System.Data.Common.DbProviderFactories

首先, 取得连接串:
ConnectionStringSettings myConnectionSettings = ConfigurationManager.ConnectionStrings[myName];
其中, myName 在App.config中配置, 如:
<configuration>
 <connectionStrings>
  <add name="SQL Server" providerName="System.Data.SqlClient"
    connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Databases\MyData.mdf;Integrated Security=True;User Instance=True" />
</connectionStrings>
</configuration>
得到Provider
DbProviderFactory myProvider = DbProviderFactories.GetFactory(myConnectionSettings.ProviderName);
得到Connection
DbConnection myConnection = myProvider.CreateConnection();
myConnection.ConnectionString = myConnectionSettings.ConnectionString;
myConnection.Open();

    DbDataAdapter myAdapter = myProvider.CreateDataAdapter();
    DbCommand myCommand = myProvider.CreateCommand();
    
    // Create the DataSet so that we can populate the datagrid
    string myQuery = "SELECT * FROM SampleData";
    DataSet myDataSet = new DataSet();

    myCommand.Connection = myConnection;
    myCommand.CommandText = myQuery;

    myAdapter.SelectCommand = myCommand;

    myAdapter.Fill(myDataSet);
    
    displayDataGridView.DataSource = myDataSet.Tables[0];

这是Vs Sample中例子DBFactory中采用的方式.