SQL Server Database is not updated via C# Code
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I am performing record update operation . my update operation is happening fine but database is not updating values . below is update code. 

            SupPartEntityVal supplypart = new SupPartEntityVal();
            
            String sNum = sNumText.Text;
            String sName = sNameText.Text;
            String sStatus = sText.Text;
            String sCity = cText.Text;
            int rowIndex = int.Parse(rIndex.Text);

            ObjectQuery<S> supply = supplypart.S;
            var query =
            from product in supply
            select new { product.SNUM, product.SNAME, product.STATUS, product.CITY };
            S sup = supplypart.S.Single(product => product.SNUM == sNum);
            sup.SNAME = sName; sup.STATUS = short.Parse(sStatus); sup.CITY = sCity;
           
            this.supplypart.SaveChanges();

1. After making changes, I can see updated value on UI
2. After I close an application, reopen again I can see updated value on UI 
3. Close Visual studio, reopen the application and run it again. 
4. I do not see changes in database. 

am i missing something???  