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

如何构建基于 DbConnection提供商名称?

Sample 提供商名称s

• 系统.数据.SqlClient
• 系统.数据.OleDb
• 系统数据.ODBC
• FirebirdSql.Data.FirebirdClient

我的 IIS 服务器的 web.config 文件中存储有连接字符串：

<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。当我创建连接时，我必须知道要创建哪种 DbConnection，例如：

• sql连接
• OleDb连接
• Odbc连接
• Fb连接

连接字符串条目包含一个提供商名称，但这些不是 DbConnection 后代类的名称，但似乎是名称空间

我如何根据字符串构造 DbConnection提供商名称?

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();

}

如果您选择这条路线，我想您会想要使用 DbProviderFactories 类来获取可用于构造连接的 DbProviderFactory。我还没有尝试过这段代码，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;
}