ado.net – ASP.NET：如何从web.config ConnectionString创建一个连接？

<connectionStrings>
  <add name="development"
        connectionString="Provider = IBMDA400; Data source = MY_SYSTEM_NAME; User Id = myUsername; password = mypassword;" 
        providerName="System.Data.oleDb" />
  <add name="live" 
        connectionString="usd=sa;pwd=password;server=deathstar;" 
        providerName="System.Data.odbc" />
  <add name="tesTing" 
        connectionString="usd=sa;pwd=password;server=deathstar;" 
        providerName="System.Data.SqlClient" />
  <add name="offline"
        connectionString="Server=localhost;User=SYSDBA;password=masterkey;Charser=NONE;Database=c:\data\mydb.fdb"
        providerName="FirebirdSql.Data.FirebirdClient"/>

public DbConnection GetConnection(String connectionName)
{
    //Get the connectionString infomation
    ConnectionStringSetTings cs = 
          ConfigurationManager.ConnectionStrings[connectionName];
    if (cs == null)
       throw new ConfigurationException("Invalid connection name \""+connectionName+"\");

    //Create a connection based on the provider
    DbConnection conn = new DbConnection();

}

解决方法@H_618_28@

如果你走这条路线,我想你会想要使用DbProviderFactories类获得一个可以用来构建连接的DbProviderFactory.我没有尝试过这个代码,但我认为它会奏效.您可能需要使用DbProviderFactories类上的GetFactoryClasses方法查找提供程序名称,并使用InvariantName.

public DbConnection GetConnection(String connectionName)
{
   //Get the connection String info from web.config
   ConnectionStringSetTings cs= 
         ConfigurationManager.ConnectionStrings[connectionName];

   //documented to return null if it couldn't be found
   if (cs == null)
      throw new ConfigurationErrorsException("Invalid connection name \""+connectionName+"\"");

   //Get the factory for the given provider (e.g. "System.Data.SqlClient")
   DbProviderFactory factory = 
         DbProviderFactories.GetFactory(cs.ProviderName);

   //Undefined behaviour if GetFactory couldn't find a provider.
   //Defensive test for null factory anyway
   if (factory == null)
      throw new Exception("Could not obtain factory for provider \""+cs.ProviderName+"\"");

   //Have the factory give us the right connection object      
   DbConnection conn = factory.CreateConnection();

   //Undefined behaviour if CreateConnection failed
   //Defensive test for null connection anyway
   if (conn == null)
      throw new Exception("Could not obtain connection from factory");

   //Knowing the connection String,open the connection
   conn.ConnectionString = cs.ConnectionString;
   conn.open()

   return conn;
}