This SqlTransaction has completed; it is no longer usable. โค้ดนี้ใช้งานได้ครับ แต่จะError ในกรณีที่มีการเรียกใช้ Method ซ้ำด้วยObject

public class DBClass
{
    private string STR_CONNECTION = "Server=HOADNA-PC\\SQLEXPRESS;Uid=sa;PASSWORD=123;database=aa;Max Pool Size=400;Connect Timeout=600;";
    private SqlConnection DBConnection;
    private SqlCommand DBCommand;
    private SqlDataAdapter DBAdapter;
    private SqlTransaction Trans = default(SqlTransaction); 

    public DBClass()
    {
        DBConnection = new SqlConnection(STR_CONNECTION);
        DBConnection.Open();
        Trans = DBConnection.BeginTransaction(IsolationLevel.ReadCommitted);
        
        DBCommand = new SqlCommand();
        DBCommand.Connection = DBConnection;
        DBCommand.Transaction = Trans; 
        DBAdapter = new SqlDataAdapter();
        
    }

    public DataSet Query(string strSQL)
    {
        DataSet DS = new DataSet();
        try
        {
            DBCommand.CommandText = strSQL;
            DBAdapter.SelectCommand = DBCommand;
            DBAdapter.Fill(DS);
            Trans.Commit();   //***************************  จุด Error *************************
        }
        catch (Exception Ex)
        {
            Trans.Rollback();
        }
        finally
        {
            DBConnection.Close();
        }
        return DS;
    }
}