Question

i know this code dont work but is describes good what im trying to do, i want to run the code inside the if check when Lastwritetime is greater then oldvalue date.

private void timer1_Tick(object sender, EventArgs e)
{
    DateTime lastWriteTime = File.GetLastWriteTime(@"C:\temp\test_folder\TestFile.txt");

    if (lastWriteTime.ToString() > oldValue.ToString())
    {
        MessageBox.Show("Succsess");
    }
    string oldValue = lastWriteTime.ToString();
}

edit:
im not using SystemfileWatcher because of the mulitple events raised on change.

Answer 1

Why are you comparing string representations? If oldValue is DateTime as well, just compare them as is:

if(lastWriteTime.ToString() > oldValue)
    // ...

Plus, make sure that the scope of oldValue is greater than the scope of timer1_Tick (that is, ensure that it’s a class member variable).

And of course, do not reinvent the wheel: FileSystemWatcher.