public async Task <byte[]> ReadImageBufferAsync(int x, int y, int zoomLevel) { byte[] imageBuffer = null; try { using (var command = new SQLiteCommand("select tile_data from tiles where zoom_level=@z and tile_column=@x and tile_row=@y", connection)) { command.Parameters.AddWithValue("@z", zoomLevel); command.Parameters.AddWithValue("@x", x); command.Parameters.AddWithValue("@y", (1 << zoomLevel) - y - 1); imageBuffer = await command.ExecuteScalarAsync() as byte[]; } } catch (Exception ex) { Debug.WriteLine("MBTileData: {0}/{1}/{2}: {3}", zoomLevel, x, y, ex.Message); } return(imageBuffer); }
// Some day, Microsoft will deign it useful to add async service initializers and we can // bring this code back to the light of day. #if false private async Task <bool> CheckExistingDbAsync(DbConnection db, CancellationToken cancel) { try { // Check for correct structure using (var cmd = new DbCommand(@"SELECT COUNT(*) from sqlite_master", db)) { var result = (long)await cmd.ExecuteScalarAsync(cancel); // We are expecting two tables and one additional index if (result != 3) { _logger.LogWarning("Incorrect/incompatible existing cache db structure found!"); return(false); } } // Check for correct version using (var cmd = new DbCommand(@"SELECT value FROM meta WHERE key = ""version""", db)) { var result = (long)await cmd.ExecuteScalarAsync(cancel); if (result != SchemaVersion) { _logger.LogWarning("Existing cache db has unsupported schema version {SchemaVersion}", result); return(false); } } } catch (Exception ex) { _logger.LogError(ex, "Error while checking compatibilty of existing cache db!"); return(false); } return(true); }
/// <summary> /// Tests the connection asynchronously. /// </summary> /// <returns></returns> public override async Task TestConnectionAsync() { using (var con = await CreateConnectionAsync()) using (var cmd = new SQLiteCommand("SELECT 1", con)) await cmd.ExecuteScalarAsync(); }
/// <summary> /// Tests the connection asynchronously. /// </summary> /// <returns></returns> public override async Task TestConnectionAsync() { using (var con = await CreateConnectionAsync()) using (var cmd = new SQLiteCommand("SELECT 1", con)) await cmd.ExecuteScalarAsync(); }