連線保持開啟時存在的臨時表

當臨時表由其自身建立時，它將在連線開啟時保留。

// Widget has WidgetId, Name, and Quantity properties
public async Task PurchaseWidgets(IEnumerable<Widget> widgets)
{
    using(var conn = new SqlConnection("{connection string}")) {
        await conn.OpenAsync();

        await conn.ExecuteAsync("CREATE TABLE #tmpWidget(WidgetId int, Quantity int)");

        // populate the temp table
        using(var bulkCopy = new SqlBulkCopy(conn)) {
            bulkCopy.BulkCopyTimeout = SqlTimeoutSeconds;
            bulkCopy.BatchSize = 500;
            bulkCopy.DestinationTableName = "#tmpWidget";
            bulkCopy.EnableStreaming = true;

            using(var dataReader = widgets.ToDataReader())
            {
                await bulkCopy.WriteToServerAsync(dataReader);
            }
        }

        await conn.ExecuteAsync(@"
            update w
            set Quantity = w.Quantity - tw.Quantity
            from Widgets w
                join #tmpWidget tw on w.WidgetId = tw.WidgetId");
    }
}