This is because the file which has triggered the created event is likley still being copied to the target destination. Your code is trying to touch the file too quickly. I recommend putting a delay before accessing the file. I have a function which waits until the file becomes available, with a timeout of course:

private Boolean FileTransferComplete(string fullPath)
{
while (true)
{
try
{
using (StreamReader stream = new StreamReader(fullPath))
{
return true;
}
}
catch (Exception ex)
{
// If this file no longer exists then ignore it
if (ex.Message.Contains("Could not find file"))
{
return false;
}
Console.WriteLine("File is busy... Waiting for file to become available.");
Thread.Sleep(2000);
}
}
}