private static IEnumerable <T> internalQuery <T>(this IDbConnection conn, CommandDefinition command)
{
// 缓存
var parameter = command.Parameters;
Certificate certificate = new Certificate(command.CommandText, command.CommandType, conn, typeof(T), parameter?.GetType());
CacheInfo cacheInfo = CacheInfo.GetCacheInfo(certificate, parameter);
// 读取
IDbCommand cmd = null;
IDataReader reader = null;
var wasClosed = conn.State == ConnectionState.Closed;
try {
cmd = command.SetupCommand(conn, cacheInfo.ParameterReader);
if (wasClosed)
{
conn.Open();
}
reader = ExecuteReaderWithFlagsFallback(cmd, wasClosed, CommandBehavior.SingleResult);
if (cacheInfo.Deserializer == null)
{
cacheInfo.Deserializer = BuildDeserializer <T>(reader);
}
while (reader.Read())
{
var val = cacheInfo.Deserializer(reader);
yield return(GetValue <T>(val));
}
} finally {
// dispose
if (reader != null)
{
if (!reader.IsClosed)
{
try {
cmd.Cancel();
} catch {
}
}
reader.Dispose();
}
if (wasClosed)
{
conn.Close();
}
cmd?.Dispose();
}
IDataReader ExecuteReaderWithFlagsFallback(IDbCommand c, bool close, CommandBehavior behavior)
{
try {
return(c.ExecuteReader(GetBehavior(close, behavior)));
} catch (ArgumentException ex) {
throw;
}
}
CommandBehavior GetBehavior(bool close, CommandBehavior @default)
{
return(close ? (@default | CommandBehavior.CloseConnection) : @default);
}
}