C# 身份实体框架库-更新数据库[MySQL]

我刚刚将库Microsoft.AspNet.Identity.EntityFramework更新为最新版本（2.0.0.0），在创建表时发现一些错误。当我生成迁移代码（Up和Down方法）时，我无法将更改上载到数据库，因为我在执行“updatea database”时遇到了索引问题

指定的密钥太长；最大密钥长度为767字节

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, storeType: "nvarchar"),
                })
            .PrimaryKey(t => t.Id)
            .Index(t => t.Name, unique: true, name: "RoleNameIndex");

        CreateTable(
            "dbo.AspNetUserRoles",
            c => new
                {
                    UserId = c.String(nullable: false, maxLength: 128, storeType: "nvarchar"),
                    RoleId = c.String(nullable: false, maxLength: 128, storeType: "nvarchar"),
                })
            .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",
            c => new
                {
                    Id = c.String(nullable: false, maxLength: 128, storeType: "nvarchar"),
                    Email = c.String(maxLength: 256, storeType: "nvarchar"),
                    EmailConfirmed = c.Boolean(nullable: false),
                    PasswordHash = c.String(maxLength: 256, storeType: "nvarchar"),
                    SecurityStamp = c.String(maxLength: 256, storeType: "nvarchar"),
                    PhoneNumber = c.String(maxLength: 256, storeType: "nvarchar"),
                    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, maxLength: 256, storeType: "nvarchar"),
                })
            .PrimaryKey(t => t.Id)
            .Index(t => t.UserName, unique: true, name: "UserNameIndex");

        CreateTable(
            "dbo.AspNetUserClaims",
            c => new
                {
                    Id = c.Int(nullable: false, identity: true),
                    UserId = c.String(nullable: false, maxLength: 128, storeType: "nvarchar"),
                    ClaimType = c.String(maxLength: 256, storeType: "nvarchar"),
                    ClaimValue = c.String(maxLength: 256, storeType: "nvarchar"),
                })
            .PrimaryKey(t => t.Id)
            .ForeignKey("dbo.AspNetUsers", t => t.UserId, cascadeDelete: true)
            .Index(t => t.UserId);

        CreateTable(
            "dbo.AspNetUserLogins",
            c => new
                {
                    LoginProvider = c.String(nullable: false, maxLength: 128, storeType: "nvarchar"),
                    ProviderKey = c.String(nullable: false, maxLength: 128, storeType: "nvarchar"),
                    UserId = c.String(nullable: false, maxLength: 128, storeType: "nvarchar"),
                })
            .PrimaryKey(t => new { t.LoginProvider, t.ProviderKey, t.UserId })
            .ForeignKey("dbo.AspNetUsers", t => t.UserId, cascadeDelete: true)
            .Index(t => t.UserId);

    }

    public override void Down()
    {
        DropForeignKey("dbo.AspNetUserRoles", "UserId", "dbo.AspNetUsers");
        DropForeignKey("dbo.AspNetUserLogins", "UserId", "dbo.AspNetUsers");
        DropForeignKey("dbo.AspNetUserClaims", "UserId", "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1.0.0.0版本时，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",
            c => new
                {
                    Id = c.String(nullable: false, maxLength: 128, storeType: "nvarchar"),
                    Name = c.String(nullable: false, maxLength: 256, storeType: "nvarchar"),
                })
            .PrimaryKey(t => t.Id);

        CreateTable(
            "dbo.AspNetUsers",
            c => new
                {
                    Id = c.String(nullable: false, maxLength: 128, storeType: "nvarchar"),
                    UserName = c.String(maxLength: 256, storeType: "nvarchar"),
                    PasswordHash = c.String(maxLength: 256, storeType: "nvarchar"),
                    SecurityStamp = c.String(maxLength: 256, storeType: "nvarchar"),
                    Discriminator = c.String(nullable: false, maxLength: 128, storeType: "nvarchar"),
                })
            .PrimaryKey(t => t.Id);

        CreateTable(
            "dbo.AspNetUserClaims",
            c => new
                {
                    Id = c.Int(nullable: false, identity: true),
                    ClaimType = c.String(maxLength: 256, storeType: "nvarchar"),
                    ClaimValue = c.String(maxLength: 256, storeType: "nvarchar"),
                    User_Id = c.String(nullable: false, maxLength: 128, storeType: "nvarchar"),
                })
            .PrimaryKey(t => t.Id)
            .ForeignKey("dbo.AspNetUsers", t => t.User_Id, cascadeDelete: true)
            .Index(t => t.User_Id);

