How to return data from web method to fill treegrid

 

 

 how can I return a string in the following format from web method

 

[{ 	"id":1, 	"name":"C", 	"children":[{ 		"id":2, 		"name":"Program Files", 		"children":[{ 			"id":4, 			"name":"Microsoft Sql Server", 			}] 		},{ 			"id":3, 			"name":"WINDOWS", 			"children":[{ 				"id":5, 				"name":"Microsoft .Net" 			}] 		}] 	} 	}] }]