首先，如果web方法在页面类中，而不在Webservice类中，则它应该是静态的.

First, it the webmethod is in the page class, and not in a Webservice class, then it should be static.

第二，传输的数据实际上不是字符串，而是对象，因此将其更改为:

Second, the data transfered is not really a string, but an object, so change it to:

var dataString = { 'value':  value  };

第三件事，类型"用于旧版本的jquery，您应该将ajax调用更改为:

Third thing, "type" is for older versions of jquery, you should either change your ajax call to:

method: "GET",
url: pagePath,
data: dataString,
contentType: "application/json; charset=utf-8",
dataType: "json",...

或通过删除

UseHttpGet = true