表名的问题在于 OnModelCreating 的覆盖。我对 .Entity<...>().HasKey 的调用正在调用这些表名。有关覆盖的更多信息，请参阅 Olav Nyb0 在此处的回答：Asp.net Identity Validation Error。我已将 OnModelCreating 更新为：
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
}
我的 ApplicationUser 和迁移脚本以 Identity 1.0 为模型，我需要为 Identity 2.0 更新它们。
应用用户：
public class ApplicationUser : IdentityUser
{
public int AcId { get; set; }
public int LcId { get; set; }
}
这是我最终针对我的 SimpleMembership 数据库运行的迁移脚本。有点偏离原始问题，但我将其包含在此处，希望能节省其他人我花在解决问题上的时间。
/****** Object: Table [dbo].[AspNetRoles] Script Date: 4/29/14 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
IF OBJECT_ID('dbo.AspNetUserRoles', 'U') IS NOT NULL
DROP TABLE [dbo].[AspNetUserRoles]
GO
--IF OBJECT_ID('dbo.AspNetUserLogins', 'U') IS NOT NULL
-- DROP TABLE [dbo].[AspNetUserLogins]
--GO
IF OBJECT_ID('dbo.AspNetUserClaims', 'U') IS NOT NULL
DROP TABLE [dbo].[AspNetUserClaims]
GO
IF OBJECT_ID('dbo.AspNetRoles', 'U') IS NOT NULL
DROP TABLE [dbo].[AspNetRoles]
GO
IF OBJECT_ID('dbo.AspNetUsers', 'U') IS NOT NULL
DROP TABLE [dbo].[AspNetUsers]
GO
CREATE TABLE [dbo].[AspNetUsers] (
[Id] NVARCHAR (128) NOT NULL,
[UserName] NVARCHAR (15) NULL,
[AcId] INT NOT NULL,
[LcId] INT NOT NULL,
[Email] NVARCHAR (256) NULL,
[EmailConfirmed] BIT DEFAULT ((0)) NULL,
[PasswordHash] NVARCHAR (MAX) NULL,
[SecurityStamp] NVARCHAR (MAX) NULL,
[PhoneNumber] NVARCHAR (MAX) NULL,
[PhoneNumberConfirmed] BIT DEFAULT ((0)) NULL,
[TwoFactorEnabled] BIT DEFAULT ((0)) NULL,
[LockoutEndDateUtc] DATETIME NULL,
[Lockoutenabled] BIT DEFAULT ((0)) NULL,
[AccessFailedCount] INT DEFAULT ((0)) NOT NULL,
[Discriminator] NVARCHAR (128) NOT NULL,
[CreateDate] DATETIME NULL,
[ConfirmationToken] NVARCHAR (128) NULL,
[IsConfirmed] BIT DEFAULT ((0)) NULL,
[LastPasswordFailureDate] DATETIME NULL,
[PasswordFailuresSinceLastSuccess] INT DEFAULT ((0)) NULL,
[PasswordChangedDate] DATETIME NULL,
[PasswordVerificationToken] NVARCHAR (128) NULL,
[PasswordVerificationTokenExpirationDate] DATETIME NULL,
CONSTRAINT [PK_dbo.AspNetUsers] PRIMARY KEY CLUSTERED ([Id] ASC)
);
GO
CREATE TABLE [dbo].[AspNetRoles] (
[Id] NVARCHAR (128) NOT NULL,
[Name] NVARCHAR (256) NOT NULL,
CONSTRAINT [PK_dbo.AspNetRoles] PRIMARY KEY CLUSTERED ([Id] ASC)
);
GO
CREATE TABLE [dbo].[AspNetUserRoles] (
[UserId] NVARCHAR (128) NOT NULL,
[RoleId] NVARCHAR (128) NOT NULL,
CONSTRAINT [PK_dbo.AspNetUserRoles] PRIMARY KEY CLUSTERED ([UserId] ASC, [RoleId] ASC),
CONSTRAINT [FK_dbo.AspNetUserRoles_dbo.AspNetRoles_RoleId] FOREIGN KEY ([RoleId]) REFERENCES [dbo].[AspNetRoles] ([Id]) ON DELETE CASCADE,
CONSTRAINT [FK_dbo.AspNetUserRoles_dbo.AspNetUsers_UserId] FOREIGN KEY ([UserId]) REFERENCES [dbo].[AspNetUsers] ([Id]) ON DELETE CASCADE
);
GO
CREATE NONCLUSTERED INDEX [IX_RoleId]
ON [dbo].[AspNetUserRoles]([RoleId] ASC);
GO
CREATE NONCLUSTERED INDEX [IX_UserId]
ON [dbo].[AspNetUserRoles]([UserId] ASC);
GO
CREATE TABLE [dbo].[AspNetUserLogins] (
[UserId] NVARCHAR (128) NOT NULL,
[LoginProvider] NVARCHAR (128) NOT NULL,
[ProviderKey] NVARCHAR (128) NOT NULL,
CONSTRAINT [PK_dbo.AspNetUserLogins] PRIMARY KEY CLUSTERED ([UserId] ASC, [LoginProvider] ASC, [ProviderKey] ASC),
