MS Dynamics Custom workflow using c# - With input parameters

using System;
using Microsoft.Xrm.Sdk;
using Microsoft.Xrm.Sdk.Workflow;
using System.Activities;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;

namespace SendPolicyAttachment
{
    public class EmailPolicyAttachment : CodeActivity
    {

        [Input("contact")]
        [ReferenceTarget("contact")]
        public InArgument<EntityReference> customer { get; set; }

        [Input("quoteNo")]
        public InArgument<string> quoteNo { get; set; }

        protected override void Execute(CodeActivityContext context)
        {
            ITracingService _traceservice = context.GetExtension<ITracingService>();

            //Create the context
            IWorkflowContext _context = context.GetExtension<IWorkflowContext>();
            IOrganizationServiceFactory _servicefactory = context.GetExtension<IOrganizationServiceFactory>();
            IOrganizationService _service = _servicefactory.CreateOrganizationService(_context.UserId);

            try
            {
                Guid recordId = _context.PrimaryEntityId;

                EntityReference contactId = customer.Get<EntityReference>(context);
                Guid contId = contactId.Id;               

                _traceservice.Trace(contId.ToString());
                string quote = quoteNo.Get<string>(context);

                _traceservice.Trace(quote);

                string strurl = String.Format("{api URL}");

                _traceservice.Trace(strurl);
                WebRequest requestobj = WebRequest.Create(strurl);
                requestobj.Method = "GET";
                requestobj.ContentType = "application/json";

                using (WebResponse response = requestobj.GetResponse())
                {
                    using (var sr = new StreamReader(response.GetResponseStream()))
                    {
                        string result = sr.ReadToEnd();
                        _traceservice.Trace(result);
                    }
                }
            }
            catch (Exception ex)
            {

                throw new InvalidPluginExecutionException(ex.Message) ;
            }
           
        }


    }
}