錯誤選擇欄最近與ALTER TABLE插入ODP.NET

Question

1-使用Oracle.DataAccess

2-執行一個命令將列添加到表連接到的Oracle XE：改變表TABLE添加塔B INT ;

3-執行命令以選擇此列

4-使用DataReader讀取。應用程序引發IndexOutOfRangeException：無法找到結果指定列設置

5重新啓動應用程序，查詢可以正常運行

DataReader的，爲什麼不能訪問我創建剛纔列？

這裏是一個大而簡單的代碼來測試：

private void button1_Click(object sender, EventArgs e) 
{ 
    using (OracleConnection con = new OracleConnection(Settings.Default.CS)) 
    { 
     con.Open(); 
     try 
     { 
      using (OracleCommand com = new OracleCommand()) 
      { 
       com.Connection = con; 

       // Create a test table 
       com.CommandText = "CREATE TABLE Test (a int)"; 
       com.ExecuteNonQuery(); 

       // Add one column 
       com.CommandText = "ALTER TABLE Test ADD b int"; 
       com.ExecuteNonQuery(); 

       com.CommandText = "SELECT * FROM Test"; 
       using (DbDataReader dr = com.ExecuteReader()) 
       { 
        MessageBox.Show(dr.FieldCount.ToString()); 
        // Here is showing "2", thats ok 
       } 
      } 
     } 
     finally 
     { 
      con.Close(); 
     } 
    } 
} 

private void button2_Click(object sender, EventArgs e) 
{ 
    using (OracleConnection con = new OracleConnection(Settings.Default.CS)) 
    { 
     con.Open(); 
     try 
     { 
      using (OracleCommand com = new OracleCommand()) 
      { 
       OracleTransaction trans = con.BeginTransaction(); 
       try 
       { 
        // Add a column to table already created 
        com.Connection = con; 
        com.CommandText = "ALTER TABLE Test ADD c int"; 
        com.ExecuteNonQuery(); 

        // Insert a value, ok 
        com.CommandText = "INSERT INTO TEST (a, b, c) VALUES (1, 2, 3)"; 
        com.ExecuteNonQuery(); 

        trans.Commit(); 
       } 
       catch 
       { 
        trans.Rollback(); 
        throw; 
       } 

       // Selecting only "c" column 
       com.CommandText = "SELECT c FROM Test"; 
       using (DbDataReader dr = com.ExecuteReader()) 
       { 
        if (dr.Read()) 
         MessageBox.Show(Convert.ToInt32(dr["c"]).ToString()); 
         // Showing correct value, ok 
       } 

       // Uncomment these lines to solve problem 
       //con.Close(); 
       //OracleConnection.ClearAllPools(); 
       //con.Open(); 

       // Selecting all fields * from table 
       com.CommandText = "SELECT * FROM Test"; 
       using (DbDataReader dr = com.ExecuteReader()) 
       { 
        MessageBox.Show(dr.GetSchemaTable().Rows.Count.ToString() + "/" + dr.FieldCount.ToString()); 
        // HERE IS THE PROBLEM: message are showing 2/2, but table haves 3 fields 

        if (dr.Read()) 
         MessageBox.Show(Convert.ToInt32(dr["c"]).ToString()); 
        // Here throws IndexOutOfRangeException: Unable to find specified column in result set 
       } 
      } 
     } 
     finally 
     { 
      con.Close(); 
     } 
    } 
} 

Answer 1

這聽起來像插入事務，當你執行讀者尚未提交。我想，你可以通過關閉您插入，然後再次打開它，你執行了讀者之前剛剛經過的連接進行驗證（您可能需要使用OracleConnection.ClearAllPools）

Answer 2

嘗試使用OracleConnection.BeginTransaction創建一個事務，然後Commit在選擇之前，如文檔中的example所示。