[英]EF Core get Navigation Properties of an entity from Model with multiplicity Zero or One
I am creating a generic class to seed the database with Entities, needed for integration tests. 我正在创建一个通用类,以使用集成测试所需的实体来为数据库添加种子。 I can create individual entities but when one depends from another, I have to manually instruct my class first create the parent entity and then proceed.
我可以创建单个实体,但是当一个实体彼此依赖时,我必须手动指示班级首先创建父实体,然后继续。 I am trying to make this detection automatic, getting from the Model definition, the list of navigation properties with multiplicity 0 or 1 (Reference navigation properties), once that is done, recursively my class will invoke itself to create parent entities first (Circular dependencies are out of scope here).
我试图使这种检测自动进行,从模型定义中获取多重性为0或1的导航属性列表(参考导航属性),一旦完成,递归地我的类将首先调用自身以创建父实体(循环依赖)在此超出范围)。
I used to do this in EF for .net Framework, but EF Core has changed a lot. 我曾经在.net Framework EF中执行此操作,但EF Core发生了很大变化。 What I am missing in EF Core is the RelationshipMultiplicity , I cannot find any reference to Multiplicity in the official documentation, and even tough the hacky solution is to check if the navigation property is a collection, I would like to have more control and keeps things simple.
我在EF Core中缺少的是RelationshipMultiplicity ,我在官方文档中找不到任何对Multiplicity的引用,甚至棘手的解决方案是检查导航属性是否为集合,我想拥有更多控制权并保留所有东西简单。
So far I am exploring the Model definition using: 到目前为止,我正在使用以下方法探索模型定义:
var modelData = _context.Model.GetEntityTypes()
.Select(t => new
{
t.ClrType.Name,
DerivedNavigationProperties = t.FindDerivedNavigations(t.ClrType.Name),
DefiningNavigationProperties = t.FindDefiningNavigation(),
DeclaredForeignKeys = t.GetDeclaredForeignKeys(),
DeclaredNavigations = t.GetDeclaredNavigations(),
DerivedNavigations = t.GetDerivedNavigations(),
DerivedNavigationsInclusive = t.GetDerivedNavigationsInclusive(),
Navigations = t.GetNavigations() // This returns all Navigation Properties (INavigation)
});
After inspecting the source code in GitHub, I can say with enough confidence that there is no such thing as Multiplicity in EF Core. 在检查了GitHub中的源代码之后,我可以很有把握地说,EF Core中没有诸如Multiplicity之类的东西。
I created an enumeration like the one used .net Framework 3.5+ (See: Official documentation ): 我创建了一个枚举,类似于使用的.net Framework 3.5+(请参阅: 官方文档 ):
public enum RelationshipMultiplicity
{
Many = 2,
One = 1,
ZeroOrOne = 0
}
And then an extension method which allows getting all navigation properties using the enum as a filter. 然后是扩展方法,该方法允许使用枚举作为过滤器来获取所有导航属性。 The key things I used are:
我使用的关键是:
The method allows to get all Navigations properties by relation type 该方法允许按关系类型获取所有Navigations属性
public static class ModelExtensions
{
/// <summary>
/// Extension method used to get from the entity all navigation properties by multiplicity
/// </summary>
/// <typeparam name="T">Entity from where the navigation properties are taken</typeparam>
/// <param name="model">Context Model</param>
/// <param name="multiplicity">Type of multiplicity to use</param>
/// <returns>List of PropertyInfo of Navigation Properties</returns>
public static IEnumerable<PropertyInfo> GetNavigationProperties<T>(this IModel model, RelationshipMultiplicity multiplicity)
{
var navigations = model.GetEntityTypes().FirstOrDefault(m => m.ClrType == typeof(T))?.GetNavigations();
var properties = new List<PropertyInfo>();
switch (multiplicity)
{
case RelationshipMultiplicity.Many | RelationshipMultiplicity.ZeroOrOne:
return navigations?
.Select(nav => nav.PropertyInfo);
case RelationshipMultiplicity.Many:
return navigations?
.Where(nav => nav.IsCollection())
.Select(nav => nav.PropertyInfo);
case RelationshipMultiplicity.One:
return navigations?
.Where(nav => !nav.IsCollection() && nav.ForeignKey.IsRequired)
.Select(nav => nav.PropertyInfo);
case RelationshipMultiplicity.ZeroOrOne:
return navigations?
.Where(nav => !nav.IsCollection())
.Select(nav => nav.PropertyInfo);
default:
return null;
}
return properties;
}
}
Usage example: 用法示例:
var oneToManyRelations = _context.Model.GetNavigationProperties<Transaction>(
RelationshipMultiplicity.ZeroOrOne);
var manyToOneRelations = _context.Model.GetNavigationProperties<Transaction>(
RelationshipMultiplicity.Many);
var allRelations = _context.Model.GetNavigationProperties<Transaction>(
RelationshipMultiplicity.Many |
RelationshipMultiplicity.ZeroOrOne);
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