// Create Google Sheets API service.

SheetsService SheetsService = GetSheetsService();

// Here is my doubt.
// I have specified only the sheet name
// but I dont know the range which could be dynamic

var range = "Sheet3!";

SpreadsheetsResource.ValuesResource.GetRequest request =
    SheetsService.Spreadsheets.Values.Get(SpreadSheetID, range);

var response = request.Execute();
return response;