从实体框架类获取默认的SQL值 [英] Get default sql value from Entity Framework class

问题描述

我正在使用从此答案中提出的模板稍作修改的T4模板，以从我的EF POCO生成打字稿界面

I am using a T4 template slightly modified from the one proposed in this answer to generate typescript interfaces from my EF POCOs.

EF核心POCO首先生成数据库，并且某些数据库列具有默认值。这些由EF生成器正确映射到我的上下文中，例如 .HasDefaultValueSql（ 0）;

The EF Core POCOs were generated database first, and some of the database columns have default values. These are correctly mapped by the EF generator into my context, e.g. .HasDefaultValueSql("0");

我对如何访问默认值有些困惑给定EF类的值，我曾想过 GetValueOrDefault 可以解决问题，但这只是为.net类型提供默认值。

I'm a little confused about how to go about accessing the default value for a given EF class, i had thought GetValueOrDefault might do the trick but that's just giving the default value for the .net type.

我看到还有其他一些解决方案可以使此工作正常进行，但我似乎找不到能与ASP .Net Core一起使用的解决方案。

I see there are some other solutions out there for getting this working but i can't seem to find one that yet works with ASP .Net Core.

理想情况下，我想知道如何从其MemberInfo中确定某个属性是否具有默认EF值，因为T4模板的以下行正在生成属性描述，因此最容易修改该属性以输出默认值

Ideally, i would like to know how to determine if a property has a default EF value from it's MemberInfo, as the following line from the T4 template is generating the property descriptions it would be the easiest to modify that to output a default value for the TypeScript def.

foreach (MemberInfo mi in GetInterfaceMembers(t))
{
    sb.AppendFormat("  {0}: {1};\n", mi.Name, GetTypeName(mi));
}

推荐答案

如果您有权访问生成的 DbContext ，您可以使用 DbContext.Model 提供的元数据来代替反射。

In case you have access to the generated DbContext, you can use the metadata provided by the DbContext.Model instead of reflection.

例如：

foreach (var type in db.Model.GetEntityTypes())
{
    foreach (var property in type.GetProperties())
    {
        var defaultValue = property.Relational().DefaultValue;
    }
}

还有很多有用的方法，例如 IModel.FindEntityType ， IEnityType.FindProperty 等

There are also a lot of useful methods like IModel.FindEntityType, IEnityType.FindProperty etc.

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