NSString urlstring = new NSString("http://211.155.229.230:8585/api/users/postregister"); 
            NSMutableUrlRequest request = new NSMutableUrlRequest(new NSUrl(urlstring));
            request.Url = new NSUrl(urlstring);
            request.HttpMethod = "POST";

NSUrlConnection connection = new NSUrlConnection(request, new ConnectionDelegate((response) =>
                {
                    //解析数据
                    JsonValue jsonObj = JsonValue.Parse(response); 
                }));
       ////ConnectionDelegate

using System;
using Foundation;
using System.Text;

namespace XinPeiOA
{
    public class ConnectionDelegate : NSUrlConnectionDataDelegate
    {
        public ConnectionDelegate()
        {
        }
        private Action<string> finishedCallback;
        private StringBuilder responseData;
        //构造方法
        public ConnectionDelegate(Action<string> callback)
        {
            this.finishedCallback = callback;
            this.responseData = new StringBuilder();
        }
        //结束数据后的相关操作
        public override void ReceivedData(NSUrlConnection connection, NSData data)
        {
            //判断数据是否存储
            if (null != data)
            {
                this.responseData.Append(data.ToString());
            }
        }
        ///当请求结束后的相关操作
        public override void FinishedLoading(NSUrlConnection connection)
        {
            if (null != this.finishedCallback)
            {
                this.finishedCallback(this.responseData.ToString());
            }
            this.responseData.Clear();
        }

//当请求失败时的相关操作
        public override void FailedWithError(NSUrlConnection connection, NSError error)
        {
            //判断是否有错误
            if (null != error)
            {
                Console.WriteLine("Error in connection! { 0}", error.LocalizedDescription);
            }
        }

}
}