C#

string path = @"C:\";
string[] subDirs = System.IO.Directory.GetDirectories(path);
int count = 0;
for (int i = 0; i < subDirs.Length; i++)
	count += System.IO.Directory.GetFiles(subDirs[i]).Length;
// Do sth with 'count'.

// subDI var. is not used
// System.IO.DirectoryInfo subDI = new System.IO.DirectoryInfo(path);
// Testing list:
List<string> result = new List<string>();
foreach (String sub in Directory.GetDirectories(path)) {
	// 1. Do not call GetFiles function twice if don't have to!
	// This loop was useless while you never use file variable!
	// foreach (String file in Directory.GetFiles(sub, "*.dat")) {
	// If you declare count inside a loop, it will be initialized down to zero
	// each time. Was it intended?
	int count = 0;
	foreach (string subSub in Directory.GetDirectories(sub))
		count += Directory.GetFiles(subSub).Length;
	// Do not use Substring here!
	// String subName = sub.Substring(sub.LastIndexOf(@"\") + 1);
	string subName = Path.GetFileName(sub);
	// sub is a string, not a string array, so sub[i] will give a i'th CHAR of a string.
	// for (int i = 0; i < sub.Length; i++)
	// this.toolStripProgressBar1.Value += 50;
	// Create ListView item etc.

	// Use some simple code for testing!
	result.Add(subName + ": " + count.ToString() + " files in subdirectories");
}

void A()
{
  string str = new string();
  str = "text";
  // At the end of the method str dies.
}

void B()
{
  string str = new string();  // allocates a new variable regardles the name is the same.
  Console.WriteLine(str); // str is equal to "" here.
}

Timer oT = new Timer();
private void button1_Click(object sender, EventArgs e)
{
string[] lines1 = System.IO.File.ReadAllLines("inställningar.txt");
string path1 = lines1[8];
string tid = lines1[0];
int dimension = Convert.ToInt32(tid);
//Timer oT = new Timer();
oT.Interval = dimension;
oT.Start();
}

private void button2_Click(object sender, EventArgs e)
{
//Timer oT = new Timer();
// Did you mean "-="?
//oT.Tick += new System.EventHandler(Timerfunction);
oT.Tick -= TimerFunction;
oT.Stop();
}

namespace X
{
//file1.cs
class A
{
}
class B : A
{
}
class C
{
   A someMember;
}
}

//file1.cs
namespace X
{
class A
{
}
}
//file2.cs
namespace X
{
class B : A  // ERROR
{
}
class C
{
   A someMember; // ERROR
}
}

//file1.cs:

using X.Y;   //ERROR
namespace X
{
}

//file2.cs
namespace X.Y
{
}