C#

PermissionSet ps = new PermissionSet(PermissionState.None);
     ps.AddPermission(new SecurityPermission(SecurityPermissionFlag.Execution));
     FileIOPermission fP = new FileIOPermission(PermissionState.None);
     fP.AllFiles = FileIOPermissionAccess.NoAccess;
     fP.AddPathList(FileIOPermissionAccess.PathDiscovery | FileIOPermissionAccess.Read, Environment.CurrentDirectory);


     ps.AddPermission(fP);



         AppDomainSetup ads = new AppDomainSetup();
         ads.ApplicationBase = AppDomain.CurrentDomain.SetupInformation.ApplicationBase;
         AppDomain domain = AppDomain.CreateDomain("Plugins", AppDomain.CurrentDomain.Evidence, ads, ps, CreateStrongName(System.Reflection.Assembly.GetExecutingAssembly()));
         IPlugin finder = (IPlugin)domain.CreateInstanceFromAndUnwrap("MyPluginTest.dll", "MyPluginTest.IPluginTest");
         finder.PerformAction(null);

private void openExcel()
{
            string connectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=""C:\MyLocation\myFile.xls"";Extended Properties=""Excel 12.0;HDR=NO;""";
            OleDbConnection excelConnection = new OleDbConnection(connectionString);
            excelConnection.Open();

            string strSQL = "SELECT * FROM [Sheet1$]";

            OleDbCommand dbCommand = new OleDbCommand(strSQL, excelConnection);
            OleDbDataAdapter dataAdapter = new OleDbDataAdapter(dbCommand);

            // create data table
            DataTable dTable = new DataTable();
            dataAdapter.Fill(dTable);

            aListBoxControl.DataSource = dTable;

            // dispose used objects
            dTable.Dispose();
            dataAdapter.Dispose();
            dbCommand.Dispose();

            excelConnection.Close();
            excelConnection.Dispose();
        }

[DllImport("BTDataAccess.dll")]
        static extern uint BTReadBu( [In, MarshalAs(UnmanagedType.BStr)] string filePath);