Cannot convert null literal to non-nullable reference type.

Cannot convert null literal to non-nullable reference type.

Cannot convert null literal to non-nullable reference type.

Cannot convert null literal to non-nullable reference type.

'DataContext.Users' hides inherited member 'IdentityUserContext<IdentityUser, string, IdentityUserClaim<string>, IdentityUserLogin<string>, IdentityUserToken<string>>.Users'. To make the current member override that implementation, add the override keyword. Otherwise add the new keyword.

Non-nullable property 'UserManager' must contain a non-null value when exiting constructor. Consider declaring the property as nullable.

Possible null reference argument for parameter 'user' in 'Task<IList<string>> UserManager<IdentityUser>.GetRolesAsync(IdentityUser user)'.

Possible null reference argument for parameter 'user' in 'Task<IList<string>> UserManager<IdentityUser>.GetRolesAsync(IdentityUser user)'.

Converting null literal or possible null value to non-nullable type.