如何根据提供者名称构建DbConnection？
示例提供商名称
> System.Data.sqlClient
> 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"/>
你可以看到他们都使用不同的提供者.当我来创建一个连接的时候,我必须知道要创建什么样的DbConnection,例如：
> sqlConnection
> OleDbConnection
> OdbcConnection
> FbConnection
connectionStrings条目包含一个providerName,但这些不是DbConnection后代类的名称,而是一个命名空间
我如何根据字符串providerName构建一个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();
}
解决方法
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;
}
