focus click', SITE.fileInputs);});
</script>

<style type="text/css">.file-wrapper {position: relative;display: inline-block;overflow: hidden;cursor: pointer;}.file-wrapper input {position: absolute;top: 0;right: 0;filter: alpha(opacity=1);opacity: 0.01;-moz-opacity: 0.01;cursor: pointer;}.file-wrapper .button {color: #fff;background: #117300;padding: 4px 18px;margin-right: 5px;border-radius: 5px;-moz-border-radius: 5px;-webkit-border-radius: 5px;display: inline-block;font-weight: bold;cursor: pointer;}.file-holder {color: #000;}
</style>