ASP.NET自带用户注册时密码强度需要数字+字母+符号，如何自定义强度？比如降低强度，只需数字+密码。
有个ajax控件的,passwordstrenth.
C# code:
请输入密码：<asp:TextBox ID="TextBox2" runat="server" TextMode="Password"></asp:TextBox>
<ajaxToolkit:PasswordStrength ID="TextBox2_PasswordStrength" runat="server" Enabled="True"
HelpStatusLabelID="Label2" MinimumNumericCharacters="1" MinimumSymbolCharacters="1"
PreferredPasswordLength="15" PrefixText="强度：" StrengthIndicatorType="BarIndicator"
StrengthStyles="BarIndicator_TextBox2_weak;BarIndicator_TextBox2_average;BarIndicator_TextBox2_good"
TargetControlID="TextBox2" TextCssClass="" TextStrengthDescriptions="非常弱;弱;一般;强;极佳"
BarBorderCssClass="BarBorde
