使用EF进行数据库初始化与迁移-优快云博客

本文链接：https://blog.youkuaiyun.com/godlessspirit/article/details/80642720

本文介绍了如何使用Entity Framework（EF）进行数据库初始化和迁移。重点在于`Add-Migration`和`Update-Database`命令的使用，以及在初始化数据时需要注意User、Role、UserRole的填充，特别是`NormalizedEmail`和`NormalizedUserName`字段。还提到了数据库迁移历史记录对后续迁移的影响及解决办法。

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迁移基本步骤参考
dotnet ef migrations add {migration name} -p {dbcontext project} -s {host startup project}
1. 这里的migration name，我以AddData为例：
2. 发现Migrations文件夹下多了两个文件20180610024345_AddData.cs和20180610024345_AddData.Designer.cs
3. 这边我们只关注前一个文件，里面有一个类继承自Migration，它有两个函数Up和Down，且都是空的，熟悉ef的人对这两个函数的大体作用应该比较清楚
4. 数据要初始化主要使用到Up函数的实参MigrationBuilder migrationBuilder,查看源码，这个函数提供了很多有用的函数InsertData UpdateData等

废话不多说，直接上代码

public partial class AddData : Migration
{
    protected override void Up(MigrationBuilder migrationBuilder)
    {
        extra(migrationBuilder);
    }

    private void extra(MigrationBuilder migrationBuilder)
    {
        migrationBuilder.InsertRole(new IdentityRole() { Id = "master_id", Name = "Master", NormalizedName = "Master" });
        migrationBuilder.InsertRole(new IdentityRole() { Id = "admin_id", Name = "Administrator", NormalizedName = "Administrator" });
        migrationBuilder.InsertRole(new IdentityRole() { Id = "vistor_id", Name = "Vistor", NormalizedName = "Vistor" });

        var pwdHasher = new PasswordHasher<IdentityUser>();
        var user = new IdentityUser("DaneSpirit")
        {
            Id = "dane_id",
            NormalizedUserName = "DaneSpirit",
            SecurityStamp = Guid.NewGuid().ToString()
        };
        user.PasswordHash = pwdHasher.HashPassword(user, "danespirit");
        migrationBuilder.InsertSimpleUser(user);

        user = new IdentityUser("TestUser")
        {
            Id = "testuser_id",
            NormalizedUserName = "TestUser",
            SecurityStamp = Guid.NewGuid().ToString()
        };
        user.PasswordHash = pwdHasher.HashPassword(user, "test");
        migrationBuilder.InsertSimpleUser(user);

        migrationBuilder.InsertUserRole(new IdentityUserRole<string>() { UserId = "dane_id", RoleId = "master_id" });
        migrationBuilder.InsertUserRole(new IdentityUserRole<string>() { UserId = "testuser_id", RoleId = "vistor_id" });
    }

    protected override void Down(MigrationBuilder migrationBuilder)
    {

    }
}

我的项目使用了Asp.Net Core Identity，这里我对User、Role、UserRole作了一些基本的初始化，InsertRole InsertSimpleUser InsertUserRole是扩展方法

namespace Microsoft.EntityFrameworkCore.Migrations
{
    static class MigrationBuilderExtensions
    {
        public static OperationBuilder<InsertDataOperation> InsertRole(this MigrationBuilder builder, IdentityRole role)
        {
            var insertDataOperation = new InsertDataOperation()
            {
                Table = "aspnetroles",
                Schema = null,
                Columns = new[] { "id", "name", "NormalizedName", "concurrencystamp" },
                Values = new object[,] { { role.Id, role.Name, role.NormalizedName, role.ConcurrencyStamp } }
            };
            builder.Operations.Add(insertDataOperation);
            return new OperationBuilder<InsertDataOperation>(insertDataOperation);
        }

        public static OperationBuilder<InsertDataOperation> InsertSimpleUser(this MigrationBuilder builder, IdentityUser user)
        {
            var insertDataOperation = new InsertDataOperation()
            {
                Table = "aspnetusers",
                Schema = null,
                Columns = new[] { "id", "username", "NormalizedUserName", "passwordhash", "EmailConfirmed", "AccessFailedCount", "LockoutEnabled", "PhoneNumberConfirmed", "TwoFactorEnabled", "concurrencystamp", "SecurityStamp" },
                Values = new object[,] { { user.Id, user.UserName, user.NormalizedUserName, user.PasswordHash, false, 0, false, false, false, user.ConcurrencyStamp, user.SecurityStamp } }
            };
            builder.Operations.Add(insertDataOperation);
            return new OperationBuilder<InsertDataOperation>(insertDataOperation);
        }

        public static OperationBuilder<InsertDataOperation> InsertUserRole(this MigrationBuilder builder, IdentityUserRole<string> userRole)
        {
            var insertDataOperation = new InsertDataOperation()
            {
                Table = "aspnetuserroles",
                Schema = null,
                Columns = new[] { "userid", "roleid" },
                Values = new object[1, 2] { { userRole.UserId, userRole.RoleId } }
            };
            builder.Operations.Add(insertDataOperation);
            return new OperationBuilder<InsertDataOperation>(insertDataOperation);
        }
    }
}

扩展方法的使用参考了MigrationBuilder的源码
特别注意1：User Role的查询索引都是Normalized*Name，所以咱们的初始化中必须要填充这个字段，否则在后期验证过程中会出现找不到该用户的Exception
特别注意2：User的PasswordHash必须是要经过PasswordHasher.HashPassword函数处理过的，否则也没法在运行时验证通过

dotnet ef database update -p {dbcontext project} -s {host startup project} 不出意外，迁移顺利进行
这里说句题外话，迁移后数据库中会出现一个非自定义表__efmigrationshistory，它是迁移的历史记录，一般情况下，在4中迁移成功后，再次调用4中的命令是不会执行的，主要原因是4的迁移记录已经记录在数据库中，不会发生二次迁移。如果要使4中的命令再次可执行，一个简单的方法是在数据库中将最新的一条迁移历史记录删除。

数据库数据初始化迁移