Here's a tip for Disabling Users with Simple Membership (Microsoft ASP.NET). The Database for Simple Membership includes an "IsConfirmed". This wasn't really intended for use with disabling/locking a User but can sort of work. A better idea would be to have a Role for "Active" Users.

Activate-Deactivate-SimpleMembership-Users.md

How to lock/unlock a user in MVC SimpleMembership

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I find it easiest to use Roles to do this. Have a ActiveUser role and tag your controllers or actions with a Authorize attribute.

[Authorize(Roles = "ActiveUser")]

Then some simple admin to add or remove users from the role to unlock and lock their access to everything protected with that roles attribute.

Roles.AddUserToRole(user.Username, "ActiveUser");

Roles.RemoveUserFromRole(user.Username, "ActiveUser");