前端：

引用以下两个js文件

<script type="text/javascript" src="https://www.idaobin.com/test/jquery-3.2.1.js"></script>
<script type="text/javascript" src="https://www.idaobin.com/test/ajaxfileupload.js"></script>

js：

<script type="text/javascript">
        $(function () {  //文件类型判断
            $("#up").click(function () {
                var location = $("input[name='file']").val(); 
                var point = location.lastIndexOf("."); 
                var type = location.substr(point).toLowerCase();
                var uploadFiles = document.getElementById("file1").files;
                var size = $("#file1")[0].files[0].size; 
                if (uploadFiles.length == 0) {
                    alert("请选择要上传的文件");
                }
                else if((size/1024/1024)>1){
                    alert("超过文件上传限制");
                }
                else if (type == ".zip" || type == ".rar") {
                    ajaxFileUpload();
                }
                else {
                     alert("只允许上传.zip或者.rar格式的文件");
                } 
            });
        });

        function ajaxFileUpload() {
            $.ajaxFileUpload(
                {
                    url: '/upload.aspx', //用于文件上传的服务器端请求地址
                    secureuri: false, //是否需要安全协议，一般设置为false
                    fileElementId: 'file1', //文件上传域的ID
                    dataType: 'json', //返回值类型 一般设置为json
                    success: function (data, status)  //服务器成功响应处理函数
                    {
                        console.log(data.msg);
                        if (typeof (data.error) != 'undefined') {
                            if (data.error != '') {
                                alert(data.error);
                            } else {
                                alert(data.msg);
                            }
                        }
                    },
                    error: function (data, status, e)//服务器响应失败处理函数
                    {
                        alert(e);
                    }
                }
            );
            return false;
        }
    </script>

注意：url: ‘/upload.aspx’的upload.aspx为上传的处理页面，也可以是一般程序处理类

html：

<p><input type="file" id="file1" name="file" /></p>
<input type="button" id="up" value="上传" />

后端

upload.aspx.cs：

protected void Page_Load(object sender, EventArgs e)
        {
            HttpFileCollection files = Request.Files;
            string msg = string.Empty;
            string error = string.Empty;
            if (files.Count > 0)
            {
                string director = Server.MapPath("/uploads/"); //上传目录
                if (!Directory.Exists(director))
                {
                    Directory.CreateDirectory(director);
                }
                string path = director + Path.GetFileName(files[0].FileName);
                if (File.Exists(path))
                {
                    msg = "上传失败，文件存在";
                }
                if((files[0].ContentLength / 1000) > 1024000){
                   msg = "文件大小超过限制";
                }

                else
                {
                    files[0].SaveAs(path);
                    //返回json数据
                    msg = "上传成功";
                }
                string res = "{ error:'" + error + "', msg:'" + msg + "'}";
                Response.Write(res);
                Response.End();
            }
        }

Web.config文件上传大小限制

放在<configuration>标签下面

<system.webServer>
        <security>
        <requestFiltering >
          <requestLimits maxAllowedContentLength ="1073741824"></requestLimits>
        </requestFiltering>
      </security>
</system.webServer>

放在<system.web>标签内 

<httpRuntime maxRequestLength="1073741824" appRequestQueueLimit ="100"  executionTimeout="3600" useFullyQualifiedRedirectUrl="true" requestValidationMode="2.0" /> 

原文链接：https://www.idaobin.com/archives/1922.html

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