How to return data from web method to fill treegrid

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ASP.NET

treeview

Hi I want to bind easyui treegrid. I hava following data

id  name                 parent
1   C                    NULL
2   Program Files        1
3   WINDOWS              1
4   Microsoft Sql Server 2
5   Microsoft .Net       3

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"
			}]
		}]
	}
	}]
}]