IdentityUser.cs

static void Main(string[] args)
{
   MapperConfiguration config = new MapperConfiguration(c =>
   {
		c.CreateMap<UserViewModel, ApplicationUsers>().ConvertUsing<UserConvertor>();
   });
   var mapper = config.CreateMapper();
	var user = new UserViewModel
	{
		Email = "[email protected]",
		MobileNumber = "test",
		Password = "test",
		ReTypePassword = "test",
		Username = "test",	
	};
	mapper.ConfigurationProvider.AssertConfigurationIsValid();
	var result= mapper.Map<ApplicationUsers>(user).Dump();
}

public class UserConvertor : ITypeConverter<UserViewModel, ApplicationUsers>
{

   public ApplicationUsers Convert(UserViewModel source, ApplicationUsers destination, ResolutionContext context)
   {
       if (context==null||source == null) return null;
       
       return new ApplicationUsers
       {
           UserName = source.Username,
           Email = source.Email,
           PhoneNumber = source.MobileNumber
       };
   }
}

public class UserViewModel
{
   public string MobileNumber { get; set; }
   public string Email { get; set; }
   public string Username { get; set; }
   public string Password { get; set; }
   public string ReTypePassword { get; set; }
}

public class IdentityUser<TKey> where TKey : IEquatable<TKey>
{
   public IdentityUser() {
   	Roles = new List<IdentityUser<TKey>>();
   }

   public IdentityUser(string userName) : this()
   {
       UserName = userName;
   }

   public virtual TKey Id { get; set; }
   public virtual string UserName { get; set; }
   public virtual string NormalizedUserName { get; set; }

   /// <summary>
   ///     Email
   /// </summary>
   public virtual string Email { get; set; }

   public virtual string NormalizedEmail { get; set; }

   /// <summary>
   ///     True if the email is confirmed, default is false
   /// </summary>
   public virtual bool EmailConfirmed { get; set; }

   /// <summary>
   ///     The salted/hashed form of the user password
   /// </summary>
   public virtual string PasswordHash { get; set; }

   /// <summary>
   /// A random value that should change whenever a users credentials change (password changed, login removed)
   /// </summary>
   public virtual string SecurityStamp { get; set; }

   /// <summary>
   /// A random value that should change whenever a user is persisted to the store
   /// </summary>
   public virtual string ConcurrencyStamp { get; set; }

   /// <summary>
   ///     PhoneNumber for the user
   /// </summary>
   public virtual string PhoneNumber { get; set; }

   /// <summary>
   ///     True if the phone number is confirmed, default is false
   /// </summary>
   public virtual bool PhoneNumberConfirmed { get; set; }

   /// <summary>
   ///     Is two factor enabled for the user
   /// </summary>
   public virtual bool TwoFactorEnabled { get; set; }

   /// <summary>
   ///     DateTime in UTC when lockout ends, any time in the past is considered not locked out.
   /// </summary>
   public virtual DateTimeOffset? LockoutEnd { get; set; }

   /// <summary>
   ///     Is lockout enabled for this user
   /// </summary>
   public virtual bool LockoutEnabled { get; set; }

   /// <summary>
   ///     Used to record failures for the purposes of lockout
   /// </summary>
   public virtual int AccessFailedCount { get; set; }

   /// <summary>
   ///     Navigation property for users in the role
   /// </summary>
   public virtual ICollection<IdentityUser<TKey>> Roles { get; set; }

   /// <summary>
   /// Returns a friendly name
   /// </summary>
   /// <returns></returns>
   public override string ToString()
   {
       return UserName;
   }
}

public class ApplicationUsers : IdentityUser<Guid>
{
}