数据源连接字符串格式是固定的，需要以DSN=i-model datasource开头。示例代码如下：

                    string connectionString = "DSN=i-model datasource;imodel=" + fileName; // C:\\SimbaEngineSDK_8.0.2.3_bently_preview\\SimbaEngineSDK_8.0.2.3_bently_preview\\Databases\\Text\\PM-Week 16.i.dgn;";
                    connection = new OdbcConnection (connectionString);
                    connection.Open ();