1.webservice方法

 [System.Web.Script.Services.ScriptService]
    public class TestService : System.Web.Services.WebService
    {

        [WebMethod]
        public string Test(string inputStr)
        {
            ////HttpContext.Current.Response.AddHeader("Access-Control-Allow-Origin", "*");
            return "Hello :"+inputStr;
        }
    }

2.webservice网站web.config配置

<?xml version="1.0" encoding="utf-8"?>

<!--
  有关如何配置 ASP.NET 应用程序的详细信息，请访问
  http://go.microsoft.com/fwlink/?LinkId=169433
  -->

<configuration>
    <system.web>
      <compilation debug="true" targetFramework="4.0" />
      <customErrors mode="Off"/>
      <webServices>
        <protocols>
          <add name="HttpSoap"/>
          <add name="HttpPost"/>
          <add name="HttpGet"/>
          <add name="Documentation"/>
        </protocols>
      </webServices>
    </system.web>
  <system.webServer>
    <httpProtocol>
      <customHeaders>
        <add name="Access-Control-Allow-Methods" value="OPTIONS,POST,GET"/>
        <add name="Access-Control-Allow-Headers" value="x-requested-with,content-type"/>
        <add name="Access-Control-Allow-Origin" value="*" />
      </customHeaders>
    </httpProtocol>
  </system.webServer>

</configuration>

图中框出的2块经测试 缺一不可

3.jquery ajax调用

function doClick1() {

　　　　　　jQuery.support.cors = true; //IE10以下

        $.ajax({
            type: "post",
            url: "http://xx.com/TestService.asmx/Test",
            dataType: ‘xml‘,
            data: { inputStr: ‘everyone‘ },
            success: function (data) {
                alert(data); //xml对象
            },
            error: function (XMLHttpRequest, textStatus, errorThrown) {
                console.log(XMLHttpRequest);
                alert(‘error:‘ + errorThrown);
            }
        });
    }

From:  http://www.cnblogs.com/xuejianxiyang/p/5369346.html