ASP.NET:如何从web.config ConnectionString创建连接？

Question

如何根据提供者名称构建DbConnection ？

样本提供者的名称小号

• System.Data.SqlClient的
• System.Data.OleDb
• System.Data.Odbc
• FirebirdSql.Data.FirebirdClient

我有连接字符串存储在我的IIS服务器的web.config文件中:

<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"/>

您可以看到他们都使用不同的提供商.当我需要创建连接时,我必须知道要创建什么样的DbConnection,例如:

• 的SqlConnection
• 的OleDbConnection
• OdbcConnection
• FbConnection

connectionStrings条目包含providerName,但这些不是DbConnection后代类的名称,但似乎是名称空间

如何根据字符串providerName转换构造DbConnection ？

---

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();

}

Answer 1

如果你走这条路线,我想你会想要使用DbProviderFactories类来获得可用于构建连接的DbProviderFactory.我没有尝试过这个代码,但我认为它会起作用.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;
}