Question

I am writing C# code and using LINQ and some stored procedures, i am careful about opening and closing the connections but i keep getting this error.

Timeout expired.  
The timeout period elapsed prior to obtaining a connection from the pool.  
This may have occurred because all pooled connections were in use and max pool size was reached.

my code works perfectly except the occurence of this error, what can i do about it?

Thanks for any ideas.

 public static List<int> GetIslemIdleribySPbyCariId(int cariId)
    {
        string connString = System.Configuration.ConfigurationManager.ConnectionStrings["LocalSqlServer1"].ConnectionString;

        SqlConnection sqlConn = new SqlConnection(connString);
        sqlConn.Open();

        List<int> islemidleri = new List<int>();
        islemidleri.Clear();

        SqlCommand cmd;
        cmd = new SqlCommand("GetIslemIdleri", sqlConn);
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.Parameters.Add(new SqlParameter("@CARIID", cariId));

        using (var reader = cmd.ExecuteReader())
        {
            while (reader.Read())
            {
                islemidleri.Add(reader.GetInt32(0));

            }
            cmd.Parameters.Clear();
        }

        sqlConn.Close();

        return islemidleri;

    }
    /// <summary>
    /// SP kullanarak dovizturlerini döndürür
    /// </summary>
    /// <returns>string listesi döndürür için döviz türleri var TL, USD vs.</returns>
    public static List<string> GetDovizTurleribySP()
    {
        string connString = System.Configuration.ConfigurationManager.ConnectionStrings["LocalSqlServer1"].ConnectionString;

        SqlConnection sqlConn = new SqlConnection(connString);
        sqlConn.Open();

        List<string> dovizTanimlari = new List<string>();

        string commandGetDovizTanimlari = "EXEC GetDovizTanimlari";
        SqlCommand cmd;
        cmd = new SqlCommand(commandGetDovizTanimlari, sqlConn);

        using (var reader = cmd.ExecuteReader())
        {
            while (reader.Read())
            {
                dovizTanimlari.Add(reader.GetString(0));
            }

        }
        return dovizTanimlari;

    }

Answer 1

From your code you are not closing the connection in the GetDovizTurleribySP function. I would suggest that you use the using statement to ensure that the connections are closed even if an exception occurs.

It might look something like this

public static List<string> GetDovizTurleribySP()
{
  string connString = System.Configuration.ConfigurationManager.ConnectionStrings["LocalSqlServer1"].ConnectionString;

  using (SqlConnection sqlConn = new SqlConnection(connString))
  {
    sqlConn.Open();

    List<string> dovizTanimlari = new List<string>();

    string commandGetDovizTanimlari = "EXEC GetDovizTanimlari";
    SqlCommand cmd;
    cmd = new SqlCommand(commandGetDovizTanimlari, sqlConn);

    using (var reader = cmd.ExecuteReader())
    {
      while (reader.Read())
      {
        dovizTanimlari.Add(reader.GetString(0));
      }

    }
    return dovizTanimlari;
  }
}