c# - 事务化时 CommandText 属性未正确初始化错误

Question

此代码之前运行良好。然而，我需要事务化我的读写，当我试图通过事务化我的读取来开始该过程时，我遇到了这个 commandText 未初始化的错误。

确切错误，第 156 行是 DA.Fill(tbl);

Error: System.InvalidOperationException: The CommandText property has not been properly initialized.
   at MySql.Data.MySqlClient.ExceptionInterceptor.Throw(Exception exception)
   at MySql.Data.MySqlClient.MySqlConnection.Throw(Exception ex)
   at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior behavior)
   at MySql.Data.MySqlClient.MySqlCommand.ExecuteDbDataReader(CommandBehavior behavior)
   at System.Data.Common.DbCommand.System.Data.IDbCommand.ExecuteReader(CommandBehavior behavior)
   at System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset, DataTable[] datatables, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior)
   at System.Data.Common.DbDataAdapter.Fill(DataTable[] dataTables, Int32 startRecord, Int32 maxRecords, IDbCommand command, CommandBehavior behavior)
   at System.Data.Common.DbDataAdapter.Fill(DataTable dataTable)
   at MDB_N2000.DatabaseManager.GetTable(TableQuery query) in C:\Users\Tcordeau.pub\DocumentsException thrown: 'System.InvalidOperationException' in MySql.Data.dll
\MDB-N2000\MDB-N2000\Model\DatabaseManager.cs:line 156 The CommandText property has not been properly initialized.

1. 调用 LoadTable。

   public void LoadTable()
   {
       if (Db.IsConnOpen)
       {
           Db.BeginTransaction();
           // Persist the selected row across table reload by keeping track of the row's first value.
           // For this to work, tables need to always have an autonumbered integer index in the first column.
           // Store the row index.
           if (Vals.Any())
               if (Vals[0].Val != null)
                   if (Vals[0].Val.GetType() == typeof(int))
                       RowID = Vals[0].Val;
   
           // For tables in the sub-tables viewer, get the key value of the main table of the module
           // to use as a parameter in the SQL select query.
           if (!IsMainTable)
           {
               LoadTableQuery.Prms[0].Val = MainVM.Modules.SelectedModule.Vwr.Table.Vals[0].Val;
           }
   
           // Get the table from the database
           Tbl = Db.GetTable(LoadTableQuery);
           DataTable MainTable = Db.GetTable(LoadTableQuery);
           MainTable.TableName = "MainTable";
           dv.Table = MainTable;
   
           // Retrieve the row index and set the selected row.
           if (Vals.Any())
               if (Vals[0].Val != null)
                   if (Vals[0].Val.GetType() == typeof(int))
                       Tbl.DefaultView.Sort = Tbl.Columns[0].ColumnName.ToString();
           //SelectedRowIndex = Tbl.DefaultView.Find(RowID);
           Db.CommitTransaction();
       }
   }
   

2. 转到 GetTable。

   public DataTable GetTable(TableQuery query)
   {
       DataTable tbl = new DataTable();
       if (IsConnOpen)
       {
           try
           {
               SelectCmd.Parameters.Clear();
               SelectCmd.CommandText = query.Qry;
               for (int i = 0; i < query.Prms.Count; i++)
               {
                   SelectCmd.Parameters.AddWithValue(query.Prms[i].Col, query.Prms[i].Val);
               }
               // DA = MySQLDataAdapter
               DA.Fill(tbl);
               tbl.DefaultView.Sort = tbl.Columns[0].ColumnName.ToString() + " ASC";
   
           }
           catch (MySqlException ex)
           {
               Msg = "Error: " + ex.Number + " " + ex.Message + " from Qry = " + query.Qry;
           }
           catch (Exception ex)
           {
               Msg = "Error: " + ex + " " + ex.Message;
           }
       }
       else
       {
           Msg = "Not Connected";
       }
       return tbl;
   }
   

我之前已经将查询打印到控制台以确保它不是空白的。

引用方法。

    private DatabaseManager()
    {
        Acct = new Account();

        SelectCmd = new MySqlCommand() { Connection = Conn };
        UpdateCmd = new MySqlCommand() { Connection = Conn };
        Cmd = new MySqlCommand() { Connection = Conn };
        DA = new MySqlDataAdapter(SelectCmd)
        {
            UpdateCommand = UpdateCmd
        };

        Msg = "Ready to Connect";
    }

    // Creates a new transaction and returns the command it's attached to.
    public void BeginTransaction()
    {
        SelectCmd = Conn.CreateCommand();
        MySqlTransaction NewTransaction = Conn.BeginTransaction();
        SelectCmd.Connection = Conn;
        SelectCmd.Transaction = NewTransaction;
    }

    //rollsback transaction
    public void RevertTransaction()
    {
        Cmd.Transaction.Rollback();
    }

    //adds a query to the transaction
    public void TransactionQuery(TableQuery NewQuery)
    {
        Cmd.CommandText = NewQuery.Qry;
        Cmd.ExecuteNonQuery();
    }

    //commits transaction
    public void CommitTransaction()
    {
        SelectCmd.Transaction.Commit();
    }

Answer 1

问题/解决方案是删除这一行

public void BeginTransaction()
{
   // SelectCmd = Conn.CreateCommand();  //Problem Line
    MySqlTransaction NewTransaction = Conn.BeginTransaction();
    SelectCmd.Connection = Conn;
    SelectCmd.Transaction = NewTransaction;
}