Code for Generating Random Challan No in C#.net

------------function--------------------------------------------
private int RandomInt(int min, int max)
{
Random random = new Random();
return random.Next(min, max);
}

private string RandomString(int size, bool lowerCase)
{
StringBuilder builder = new StringBuilder();
Random random = new Random();
char ch;
int i;
for (i = 0; i <= size - 1; i++)
{
ch = Convert.ToChar(Convert.ToInt32((26 * random.NextDouble() + 65)));
builder.Append(ch);
}
//i If lowerCase Then
// Return builder.ToString().ToLower()
//End If
return builder.ToString();
}
//RandomString

public string GetRandChlnNo()
{
StringBuilder builder = new StringBuilder();
builder.Append(RandomString(2, true));
builder.Append(RandomInt(1000, 9999));
builder.Append(RandomString(2, false));
return builder.ToString();
}