如何在給定DbCommand或DbConnection的情況下創建DbDataAdapter？

Question

我想創建一個適用於任何數據提供者的數據訪問層。

我知道可以使用連接上可用的工廠方法創建一個DbCommand。

objDbCon.CreateCommand(); 

但是，我找不到任何東西來創建DbDataAdapter。這是ADO.NET中的錯誤還是什麼？

Answer 1

DbProviderFactory.CreateDataAdapter *

您也可以通過DbProviderFactories類獲得已註冊的DbProviders。

*我認爲這是一個錯誤的地方這種方法。

Answer 2

儘管謝爾蓋回答得很好，但我花了一段時間纔將其翻譯成我自己的需求。所以我的理解是，如果你有一個的DbConnection但知道你用引擎蓋下的SqlClient你的代碼看起來是這樣的：

DbDataAdapter da = DbProviderFactories.GetFactory("System.Data.SqlClient").CreateDataAdapter(); 

Answer 3

既然你不知道你給出的連接類型。 NET沒有提供解決問題的好方法。下面是我們使用：

/// <summary> 
/// Construct a DataAdapater based on the type of DbConnection passed. 
/// You can call connection.CreateCommand() to create a DbCommand object, 
/// but there's no corresponding connection.CreateDataAdapter() method. 
/// </summary> 
/// <param name="connection"></param> 
/// <exception>Throws Exception if the connection is not of a known type.</exception> 
/// <returns></returns> 
public static DbDataAdapter CreateDataAdapter(DbConnection connection) 
{ 
    //Note: Any code is released into the public domain. No attribution required. 

    DbDataAdapter adapter; //we can't construct an adapter directly 
     //So let's run around the block 3 times, before potentially crashing 

    if (connection is System.Data.SqlClient.SqlConnection) 
     adapter = new System.Data.SqlClient.SqlDataAdapter(); 
    else if (connection is System.Data.OleDb.OleDbConnection) 
     adapter = new System.Data.OleDb.OleDbDataAdapter(); 
    else if (connection is System.Data.Odbc.OdbcConnection) 
     adapter = new System.Data.Odbc.OdbcDataAdapter(); 
    else if (connection is System.Data.SqlServerCe.SqlCeConnection) 
     adapter = new System.Data.SqlServerCe.SqlCeDataAdapter(); 
    else if (connection is Oracle.ManagedDataAccess.Client.OracleConnection) 
     adapter = new Oracle.ManagedDataAccess.Client.OracleDataAdapter(); 
    else if (connection is Oracle.DataAccess.Client.OracleConnection) 
     adapter = new Oracle.DataAccess.Client.OracleDataAdapter(); 
    else if (connection is IBM.Data.DB2.DB2Connection) 
     adapter = new IBM.Data.DB2.DB2DataAdapter(); 
    //TODO: Add more DbConnection kinds as they become invented 
    else 
    { 
     throw new Exception("[CreateDataAdapter] Unknown DbConnection type: " + connection.GetType().FullName); 
    } 

    return adapter; 
} 

Answer 4

由於.NET 4.5，編寫提供獨立的代碼時，你現在可以使用DbProviderFactories.GetFactory重載接受DbConnection以獲得正確的供應商工廠，從中可以再創建一個數據適配器。

例子：

DbDataAdapter CreateDataAdapter(DbConnection connection) 
{ 
    return DbProviderFactories.GetFactory(connection).CreateDataAdapter(); 
} 

_{似乎有人在ADO.NET團隊閱讀他的答案伊恩·博伊德評論... :)}

Answer 5

你可以用另一種方式來獲取數據到數據表沒有DbDataAdapter。

這裏是我的代碼

   DataTable dt = new DataTable(); 
       using (IDataReader dr = com.ExecuteReader()) 
       { 
        if (dr.FieldCount > 0) 
        { 
         for (int i = 0; i < dr.FieldCount; i++) 
         { 
          DataColumn dc = new DataColumn(dr.GetName(i), dr.GetFieldType(i)); 
          dt.Columns.Add(dc); 
         } 
         object[] rowobject = new object[dr.FieldCount]; 
         while (dr.Read()) 
         { 
          dr.GetValues(rowobject); 
          dt.LoadDataRow(rowobject, true); 
         } 
        } 
       } 
       return dt; 

Answer 6

private static DbDataAdapter CreateDataAdapter(DbCommand cmd) 
{ 
    DbDataAdapter adapter; 

    /* 
    * DbProviderFactories.GetFactory(DbConnection connection) seams buggy 
    * (.NET Framework too old?) 
    * this is a workaround 
    */ 
    string name_space = cmd.Connection.GetType().Namespace; 
    DbProviderFactory factory = DbProviderFactories.GetFactory(name_space); 
    adapter = factory.CreateDataAdapter(); 
    adapter.SelectCommand = cmd; 
    return adapter; 
}