public void RemoveDuplicates()
{
var fis = new List <FileInfo>
{
new FileInfo("z:\\a.txt"),
new FileInfo("z:\\a.txt"),
new FileInfo("z:\\a.txt"),
new FileInfo("z:\\a.txt")
};
var fisD = File.Distinct(fis);
Assert.AreEqual(1, fisD.Count);
Assert.IsTrue(fisD.Any(f => f.FullName == "z:\\a.txt"));
// nothing has changed
Assert.AreEqual(4, fis.Count(f => f.FullName == "z:\\a.txt"));
}