Random password Creator C# code

public static string CreateRandomPassword(int PasswordLength)
{
string _allowedChars = "abcdefghijkmnopqrstuvwxyzABCDEFGH­JKLMNOPQRSTUVWXYZ0123456789!@$?";
Random randNum = new Random();
char[] chars = new char[PasswordLength];
int allowedCharCount = _allowedChars.Length;
for (int i = 0; i < PasswordLength; i++)
{
chars[i] = _allowedChars[(int)((_allowedChars.Length) * randNum.NextDouble())];
}
return new string(chars);
}