bool Locked(string key)
{
  if (string.Compare(key, "", StringComparison.InvariantCulture) != 0) return true;
  return key.Length == 0;
}

bool Locked(string key)
{
  if (string.Compare(key, "", StringComparison.InvariantCulture) != 0) return true;
  return key.Trim('\0').Length == 0;
}

key="\u0BE6"

------解决方案--------------------
A similar oddity would be characters with no weight like U+FFFD.  So if I have str = "A\xFFFD\xFFFD\xFFFD", then all of str.Substring(0,1) == str.Substring(0,2) == str.Substring(0,3) == str.Substring(0,4) == "A".  And in this case str.StartsWith("A") would be true.
但是我试验了下:
C# code

string str2 = "A\xFFFD\xFFFD\xFFFD";
            string find2 = "A";

            Console.WriteLine("str2 = " + str2);
            Console.WriteLine("1  -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-");
            Console.WriteLine("Substring: " + (str2.Substring(0, 1) == find2) + "   Substring is:" + str2.Substring(0, 1));
            Console.WriteLine("StartsWith:" + str2.StartsWith(find2));
            Console.WriteLine("IndexOf:   " + str2.IndexOf(find2));

            Console.WriteLine("2  -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-");
            Console.WriteLine("Substring: " + (str2.Substring(0, 2) == find2) + "   Substring is:" + str2.Substring(0, 2));
            Console.WriteLine("StartsWith:" + str2.StartsWith(find2));
            Console.WriteLine("IndexOf:   " + str2.IndexOf(find2));

            Console.WriteLine("3  -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-");
            Console.WriteLine("Substring: " + (str2.Substring(0, 3) == find2) + "   Substring is:" + str2.Substring(0, 3));
            Console.WriteLine("StartsWith:" + str2.StartsWith(find2));
            Console.WriteLine("IndexOf:   " + str2.IndexOf(find2));

            Console.WriteLine("4  -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-");
            Console.WriteLine("Substring: " + (str2.Substring(0, 4) == find2) + "   Substring is:" + str2.Substring(0, 4));
            Console.WriteLine("StartsWith:" + str2.StartsWith(find2));
            Console.WriteLine("IndexOf:   " + str2.IndexOf(find2));

------解决方案--------------------
目前,所有没清楚本贴写的是什么的朋友, 试试下面这段代码, 跟踪一下,就该清楚了.  
如果还不清楚的话, 看看t 的值 !  


C# code

string str1 = "Mu\x0308nchen";
string t = "x\x0308";
string str = "Muchen";
string find = "Mu";
Console.WriteLine("Substring: " + (str.Substring(0, 2) == find) + "   Substring is:" +str.Substring(0, 2));
Console.WriteLine("StartsWith:" + str.StartsWith(find));
Console.WriteLine("IndexOf:   " + str.IndexOf(find));