DataSet and datatable with LinQ

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C#

Hi I have created a dictionary.I need to fetch query from my database using LINQ and add it to the datatable..then I need to loop through the datatable get the results and store it in the dictionary..I need to know how to add the data to the dattable..below is my part of the code

public static void fetchdata()
       {
           string USER_ID="AH01"
         
            northwinddatacontext nc= new northwinddatacontext();//datacontext where I have added my table called username

            Dictionary<string,> types = new Dictionary<string,>();
            DataTable dt = new DataTable();

            var result =      from x in nc.usernames
                        	where (x.userId == USER_ID) 
                       		 select x
                       				
             dt=Common.LINQToDataTable(result);

            foreach (DataRow row in dt.Rows)
            {
                nwind nw = new nwind ();
                nw.userID = row.Field<string>("userID").ToString();
                types .Add(nw.userID, nw);
               

            }
          
       }</string>