我刚刚将库Microsoft.AspNet.Identity.EntityFramework更新到最后一个版本(2.0.0.0),我发现创建表时出现了一些错误.当我生成迁移代码(向上和向下方法)时,我无法将更改上传到数据库,因为我在执行“Updata-Database”时遇到索引问题

Specified key was too long; max key length is 767 bytes

要执行的代码：

public override void Up()
    {
        CreateTable(
            "dbo.AspNetRoles",c => new
                {
                    Id = c.String(nullable: false,maxLength: 128,storeType: "nvarchar"),Name = c.String(nullable: false,maxLength: 256,})
            .PrimaryKey(t => t.Id)
            .Index(t => t.Name,unique: true,name: "RoleNameIndex");

        CreateTable(
            "dbo.AspNetUserRoles",c => new
                {
                    UserId = c.String(nullable: false,RoleId = c.String(nullable: false,})
            .PrimaryKey(t => new { t.UserId,t.RoleId })
            .ForeignKey("dbo.AspNetRoles",t => t.RoleId,cascadeDelete: true)
            .ForeignKey("dbo.AspNetUsers",t => t.UserId,cascadeDelete: true)
            .Index(t => t.UserId)
            .Index(t => t.RoleId);

        CreateTable(
            "dbo.AspNetUsers",Email = c.String(maxLength: 256,EmailConfirmed = c.Boolean(nullable: false),PasswordHash = c.String(maxLength: 256,SecurityStamp = c.String(maxLength: 256,PhoneNumber = c.String(maxLength: 256,PhoneNumberConfirmed = c.Boolean(nullable: false),TwoFactorEnabled = c.Boolean(nullable: false),LockoutEndDateUtc = c.DateTime(precision: 0),LockoutEnabled = c.Boolean(nullable: false),AccessFailedCount = c.Int(nullable: false),UserName = c.String(nullable: false,})
            .PrimaryKey(t => t.Id)
            .Index(t => t.UserName,name: "UserNameIndex");

        CreateTable(
            "dbo.AspNetUserClaims",c => new
                {
                    Id = c.Int(nullable: false,identity: true),UserId = c.String(nullable: false,ClaimType = c.String(maxLength: 256,ClaimValue = c.String(maxLength: 256,})
            .PrimaryKey(t => t.Id)
            .ForeignKey("dbo.AspNetUsers",cascadeDelete: true)
            .Index(t => t.UserId);

        CreateTable(
            "dbo.AspNetUserLogins",c => new
                {
                    LoginProvider = c.String(nullable: false,ProviderKey = c.String(nullable: false,})
            .PrimaryKey(t => new { t.LoginProvider,t.ProviderKey,t.UserId })
            .ForeignKey("dbo.AspNetUsers",cascadeDelete: true)
            .Index(t => t.UserId);

    }

    public override void Down()
    {
        DropForeignKey("dbo.AspNetUserRoles","UserId","dbo.AspNetUsers");
        DropForeignKey("dbo.AspNetUserLogins","dbo.AspNetUsers");
        DropForeignKey("dbo.AspNetUserClaims","dbo.AspNetUsers");
        DropForeignKey("dbo.AspNetUserRoles","RoleId","dbo.AspNetRoles");
        DropIndex("dbo.AspNetUserLogins",new[] { "UserId" });
        DropIndex("dbo.AspNetUserClaims",new[] { "UserId" });
        DropIndex("dbo.AspNetUsers","UserNameIndex");
        DropIndex("dbo.AspNetUserRoles",new[] { "RoleId" });
        DropIndex("dbo.AspNetUserRoles",new[] { "UserId" });
        DropIndex("dbo.AspNetRoles","RoleNameIndex");
        DropTable("dbo.AspNetUserLogins");
        DropTable("dbo.AspNetUserClaims");
        DropTable("dbo.AspNetUsers");
        DropTable("dbo.AspNetUserRoles");
        DropTable("dbo.AspNetRoles");
    }

当我使用Microsoft.AspNet.Identity.EntityFramework的versión1.0.0.0时,更新数据库的代码是不同的,我没有任何问题

public override void Up()
    {
        CreateTable(
            "dbo.AspNetRoles",})
            .PrimaryKey(t => t.Id);

        CreateTable(
            "dbo.AspNetUsers",UserName = c.String(maxLength: 256,Discriminator = c.String(nullable: false,})
            .PrimaryKey(t => t.Id);

        CreateTable(
            "dbo.AspNetUserClaims",User_Id = c.String(nullable: false,t => t.User_Id,cascadeDelete: true)
            .Index(t => t.User_Id);

        CreateTable(
            "dbo.AspNetUserLogins",LoginProvider = c.String(nullable: false,t.LoginProvider,t.ProviderKey })
            .ForeignKey("dbo.AspNetUsers",cascadeDelete: true)
            .Index(t => t.UserId);

        CreateTable(
            "dbo.AspNetUserRoles",cascadeDelete: true)
            .Index(t => t.UserId)
            .Index(t => t.RoleId);

    }



    public override void Down()
    {
        DropForeignKey("dbo.AspNetUserRoles","RoleNameIndex");
        DropTable("dbo.AspNetUserLogins");
        DropTable("dbo.AspNetUserClaims");
        DropTable("dbo.AspNetUsers");
        DropTable("dbo.AspNetUserRoles");
        DropTable("dbo.AspNetRoles");
    }

任何人都可以帮助我尝试解决问题吗？

提前致谢！！