我建议EF的数据库迁移, 还是统一弄成跟配置文件一致. 已经附上代码

在代码里的DataContextFactory写DBConnStr, 万一那天改了配置文件, 代码里忘了改了,那不是出大问题了?
我建议让DataContextFactory直接读配置文件. 当前只测试了sqlserver,其他没测. 需要的朋友自己加就行了.

```csharp
public class DataContextFactory : IDesignTimeDbContextFactory
{
public DataContext CreateDbContext(string[] args)
{
var cfgJson = new ConfigurationBuilder().AddJsonFile("appsettings.json").Build();

var dbconnstr = cfgJson.GetSection("Connections:0:Value").Value;
var dbtype = cfgJson.GetSection("Connections:0:DBType").Value;
var db2 = cfgJson.GetSection("Connections:1:Value").Value;

Debug.Assert(db2 == null, "当前EF database迁移仅支持一个数据库");
Debug.Assert(dbconnstr != null, "appsettings.json 必须已经设定好Connections节的Value");
Debug.Assert(dbtype != null, "appsettings.json 必须已经设定好Connections节的dbtype");
Debug.Assert(dbtype == "SqlServer", "当前EF database仅支持sqlserver");

return new DataContext(dbconnstr, DBTypeEnum.SqlServer);
}
}
```