I was trying to make an Oracle query with the async/await .NET feature. The result set is pretty large and takes about 5-10 seconds to come back. The Window_Loaded is hanging the UI thread, essentially I wanted to use async/wait to do the query in the background and then update a dataview with the result.
So is this an Oracle driver issue or a code error? E.g. is something here being done synchronously instead of asynchronously? I'm using the latest Oracle.ManagedDataAccess I could get from Oracle's web-site.
async Task<DataTable> AccessOracleAsync()
{
DataTable dt;
using(OracleConnection conn = new OracleConnection(ConfigurationManager
.ConnectionStrings["connStr"].ConnectionString))
using (OracleCommand cmd = new OracleCommand(@"SELECT * FROM myTbl", conn))
{
await conn.OpenAsync();
using (var reader = await cmd.ExecuteReaderAsync())
{
dt = new DataTable();
dt.Load(reader);
}
}
return dt;
}
private async void Window_Loaded(object sender, RoutedEventArgs e)
{
await AccessOracleAsync();
}
I tried this, and it is still blocking the UI:
async Task<DataView> AccessOracleAsync()
{
DataTable dt;
using (OracleConnection conn = new OracleConnection(ConfigurationManager
.ConnectionStrings["connStr"].ConnectionString))
using (OracleCommand cmd = new OracleCommand(@"SELECT * FROM myTbl", conn))
{
await conn.OpenAsync().ConfigureAwait(false);
using (DbDataReader reader = await cmd.ExecuteReaderAsync().ConfigureAwait(false))
{
dt = new DataTable();
await Task.Run(() => dt.Load(reader)).ConfigureAwait(false);
}
}
return dt.AsDataView();
}
private async void Window_Loaded(object sender, RoutedEventArgs e)
{
Data1.ItemsSource = await AccessOracleAsync();
}
So in the end, I changed the method to something like this to make it not block. It appears I had the right idea, just that the Oracle managed library implemented the Async methods synchronously (only to comply with the interface).
private async Task<DataView> AccessOracleAsync()
{
DataTable dt = new DataTable();
using (OracleConnection conn = new OracleConnection(ConfigurationManager
.ConnectionStrings["connStr"].ConnectionString))
using (OracleCommand cmd = new OracleCommand(@"SELECT * myTbl", conn))
{
await Task.Run(() =>
{
conn.Open();
using (DbDataReader reader = cmd.ExecuteReader())
{
dt.Load(reader);
}
}).ConfigureAwait(false);
}
return dt.AsDataView();
}
