Check Id exists in websevice method content

Hi Friends,

 

I am storing web sevice method Json content into Dictionary object.I am inserting data into sqlserver database Table.When I am running service again previous content need not be inseted into the database.For this I am checking max id of invoic number and looping object and comparing both id's. and again for insertion I am using for each loop.

 

It is correct approach I am doing please tell me the simplest way to do this.

 

Json data :

 

{"Result":{"tblDsr":[{"Store_Name":"S Foods",

"Void_date_Time":"2018-09-23T00:00:00","Invoice_Number":119,"Total_Amount":150.0000,"Total_Tax":0.0000},

{"Store_Name":"S Foods","Void_date_Time":"2018-09-24T00:00:00",

]"Invoice_Number":133,"Total_Amount":220.0000,"Total_Tax":0.0000}]}