If you are going to reuse an object several times, 
consider using the instance method of DirectoryInfo instead of the corresponding static methods of the Directory class, 
because a security check will not always be necessary.

Code1:
// The following example displays the names and sizes
// of the files in the specified directory.
using System;
using System.IO;

public class FileLength
{
    public static void Main()
    {
        // Make a reference to a directory.
        DirectoryInfo di = new DirectoryInfo("c:\\");
        // Get a reference to each file in that directory.
        FileInfo[] fiArr = di.GetFiles();
        // Display the names and sizes of the files.
        Console.WriteLine("The directory {0} contains the following files:", di.Name);
        foreach (FileInfo f in fiArr)
            Console.WriteLine("The size of {0} is {1} bytes.", f.Name, f.Length);
    }
}
//This code produces output similar to the following; 
//results may vary based on the computer/file structure/etc.:
//
//The directory c:\ contains the following files:
//The size of MyComputer.log is 274 bytes.
//The size of AUTOEXEC.BAT is 0 bytes.
//The size of boot.ini is 211 bytes.
//The size of CONFIG.SYS is 0 bytes.
//The size of hiberfil.sys is 1072775168 bytes.
//The size of IO.SYS is 0 bytes.
//The size of MASK.txt is 2700 bytes.
//The size of mfc80.dll is 1093632 bytes.
//The size of mfc80u.dll is 1079808 bytes.
//The size of MSDOS.SYS is 0 bytes.
//The size of NTDETECT.COM is 47564 bytes.
//The size of ntldr is 250032 bytes.
//The size of pagefile.sys is 1610612736 bytes.
//The size of UpdatePatch.log is 22778 bytes.
//The size of UpdatePatch.txt is 30 bytes.
//The size of wt3d.ini is 234 bytes.

Code2: 
using System;
using System.IO;

class Test 
{
    public static void Main() 
    {
        // Specify the directories you want to manipulate.
        DirectoryInfo di = new DirectoryInfo(@"c:\MyDir");
        try 
        {
            // Determine whether the directory exists.
            if (di.Exists) 
            {
                // Indicate that the directory already exists.
                Console.WriteLine("That path exists already.");
                return;
            }

            // Try to create the directory.
            di.Create();
            Console.WriteLine("The directory was created successfully.");

            // Delete the directory.
            di.Delete();
            Console.WriteLine("The directory was deleted successfully.");

        } 
        catch (Exception e) 
        {
            Console.WriteLine("The process failed: {0}", e.ToString());
        } 
        finally {}
    }
}

Code3: To copy a directory and its contents.
using System;
using System.IO;

class CopyDir
{
    public static void Copy(string sourceDirectory, string targetDirectory)
    {
        DirectoryInfo diSource = new DirectoryInfo(sourceDirectory);
        DirectoryInfo diTarget = new DirectoryInfo(targetDirectory);

        CopyAll(diSource, diTarget);
    }

    public static void CopyAll(DirectoryInfo source, DirectoryInfo target)
    {
        // Check if the target directory exists, if not, create it.
        if (Directory.Exists(target.FullName) == false)
        {
            Directory.CreateDirectory(target.FullName);
        }

        // Copy each file into it's new directory.
        foreach (FileInfo fi in source.GetFiles())
        {
            Console.WriteLine(@"Copying {0}\{1}", target.FullName, fi.Name);
            fi.CopyTo(Path.Combine(target.ToString(), fi.Name), true);
        }

        // Copy each subdirectory using recursion.
        foreach (DirectoryInfo diSourceSubDir in source.GetDirectories())
        {
            DirectoryInfo nextTargetSubDir =
                target.CreateSubdirectory(diSourceSubDir.Name);
            CopyAll(diSourceSubDir, nextTargetSubDir);
        }
    }

    public static void Main()
    {
        string sourceDirectory = @"c:\sourceDirectory";
        string targetDirectory = @"c:\targetDirectory";

        Copy(sourceDirectory, targetDirectory);
    }

    // Output will vary based on the contents of the source directory.
}