使用Statement和ADO.NET对象(using Statement And ADO.NET Objects)

 考虑以下方法...... 
 
private string[] GetExistingPOWSNumbers()
{
    using (
        var OleAdapter =
            new OleDbDataAdapter(
                "SELECT DISTINCT con_num FROM `Items` WHERE con_num LIKE 'POWS%'",
                ConfigurationManager.ConnectionStrings["MPOleConnectionString"].ConnectionString))
    using (var POWSTable = new DataTable())
    {
        OleAdapter.SelectCommand.Connection.Open();
        OleAdapter.Fill(POWSTable);
        return POWSTable.AsEnumerable().Select(row => Convert.ToString(row["con_num"])).ToArray();
    }
}
 
 是否所有ADO.NET对象都被及时处理？ 我在整个项目中都使用这种方法，当在一次操作中有很多这样的调用时，我收到“Out of Memory”错误。 
 
 编辑：经过一些个人调查后，我发现，实际上，适配器的using语句也不会关闭提供的集合。 我做了以下改变。 现在我使用DataReader而不是填充DataTable。 
 
private string[] GetExistingPOWSNumbers()
{
    var Results = new List<string>();
    using (var OleConnection = new OleDbConnection(ConfigurationManager.ConnectionStrings["MPOleConnectionString"].ConnectionString))
    using (
        var OleCommand =
            new OleDbCommand(
                "SELECT DISTINCT con_num FROM `Items` WHERE con_num LIKE 'POWS%'",
                OleConnection))
    {
        OleConnection.Open();
        using (var OleReader = OleCommand.ExecuteReader(CommandBehavior.CloseConnection))
        {
            if (OleReader == null) return new string[0];
            while (OleReader.Read())
            {
                Results.Add(OleReader.GetString(0));
            }
        }
    }
    return Results.ToArray();
}

Consider the following method...
 
private string[] GetExistingPOWSNumbers()
{
    using (
        var OleAdapter =
            new OleDbDataAdapter(
                "SELECT DISTINCT con_num FROM `Items` WHERE con_num LIKE 'POWS%'",
                ConfigurationManager.ConnectionStrings["MPOleConnectionString"].ConnectionString))
    using (var POWSTable = new DataTable())
    {
        OleAdapter.SelectCommand.Connection.Open();
        OleAdapter.Fill(POWSTable);
        return POWSTable.AsEnumerable().Select(row => Convert.ToString(row["con_num"])).ToArray();
    }
}
 
Are all the ADO.NET objects promptly being disposed of? I am using this method throughout my projects and when there are A LOT of calls like these being made during a single action, I receive "Out of Memory" errors.
 
EDIT: After some personal investigation I discovered that, in fact, the using statement for the adapter DOES NOT also close the provided collection. I made the following change. Now I am using a DataReader instead of populating a DataTable.
 
private string[] GetExistingPOWSNumbers()
{
    var Results = new List<string>();
    using (var OleConnection = new OleDbConnection(ConfigurationManager.ConnectionStrings["MPOleConnectionString"].ConnectionString))
    using (
        var OleCommand =
            new OleDbCommand(
                "SELECT DISTINCT con_num FROM `Items` WHERE con_num LIKE 'POWS%'",
                OleConnection))
    {
        OleConnection.Open();
        using (var OleReader = OleCommand.ExecuteReader(CommandBehavior.CloseConnection))
        {
            if (OleReader == null) return new string[0];
            while (OleReader.Read())
            {
                Results.Add(OleReader.GetString(0));
            }
        }
    }
    return Results.ToArray();
}

原文：https://stackoverflow.com/questions/37122443