@Sadakat,

ASMX will not return JSON data its XML, SVC will return JSON data.

Select Insert Edit Update Delete using WCF Service in ASP.Net using C# and VB.Net

Select Insert Edit Update Delete using Web Service in ASP.Net

Now you have the reference articles, but please don't expect us to write code for you as per your requirement.

Thus please refer the articles and start programming and if any problem let is know.