C #: ajax para lograr tres vinculación con los antecedentes de carga

interfaz de front-end

<div>
	<div>
		<select onchange="GetWd(1)" id="province" name="province">
				<option>--请选择--</option>
		</select>
		<select onchange="GetWd(2)" id="city" name="city">
				<option>--请选择--</option>
		</select>
		<select onchange="GetWd(3)" id="area" name="area">
				<option>--请选择--</option>
		</select>
	</div>
		<div id="city_box">

		</div>
</div>

valores de los campos de base de datos

js parte

<script>
				$.ajax({
					type: "post",
					url: "/dev/GetCity.ashx",
					data: {
						action: 'city',
						num: 0,
					},
					success: function(d) {
						var dd = JSON.parse(d);
						$.each(dd.data, function(i, o) {
							$('#province').append('<option value="' + o.sheng + '">' + o.sheng + '</option>');
						});
					}
				})

				function GetWd(num) {
					if(num == 1) {
						var province = $('#province').val();
						if(province != '') {
							$.ajax({
								type: "post",
								url: "/dev/GetCity.ashx",
								data: {
									action: 'city',
									num: num,
									province: province,
								},
								success: function(d) {
									var dd = JSON.parse(d);
									document.getElementById('city').innerHTML = '<option>--请选择--</option>';
									$.each(dd.data, function(i, o) {
										$('#city').append('<option value="' + o.shi + '">' + o.shi + '</option>');
									});
									$('#city_box').html('');
									$.each(dd.datas, function(i, o) {
										$('#city_box').append('<h2>地址：' + o.address + '<br>电话：' + o.tel + '</h2>')
									});
								}
							})
						}
						document.getElementById('city').innerHTML = '<option>--请选择--</option>';
						document.getElementById('area').innerHTML = '<option>--请选择--</option>';
					}
					if(num == 2) {
						var province = $('#province').val();
						var city = $('#city').val();
						if(province != '') {
							if(city != '') {
								$.ajax({
									type: "post",
									url: "/dev/GetCity.ashx",
									data: {
										action: 'city',
										num: num,
										province: province,
										city: city,
									},
									success: function(d) {
										var dd = JSON.parse(d);
										document.getElementById('area').innerHTML = '<option>--请选择--</option>';
										$.each(dd.data, function(i, o) {
											$('#area').append('<option value="' + o.qu + '">' + o.qu + '</option>');
										});
										$('#city_box').html('');
										$.each(dd.datas, function(i, o) {
											$('#city_box').append('<h2>地址：' + o.address + '<br>电话：' + o.tel + '</h2>')
										});
									}
								})
							}
							document.getElementById('area').innerHTML = '<option>--请选择--</option>';
						}
					}
					if(num == 3) {
						var province = $('#province').val();
						var city = $('#city').val();
						var area = $('#area').val();
						if(province != '') {
							if(city != '') {
								if(area != '') {
									$.ajax({
										type: "post",
										url: "/dev/GetCity.ashx",
										data: {
											action: 'city',
											num: num,
											province: province,
											city: city,
											area: area
										},
										success: function(d) {
											var dd = JSON.parse(d);
											$('#city_box').html('');
											$.each(dd.data, function(i, o) {
												$('#city_box').append('<h2>地址：' + o.address + '<br>电话：' + o.tel + '</h2>')
											});
										}
									})
								}
							}
						}
					}
				}
</script>

La ejecución del programa

public void ProcessRequest(HttpContext context)
        {
            context.Response.ContentType = "text/plain";
            string action = context.Request["action"];
            switch (action)
            {
                case "city":
                    GetWd(context);
                    break;
            }
        }

        public void GetWd(HttpContext context)
        {
            int num = int.Parse(context.Request["num"].ToString());
            string province = context.Request["province"];
            string city = context.Request["city"];
            string area = context.Request["area"];
            string sqlStr = "";
            DataTable dt;
            if (num == 0)
            {
                sqlStr = "select sheng from nw_customform_user_fuwuwangdian group by sheng";
                dt = SqlEasy.ExecuteDataTable(sqlStr);
                context.Response.Write("{\"status\":\"0\",\"data\":" + JSONhelper.ToJson(dt, false) + "}");
            }
            if (num == 1)
            {
                sqlStr = "select shi from nw_customform_user_fuwuwangdian where sheng='" + province + "' group by shi";
                dt = SqlEasy.ExecuteDataTable(sqlStr);
                DataTable dts = SqlEasy.ExecuteDataTable("select * from nw_customform_user_fuwuwangdian where sheng='" + province + "'");
                context.Response.Write("{\"status\":\"0\",\"data\":" + JSONhelper.ToJson(dt, false) + ",\"datas\":" + JSONhelper.ToJson(dts, false) + "}");
            }
            if (num == 2)
            {
                sqlStr = "select qu from nw_customform_user_fuwuwangdian where sheng='" + province + "' and shi='" + city + "' group by qu";
                dt = SqlEasy.ExecuteDataTable(sqlStr);
                DataTable dts = SqlEasy.ExecuteDataTable("select * from nw_customform_user_fuwuwangdian where sheng='" + province + "' and shi='" + city + "'");
                context.Response.Write("{\"status\":\"0\",\"data\":" + JSONhelper.ToJson(dt, false) + ",\"datas\":" + JSONhelper.ToJson(dts, false) + "}");
            }
            if (num == 3)
            {
                sqlStr = "select * from nw_customform_user_fuwuwangdian where sheng='" + province + "' and shi='" + city + "' and qu='" + area + "'";
                dt = SqlEasy.ExecuteDataTable(sqlStr);
                context.Response.Write("{\"status\":\"0\",\"data\":" + JSONhelper.ToJson(dt, false) + "}");
            }
        }

página de resultados