查找指定文件夹下最后修改的文件

public partial class mainForm : Form
{
DateTime dt;
String SearchFileResult = "";
public mainForm()
{
InitializeComponent();
}

private void Form1_Load(object sender, EventArgs e)
{
dt = DateTime.Now;

}

private void menuItem6_Click(object sender, EventArgs e)
{
String s = SearchFile("//My Documents");
if (s == String.Empty)
MessageBox.Show("您没有被修改的文档");
else
MessageBox.Show("最后修改的文件是" + s);

}

private String SearchFile(String theDirectory)
{
String[] file = Directory.GetFiles(theDirectory);
foreach (String f in file)
{
String temp = Path.Combine(theDirectory, f);
DateTime tempdt = File.GetLastWriteTime(temp);

if (tempdt.CompareTo(dt) > 0)
{
dt = new DateTime(tempdt.Year, tempdt.Month, tempdt.Day, tempdt.Hour, tempdt.Minute, tempdt.Second);
SearchFileResult = Path.Combine(theDirectory, f);
}
}
//递归查找目录树
String[] directories = Directory.GetDirectories(theDirectory);
foreach (String d in directories)
{
SearchFileResult = SearchFile(d);
}
return SearchFileResult;
}