C#上传下载文件

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方法一、通过Ajax方式上传文件（input file）,使用FormData进行Ajax请求

<div >

<input type="file" name="FileUpload" id="FileUpload">

<a class="layui-btn layui-btn-mini" id="btn_uploadimg">上传图片</a>

</div>

<script type="text/jscript">

$(function () {

$("#btn_uploadimg").click(function () {

var fileObj = document.getElementById("FileUpload").files[0]; // js 获取文件对象，（据说IE8 不支持.files写法，未测试）

if (typeof (fileObj) == "undefined" || fileObj.size <= 0) {

alert("请选择图片");

return;

}

var formFile = new FormData();

formFile.append("action", "UploadVMKImagePath");

formFile.append("file", fileObj); //加入文件对象

//第一种 XMLHttpRequest 对象

//var xhr = new XMLHttpRequest();

//xhr.open("post", "/Admin/Ajax/VMKHandler.ashx", true);

//xhr.onload = function () {

// alert("上传完成!");

//};

//xhr.send(formFile);

//第二种 ajax 提交

var data = formFile;

$.ajax({

url: "/Admin/Ajax/VMKHandler.ashx",

data: data,

type: "Post",

dataType: "json",

cache: false,//上传文件无需缓存

processData: false,//用于对data参数进行序列化处理这里必须false

contentType: false, //必须

success: function (result) {

alert("上传完成!");

},

})

</script>

方法二、通过form和input file上传

//必须要有name属性，name属性是用于在前台和后台间建立联系的，form中只有具有name属性的控件，其值才会被传递到后台，而没有name属性的控件后台程序是接收不到它的值的

</form>

<script type="text/jscript">

$(function () {

$("#btn_uploadimg").click(function () {

var options = { type: 'post', data: { Default: "FileUpload",}, url: 'Index.aspx', success: function (data) {

//兼容IE和FireFox var file = $("#UploadFile"); file.after(file.clone().val("")); file.remove();

} }; $('#fmFileUpload_Knowledge').ajaxSubmit(options);

})

</script>

后台

private string FileUpload() { string fileName = string.Empty; string serverPath = string.Empty; try { HttpFileCollection httpFileCollection = Request.Files; if (httpFileCollection.Count > 0) //如果没有name属性，获取不到file { HttpPostedFile file = httpFileCollection[0];

fileName = Path.GetFileName(file.FileName);

if (File.Exists(serverPath)) { rdsl.returnMessage = "该文件已存在,请更改文件名或者删除原文件,然后上传."; return GetJSON.JSONSerialize(rdsl); }

Thread thread = new Thread(new ThreadStart(() => { file.SaveAs(serverPath); } )); thread.Start();

}                 else                 {                     rdsl.returnCode = iCode.ToString();                     rdsl.returnMessage = "未获取到文件.";
                } return GetJSON.JSONSerialize(rdsl);
            }             catch (Exception ex)             {                 log.Error(ex.Message);                 log.Error(ex.StackTrace);
            }
        }

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/// <summary> /// 下载文件方法 /// </summary> /// <param name="serverPath">被下载的文件地址（服务器地址包括文件）</param> /// <param name="filePath">另存放的路径（本地需要存储文件的文件夹地址）</param> public void Download(string serverPath, string filePath) { WebClient client = new WebClient(); string fileName = serverPath.Substring(serverPath.LastIndexOf("/") + 1); ;//被下载的文件名 string path = filePath + fileName;//另存为地址 try { WebRequest myre = WebRequest.Create(serverPath); } catch (Exception ex) { MessageBox.Show(ex.Message, "Error"); } try { client.DownloadFile(serverPath, fileName); FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.Read); BinaryReader r = new BinaryReader(fs); byte[] mbyte = r.ReadBytes((int)fs.Length); FileStream fstr = new FileStream(path, FileMode.OpenOrCreate, FileAccess.Write); fstr.Write(mbyte, 0, (int)fs.Length); fstr.Close(); } catch (Exception ex) { MessageBox.Show(ex.Message, "Error"); } }