Visual Studio 2017

PM Install-Package GeetestSdkCore

	using System;
	using System.Collections.Generic;
	using System.Linq;
	using System.Web;
	using System.Web.UI;
	using System.Web.UI.WebControls;
	using GeetestSDK;

	namespace demo
	{
	    public partial class GetCaptcha : System.Web.UI.Page
	    {
	        protected void Page_Load(object sender, EventArgs e)
	        {
	            Response.ContentType = "application/json";
	            Response.Write(getCaptcha());
	            Response.End();
	        }
	        private String getCaptcha()
	        {
	            GeetestLib geetest = new GeetestLib(GeetestConfig.publicKey, GeetestConfig.privateKey);
	            Byte gtServerStatus = geetest.preProcess();
	            Session[GeetestLib.gtServerStatusSessionKey] = gtServerStatus;
	            return geetest.getResponseStr();
	        }
	    }
	}