WPF中的密码框

<PasswordBox Name="PasswordBox" Margin="5" Padding="5" PreviewKeyDown="Txtpassword_PreviewKeyUp"/>

IntPtr p = System.Runtime.InteropServices.Marshal.SecureStringToBSTR(this.PasswordBox.SecurePassword);
            string password = System.Runtime.InteropServices.Marshal.PtrToStringBSTR(p);