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Returns DataTable using async.net 4.0

I have a method that returns datatable. I thought using .net 4.0, I could just asynchronously log in and return the data. But this code returns a null Datatable object. Any ideas what is wrong with this code.

public DataTable GetData(string sql, string connectionName)
{
    DataTable dt = (DataTable)GetDataAsync(sql, connectionName).AsyncState;
    return dt;
}

private async Task<DataTable> GetDataAsync(string sql, string connectionName)
{
    return await TaskEx.Run(() => { return FillData(sql, connectionName); });
}

private DataTable FillData(string sql, string connectionName)
{
    SqlConnection conn = _connections.Where(w => w.ConnectionName == connectionName).Single().Connection;
    SqlDataAdapter adp = new SqlDataAdapter(sql, conn);
    DataSet ds = new DataSet();

    adp.Fill(ds);

    return ds.Tables[0];
}
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3 answers

Firstly, you cannot use async/ awaitwith .NET 4 or C # 4. This is a new feature in C # 5. There were CTPs that were installed on top of .NET 4, but there are certain errors in these CTPs - do not use them. You should use the full version of .NET 4.5, which includes the C # 5 compiler. (All this in Visual Studio 2012.)

-, , . Result - , Task<T>.

-, Result , , . :

public DataTable GetData(string sql, string connectionName)
{
    DataTable dt = (DataTable)GetDataAsync(sql, connectionName).Result;
    return dt;
}

... :

public DataTable GetData(string sql, string connectionName)
{
    return FillData(sql, connectionName);
}

, .

+9

.

public static async Task<DataTable> GetDataTableAsync(this System.Data.Common.DbCommand command, CancellationToken cancellationToken, string tableName = null)
    {
        TaskCompletionSource<DataTable> source = new TaskCompletionSource<DataTable>();
        var resultTable = new DataTable(tableName ?? command.CommandText);
        DbDataReader dataReader = null;

        if (cancellationToken.IsCancellationRequested == true)
        {
            source.SetCanceled();

            await source.Task;
        }

        try
        {
            await command.Connection.OpenAsync();
            dataReader = await command.ExecuteReaderAsync(CommandBehavior.Default);
            resultTable.Load(dataReader);
            source.SetResult(resultTable);
        }
        catch (Exception ex)
        {
            source.SetException(ex);
        }
        finally
        {
            if (dataReader != null)
                dataReader.Close();

            command.Connection.Close();
        }

        return resultTable;
    }
+8

async, . , , Async Targeting Pack, Async CTP.

private async Task<DataTable> GetDataAsync(string sql, string connectionName)
{
  return await TaskEx.Run(() => { return FillData(sql, connectionName); });
}

private async GetAndProcessDataAsync()
{
  DataTable table = await GetDataAsync("my sql", "my connection name");
  ProcessData(table);
}
+2

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