虽然Asp.Net Core.Identity提供了IdentityUser类，但是在有些情况下我们需要一些额外的用户信息，比如性别，年龄等，这时候就需要来扩展IdentityUser类以达到我们的需求。

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namespace Microsoft.AspNetCore.Identity

{

    //

    // 摘要:

    //     Represents a user in the identity system

    //

    // 类型参数:

    //   TKey:

    //     The type used for the primary key for the user.

    public class IdentityUser<TKey> where TKey : IEquatable<TKey>

    {

        //

        // 摘要:

        //     Initializes a new instance of Microsoft.AspNetCore.Identity.IdentityUser`1.

        public IdentityUser();

        //

        // 摘要:

        //     Initializes a new instance of Microsoft.AspNetCore.Identity.IdentityUser`1.

        //

        // 参数:

        //   userName:

        //     The user name.

        public IdentityUser(string userName);

        //

        // 摘要:

        //     Gets or sets the date and time, in UTC, when any user lockout ends.

        //

        // 言论：

        //     A value in the past means the user is not locked out.

        public virtual DateTimeOffset? LockoutEnd { get; set; }

        //

        // 摘要:

        //     Gets or sets a flag indicating if two factor authentication is enabled for this

        //     user.

        [PersonalData]

        public virtual bool TwoFactorEnabled { get; set; }

        //

        // 摘要:

        //     Gets or sets a flag indicating if a user has confirmed their telephone address.

        [PersonalData]

        public virtual bool PhoneNumberConfirmed { get; set; }

        //

        // 摘要:

        //     Gets or sets a telephone number for the user.

        [ProtectedPersonalData]

        public virtual string PhoneNumber { get; set; }

        //

        // 摘要:

        //     A random value that must change whenever a user is persisted to the store

        public virtual string ConcurrencyStamp { get; set; }

        //

        // 摘要:

        //     A random value that must change whenever a users credentials change (password

        //     changed, login removed)

        public virtual string SecurityStamp { get; set; }

        //

        // 摘要:

        //     Gets or sets a salted and hashed representation of the password for this user.

        public virtual string PasswordHash { get; set; }

        //

        // 摘要:

        //     Gets or sets a flag indicating if a user has confirmed their email address.

        [PersonalData]

        public virtual bool EmailConfirmed { get; set; }

        //

        // 摘要:

        //     Gets or sets the normalized email address for this user.

        public virtual string NormalizedEmail { get; set; }

        //

        // 摘要:

        //     Gets or sets the email address for this user.

        [ProtectedPersonalData]

        public virtual string Email { get; set; }

        //

        // 摘要:

        //     Gets or sets the normalized user name for this user.

        public virtual string NormalizedUserName { get; set; }

        //

        // 摘要:

        //     Gets or sets the user name for this user.

        [ProtectedPersonalData]

        public virtual string UserName { get; set; }

        //

        // 摘要:

        //     Gets or sets the primary key for this user.

        [PersonalData]

        public virtual TKey Id { get; set; }

        //

        // 摘要:

        //     Gets or sets a flag indicating if the user could be locked out.

        public virtual bool LockoutEnabled { get; set; }

        //

        // 摘要:

        //     Gets or sets the number of failed login attempts for the current user.

        public virtual int AccessFailedCount { get; set; }

        //

        // 摘要:

        //     Returns the username for this user.

        public override string ToString();

    }

}

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　　接下来我们就来定义一个继承自IdentityUser类的ApplicationUser类。

public class ApplicationUser : IdentityUser

{

    public string City { get; set; }

}

　　然后在AppDbContext中继承泛型 IdentityDbContext<ApplicationUser>类。并且在Startup中注入的时候把IdentityUser修改为ApplicationUser后，再做数据库迁移，如果之前已经迁移过，则需要替换项目中所有的IdentityUser为ApplicationUser。

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public class AppDbContext:IdentityDbContext<ApplicationUser>

{

    public AppDbContext(DbContextOptions<AppDbContext> options):base(options)

    {

    }

    public DbSet<Student> Students { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)

    {

        base.OnModelCreating(modelBuilder);

        modelBuilder.Seed();

    }

}

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services.AddIdentity<ApplicationUser, IdentityRole>()

    .AddErrorDescriber<CustomIdentityErrorDescriber>()

    .AddEntityFrameworkStores<AppDbContext>();