RegEx pattern produces ParserError

I've tried this example and had the same parser error reported here:
https://forums.asp.net/t/2088064.aspx?Membership+Password+Strength+Regular+Expression+Property

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#### Document Details

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* ID: cd696e21-30aa-99b8-a7db-f54a6a532f17
* Version Independent ID: 2e9db142-4fbb-4c09-a7a5-be5b068e2073
* Content: [Membership.PasswordStrengthRegularExpression Property (System.Web.Security)](https://docs.microsoft.com/en-us/dotnet/api/system.web.security.membership.passwordstrengthregularexpression?redirectedfrom=MSDN&view=netframework-4.7.2#System_Web_Security_Membership_PasswordStrengthRegularExpression)
* Content Source: [xml/System.Web.Security/Membership.xml](https://github.com/dotnet/dotnet-api-docs/blob/master/xml/System.Web.Security/Membership.xml)
* Product: **dotnet-api**
* GitHub Login: @dotnet-bot
* Microsoft Alias: **dotnetcontent**