C# Retrieving correct DbConnection object by conne

问题:

I have a connection string being passed to a function, and I need to create a DbConnection based object (i.e. SQLConnection, OracleConnection, OLEDbConnection etc) based on this string.

Is there any inbuilt functionality to do this, or any 3rd party libraries to assist. We are not necessarily building this connection string, so we cannot rely on a format the string is written in to determine its type, and I would prefer not to have to code up all combinations and permutations of possible connection strings

回答1:

   DbConnection GetConnection(string connStr)
    { string providerName = null;
      var    csb = new DbConnectionStringBuilder{ConnectionString=connStr};

      if (csb.ContainsKey("provider")) 
       { providerName = csb["provider"].ToString();
       }          
      else
       { var css = ConfigurationManager
                           .ConnectionStrings
                           .Cast<ConnectionStringSettings>()
                           .FirstOrDefault(x=>x.ConnectionString==connStr);
         if (css != null) providerName = css.ProviderName;
       }

      if (providerName != null) 
       { var providerExists =  DbProviderFactories
                                     .GetFactoryClasses()
                                     .Rows.Cast<DataRow>()
                                     .Any(r=>r[2].Equals(providerName));
         if (providerExists) 
          { var factory = DbProviderFactories.GetFactory(providerName);
            var dbConnection = factory.CreateConnection();

            dbConnection.ConnectionString = connStr;
            return dbConnection;
          }
       }

      return null;
   }

回答2:

if you're using framework 2.0 or above, and you can get them to pass in a second string with the driver class, you can use the dbProviderFactory class to load the driver for you.

DbProviderFactory dbProviderFactory = DbProviderFactories.GetFactory(myDriverClass);
DbConnection dbConnection = dbProviderFactory.CreateConnection();
dbConnection.ConnectionString = myConnectionString;

Here's an MSDN link to the Factory class: http://msdn.microsoft.com/en-us/library/wda6c36e.aspx

回答3:

You should be able to parse out the Provider section and pass it into DbProviderFactories.GetFactory which will return a OdbcFactory, OleDbFactory or SqlClientFactory and let you then perform CreateConnection etc.

I'm not sure how this would work with Oracle unless they provide an OracleDbFactory.

回答4:

Most connection strings (at least in .NET 2.0) also have a providerName property that goes with them. So a SQL connection string will have a provider Name like:

providerName="System.Data.SqlClient"

So your method would need to accept both the connection string and the provider name and then you could use the DbProviderFactory as mentioned by damieng.