        CreateTable(
            "dbo.AspNetUserLogins",
            c => new
                {
                    UserId = c.String(nullable: false, maxLength: 128, storeType: "nvarchar"),
                    LoginProvider = c.String(nullable: false, maxLength: 128, storeType: "nvarchar"),
                    ProviderKey = c.String(nullable: false, maxLength: 128, storeType: "nvarchar"),
                })
            .PrimaryKey(t => new { t.UserId, t.LoginProvider, t.ProviderKey })
            .ForeignKey("dbo.AspNetUsers", t => t.UserId, cascadeDelete: true)
            .Index(t => t.UserId);

        CreateTable(
            "dbo.AspNetUserRoles",
            c => new
                {
                    UserId = c.String(nullable: false, maxLength: 128, storeType: "nvarchar"),
                    RoleId = c.String(nullable: false, maxLength: 128, storeType: "nvarchar"),
                })
            .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);

    }



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

有人能帮我解决这个问题吗

---

提前谢谢

您可能想查看本教程：

---

-特别是“添加自定义MigrationHistory上下文”一节，它解释了如何设置自定义HistoryContext来解决主键大小问题。

这可能是由于您的数据库使用了

UTF8

排序规则

一种可能的解决方法是将包含

maxLength:256

的代码的所有部分更改为

maxLength:190

---

另一个是将数据库中的

UTF8

排序规则更改为

latin1

或类似的排序规则。

我知道这是一篇老文章，但我今天遇到了同样的问题，并对此进行了一些调查，希望与大家分享我的发现和解决方案

问题在于，Microsoft在两个版本之间为

AspNetRoles

的

Name

列添加了一个唯一的索引，由于该列的大小为256，因此它打破了MySql的索引规则。此问题也会出现在

AspNetUsers

上的

Name

列上

因此，我分析了如何解决这个问题，我认为最正确的做法是减少

Name

列的长度（我认为，没有任何理由让角色/用户的名称这么长）

在研究了IdentityDbContext（基类）上的代码后，我认为解决此问题的最正确方法是覆盖

ApplicationDbContext

中的

OnModelCreating

，并调整其中的列大小，如下所示：

public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
{
    //... default code for ApplicationDbContext

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        if (modelBuilder == null)
        {
            throw new ArgumentNullException("modelBuilder");
        }

        base.OnModelCreating(modelBuilder);

        modelBuilder.Entity<ApplicationUser>().Property(u => u.UserName).HasMaxLength(128);

        //Uncomment this to have Email length 128 too (not neccessary)
        //modelBuilder.Entity<ApplicationUser>().Property(u => u.Email).HasMaxLength(128);

        modelBuilder.Entity<IdentityRole>().Property(r => r.Name).HasMaxLength(128);
    }
}

public类ApplicationDbContext:IdentityDbContext
{
//…ApplicationDbContext的默认代码
模型创建时受保护的覆盖无效（DbModelBuilder modelBuilder）
{
if（modelBuilder==null）
{
抛出新的ArgumentNullException（“modelBuilder”）；
}
基于模型创建（modelBuilder）；
modelBuilder.Entity（）.Property（u=>u.UserName）.HasMaxLength（128）；
//取消对此的注释，使电子邮件长度也达到128（不是必需的）
//modelBuilder.Entity（）.Property（u=>u.Email）.HasMaxLength（128）；
modelBuilder.Entity（）.Property（r=>r.Name）.HasMaxLength（128）；
}
}

此代码将使用

base.OnModelCreating

调用使用默认配置初始化标识模型，然后使用我们自己的调用覆盖在基类中完成的设置

由于您正在创建迁移项目，因此需要重新运行迁移创建以获得更新的模型（或手动修改模型以调整列大小）

这将解决此问题，并且您将拥有Asp.NET标识系统的全部功能

---

当然，为了在创建项目时不出现任何错误，您可以修改迁移代码，但这样您将与您的上下文定义的模型有所不同，这不好，可能会导致问题。

这对我很有效，谢谢您的提示。我只是转到生成的DbMigration文件（其中包含用于创建数据库的所有SQL命令），并将256的每个实例都更改为190。问题解决了！这是目前最好的方法（EF6.1，ASP.NETMVC5）。同意，这是最好的解决方案（EF6，MVC5）。不要忘记删除上次迁移，它是在密钥仍然为256长时生成的。添加上面的代码，删除上次迁移并重新运行Add migration，然后检查迁移代码以查看Name字段的长度现在是128。