password validation in C#

public bool IsValidPassword(string password)
{
 string MatchNumberPattern = "^.*(?=.{8,})(?=.*\\d)(?=.*[a-z])(?=.*[A-Z])(?=.*[@#$%^&+=]).*$";
 if (!string.IsNullOrEmpty(TextBox2.Text.Trim)) {
  if (!Regex.IsMatch(password), MatchNumberPattern)) {
   return false;
  }
 }
}

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Must be at least 8 characters
-Must contain at least one lower case,oneupper case,
-One digit and one special character