CONSTRAINT [FK_dbo.AspNetUserLogins_dbo.AspNetUsers_UserId] FOREIGN KEY ([UserId]) REFERENCES [dbo].[AspNetUsers] ([Id]) ON DELETE CASCADE
);
GO
CREATE NONCLUSTERED INDEX [IX_UserId]
ON [dbo].[AspNetUserLogins]([UserId] ASC);
GO
CREATE TABLE [dbo].[AspNetUserClaims] (
[Id] INT IDENTITY (1, 1) NOT NULL,
[ClaimType] NVARCHAR (MAX) NULL,
[ClaimValue] NVARCHAR (MAX) NULL,
[UserId] NVARCHAR (128) NOT NULL,
CONSTRAINT [PK_dbo.AspNetUserClaims] PRIMARY KEY CLUSTERED ([Id] ASC),
CONSTRAINT [FK_dbo.AspNetUserClaims_dbo.AspNetUsers_User_Id] FOREIGN KEY ([UserId]) REFERENCES [dbo].[AspNetUsers] ([Id]) ON DELETE CASCADE
);
GO
CREATE NONCLUSTERED INDEX [IX_User_Id]
ON [dbo].[AspNetUserClaims]([UserId] ASC);
GO
INSERT INTO AspNetUsers(Id, UserName, BaId, OfcId, PasswordHash, SecurityStamp, Discriminator,
CreateDate, ConfirmationToken, IsConfirmed, LastPasswordFailureDate, PasswordFailuresSinceLastSuccess,
PasswordChangedDate, PasswordVerificationToken, PasswordVerificationTokenExpirationDate)
SELECT UserProfile.UserId, UserProfile.UserName, UserProfile.BaId, UserProfile.OfcId,
webpages_Membership.Password, webpages_Membership.PasswordSalt, 'User', CreateDate,
ConfirmationToken, IsConfirmed, LastPasswordFailureDate, PasswordFailuresSinceLastSuccess,
PasswordChangedDate, PasswordVerificationToken, PasswordVerificationTokenExpirationDate
FROM UserProfile
LEFT OUTER JOIN webpages_Membership ON UserProfile.UserId = webpages_Membership.UserId
GO
INSERT INTO AspNetRoles(Id, Name)
SELECT RoleId, RoleName
FROM webpages_Roles
GO
INSERT INTO AspNetUserRoles(UserId, RoleId)
SELECT UserId, RoleId
FROM webpages_UsersInRoles
GO
IF OBJECT_ID('dbo.webpages_OAuthMembership', 'U') IS NOT NULL
DROP TABLE [dbo].[webpages_OAuthMembership]
GO
IF OBJECT_ID('dbo.webpages_UsersInRoles', 'U') IS NOT NULL
DROP TABLE [dbo].[webpages_UsersInRoles]
GO
IF OBJECT_ID('dbo.webpages_Roles', 'U') IS NOT NULL
DROP TABLE [dbo].[webpages_Roles]
GO
IF OBJECT_ID('dbo.UserProfile', 'U') IS NOT NULL
DROP TABLE [dbo].[UserProfile]
GO
IF OBJECT_ID('dbo.webpages_Membership', 'U') IS NOT NULL
DROP TABLE [dbo].[webpages_Membership]
GO
--INSERT INTO AspNetUserLogins(UserId, LoginProvider, ProviderKey)
--SELECT UserId, Provider, ProviderUserId
--FROM webpages_OAuthMembership
--GO
我没有使用社交登录，因此将 Insert into AspNetUserLogins 注释掉（您确实需要创建表，因为 Identity 2.0 需要它）。
Identity 2.0 AspNetUsers 表默认具有以下字段：
[Id]
[Email]
[EmailConfirmed]
[PasswordHash]
[SecurityStamp]
[PhoneNumber]
[PhoneNumberConfirmed]
[TwoFactorEnabled]
[LockoutEndDateUtc]
[LockoutEnabled]
[AccessFailedCount]
[UserName]
我仍在试验中，请根据您的最佳判断来确定需要从 pages_Membership 表迁移的内容。此时我可以登录。
更新：
在我的 ApplicationUser 中，我重写了 UserName 以缩短该字段。不要这样做，它会导致身份验证错误。您可以控制迁移脚本中的字段长度。我已经删除了 OP 中的覆盖。有关更多信息，请参阅User.IsInRole 失败。
应用用户：
public class ApplicationUser : IdentityUser
{
// [StringLength(15)] // do not override UserName, will cause authentication error.
// public new string UserName { get; set; }
public int AcId { get; set; }
public int LcId { get; set; }
// public string ConfirmationToken { get; set; } // Depends on your app if you need to migrate these fields
// public bool IsConfirmed { get; set; }
// public string PasswordResetToken { get; set; }
}