abp vnext连接mysql。.net core连接mysql。ef core连接mysql

增加一个MySQL的库:Volo.Abp.EntityFrameworkCore.MySQL

<PackageReference Include="Volo.Abp.EntityFrameworkCore.MySQL" Version="4.4.2" />

然后把UseSqlServer换成UseMySQL

在把上下文对象中的连接字符串修改以下

以为这种就行了？那太天真了

执行迁移命令马上报错：Unable to create an object of type ‘DbContext’. For the different patterns supported at design time。

连接MySQL需要自己重写以下IDesignTimeDbContextFactory接口，配置一点逻辑

public class DesignTimeDbContextFactory : IDesignTimeDbContextFactory<WyJBLandDbContext>
{
    public WyJBLandDbContext CreateDbContext(string[] args)
    {
        var optionsBuilder = new DbContextOptionsBuilder<WyJBLandDbContext>();
        optionsBuilder.UseMySql(ServerVersion.AutoDetect("你的连接字符串"));
        return new WyJBLandDbContext(optionsBuilder.Options);
    }
}

但是如果只是上边那样，虽然执行Add-Migration InitialCreate不会报错，能够正常生成迁移命令但是执行Update-Database就会报错了。

“A relational store has been configured without specifying either the DbConnection or connection string to use.”

只传递一个参数虽然执行迁移命令不会报错，但是执行Update-Database就会报错了。所以需要调用两个参数的方法。
解决方案
在UseMysql上，要传递两个参数（connectionstring，ServerVersion）

贴一下完整的代码，包括读取配置文件的代码

/* This class is needed for EF Core console commands
    * (like Add-Migration and Update-Database commands) */
public class WyJBLandDbContextFactory : IDesignTimeDbContextFactory<WyJBLandDbContext>
{
    public WyJBLandDbContext CreateDbContext(string[] args)
    {
        //BookStoreEfCoreEntityExtensionMappings.Configure();
        var configuration = BuildConfiguration();
        string conn = configuration.GetConnectionString("conn_mysql");
        AddTestLog(conn);
        var builder = new DbContextOptionsBuilder<WyJBLandDbContext>()
            .UseMySql(conn,ServerVersion.AutoDetect(conn));
        return new WyJBLandDbContext(builder.Options);
    }
    /// <summary>
    /// 记录一点内容用于测试连接字符串是否正确获取到
    /// </summary>
    /// <param name="content"></param>
    public void AddTestLog(string content) 
    {
        using (FileStream filestraem = new FileStream("d:/log.txt", FileMode.Append))
        {
            using (StreamWriter write = new StreamWriter(filestraem))
            {
                write.WriteLine(content);
                write.WriteLine("记录时间：" + DateTime.Now.ToString());
                write.WriteLine("----------------------------------------");
                write.Flush();
            }
        }
    }
    private static IConfigurationRoot BuildConfiguration()
    {
        var builder = new ConfigurationBuilder()
            .SetBasePath(Path.Combine(Directory.GetCurrentDirectory(), "../WY.JBLand.API/"))
            .AddJsonFile("appsettings.json", optional: true);
        return builder.Build();
    }
}

还要注意以下mysql连接字符串不能使用.哦，要使用localhost代替否者会报错：
Unable to connect to any of the specified MySQL hosts.