I am usign Membership.ValidateUser(model.UserName, model.Password)) in a app web .net Framework 4.7.1 c# to validate domain users. I only check that the user and password is correct, nothing else.

I have the next config in my web.config:

  <authentication mode="Forms">
      <forms name=".ADAuthCookie" loginUrl="~/Account/Login" timeout="450" slidingExpiration="true" protection="All"/>
    </authentication>
    <sessionState timeout="300"/>
    <authorization>
      <deny users="?"/>
      <allow users="*"/>
    </authorization>
    <membership defaultProvider="ADMembershipProvider" userIsOnlineTimeWindow="1">
      <providers>
        <clear/>
        <add name="ADMembershipProvider" type="System.Web.Security.ActiveDirectoryMembershipProvider" connectionStringName="ADConnectionString" attributeMapUsername="sAMAccountName"/>
      </providers>
    </membership>

All works fine, but each 2 or 3 months the Membership.ValidateUser suddenly doesn’t work, I think that we are not freeign the users and is necessary restart the application pool to liberate it after a lot of connections and get the maximun of it (I don’t know).

I need help, thanks a lot.