HttpContext.GetOwinContext().GetUserManager() return null

Question

I\'ve used ASP.NET Identity 2 for creating role but the result of HttpContext.GetOwinContext().GetUserManager() was null.

Then I could

Answer 1

Most likely you have missed giving OwinContext the way to create ApplicationUserManager.
For that you'll need to have these in your public void Configuration(IAppBuilder app)

app.CreatePerOwinContext(ApplicationUserManager.Create);
app.CreatePerOwinContext(AppRoleManager.Create);

This will register delegates that create UserManager and RoleManager with OwinContext and only after that you can call these back in your controllers.