Question

Normaly我会使用“Using”或者只使用connection.open（）和connection.close（）。但是当我调用存储过程时，不需要这样做。怎么会？（是的，下面的codesnippit无需使用或打开即可使用）。

try {
    SqlCommand cmd = new SqlCommand("***", connectionSiteDb);
    DataTable dt = new DataTable();
    cmd.CommandType = CommandType.StoredProcedure;
    cmd.Parameters.Add(new SqlParameter("@ProcessSegmentID", ProcessSSegmentID));
    cmd.Parameters.Add(new SqlParameter("@PO_RecipeID", PO_RecipeID));
    cmd.Parameters.Add(new SqlParameter("@ProductSegmentVersion", ProductSegmentVersion));


    SqlDataAdapter da = new SqlDataAdapter();
    da.SelectCommand = cmd;
    da.Fill(dt);
    return dt;
}
catch (Exception e) {
     Console.WriteLine(e);
     return null;
}

Answer 1

是否使用using statement取决于CommandType是Text还是StoredProcedure。

SqlDataAdapter.Fill会自行打开连接。

来自Populating a DataSet from a DataAdapter

Fill方法隐式打开DataAdapter的Connection 如果发现连接尚未打开，则使用。如果填写打开连接，它也将在Fill时关闭连接完了。这可以在处理单个代码时简化代码填充或更新等操作。

另外DbDataAdapter.Fill(DataTable)

在与SELECT语句关联的连接对象必须有效， 但不需要打开。如果之前连接已关闭调用Fill，打开它以检索数据，然后关闭。如果在调用Fill之前连接已打开，它仍保持打开状态。

由于SqlDataAdapter未实现IDisposable，因此您无需在其中使用using语句。

如果您想深入了解，可以查看QuietClose method和QuietOpen method实施;

static private void QuietClose(IDbConnection connection, ConnectionState originalState)
{
      // close the connection if:
      // * it was closed on first use and adapter has opened it, AND
      // * provider's implementation did not ask to keep this connection open
      if ((null != connection) && (ConnectionState.Closed == originalState)) {
          // we don't have to check the current connection state because
          // it is supposed to be safe to call Close multiple times
          connection.Close();
      }
}

// QuietOpen needs to appear in the try {} finally { QuietClose } block
// otherwise a possibility exists that an exception may be thrown, i.e. ThreadAbortException
// where we would Open the connection and not close it
static private void QuietOpen(IDbConnection connection, out ConnectionState originalState)
{
     originalState = connection.State;
     if (ConnectionState.Closed == originalState) {
         connection.Open();
     }
}

调用存储过程时需要Connection.Open（）吗？

1 个答案: