public class DataBase : Page
{

    protected static readonly ILog log = LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

    protected static string ConnectionString;

    public DataBase()
    {
        ConnectionString = GetConnectionString();
    }

    public static String GetConnectionString()
    {
        return ConfigurationManager.ConnectionStrings["abc"].ConnectionString;
    }

    public static T GetValue<T>(string query)
        where T : IComparable, IConvertible, IEquatable<T>
    {
        Object value = GetValue(query);
        if (Convert.IsDBNull(value))
            return GetDefaultValue<T>();
        return (T)Convert.ChangeType(value, typeof(T));
    }

    public static T GetDefaultValue<T>()
        where T : IComparable, IConvertible, IEquatable<T>
    {
        if (typeof(T) == typeof(String))
            return (T)(object)String.Empty;
        return default(T);
    }

private static Object GetValue(string query)
    {
        try
        {
            using (SqlConnection connection = new SqlConnection(ConnectionString))
            using (SqlCommand command = new SqlCommand(query, connection))
            {
                connection.Open();
                return command.ExecuteScalar();
            }
        }
        catch (Exception e)
        {
            LogQueryError(query, e);
            return DBNull.Value;
        }
    }

protected static void LogQueryError(string query, Exception e)
    {
        log.Error(string.Format("Error while executing Query ({0}): {1}", query, e.Message));
    }
}