概要：有点老套，因为早在 .net frmework的时候（core还没出来），我们在使用 ef(4.。。。6)的时候就已经这么用，这里我在搭建框架，所以随手写下，让后来人直接拿去用用。
1.使用前提
使用前我们一定要明白的是，通过fluent api去映射实体关系和属性的，也就是说core里面，要实现IEntityTypeConfiguration<TEntity>接口对象，示例如下：
public class UserRoleConfiguration : IEntityTypeConfiguration<UserRole>
{
public override void Configure(EntityTypeBuilder<UserRole> builder)
{
builder.HasMany(x => x.UserRolePermissionCollection).WithOne(x => x.UserRole).HasForeignKey(x => x.UserRoleID).IsRequired();
builder.HasDataRole();
}
}
这时候我们可以在 DBContext的 onModelCreating中如下方式注入：
public class DbContextBase : DbContext, IDbContext
{
private readonly IEntityConfigurationFinder _configurationFinder;
public DbContextBase(DbContextOptions options, IEntityConfigurationFinder configurationFinder)
: base(options)
{
_configurationFinder = configurationFinder;
} protected override void OnModelCreating(ModelBuilder modelBuilder)
{
Type contextType = GetType();
IEntityRegister[] entityConfigures = _configurationFinder.GetEntityRegisters();
foreach (var config in entityConfigures)
{
config.Apply(modelBuilder);
}
}
}
这是其中一个实体的映射方式，假设我们有十几或几十个，那么我们需要在这些十几或者几十遍，累得慌吧，累就对了，所以换个方式实现：
我们在定义一个IEntityRegister对象，所有的 所有实体映射类都需要实现这个接口对象，接口如下：
public interface IEntityRegister
{
void Apply(ModelBuilder builder);
}
同时修改上面的 roleEntityTypeConfiguration
public class UserRoleConfiguration : IEntityTypeConfiguration<UserRole>,IEntityRegister
{
public override void Configure(EntityTypeBuilder<UserRole> builder)
{
builder.HasMany(x => x.UserRolePermissionCollection).WithOne(x => x.UserRole).HasForeignKey(x => x.UserRoleID).IsRequired();
builder.HasDataRole();
}
public void Apply(ModelBuilder modelBuilder){
modelBuilder.ApplyConfiguration(this);
}
}
这时候我们其他的几十个 实体的配置对象，依旧按照如上写法即可，现在我们要做的就是找到所有实现了IEntityRegister接口的对象，也就是实体的映射对象。
2.查找实体配置对象
之前我们在上一篇说 dependencyInjection对象的时候，有写过一个类，其中查找程序及对象的方法，这里我们就又用到了，再贴一次完整的：
接口实现：
/// <summary>
/// 查找应用程序中的程序集对象
/// </summary>
public interface IAppAssemblyFinder
{
/// <summary>
/// 查询所有程序集对象
/// </summary>
/// <param name="filterAssembly">是否排除非业务程序集对象</param>
/// <returns></returns>
Assembly[] FindAllAssembly(bool filterAssembly = true);
/// <summary>
/// 获取指定类型的对象集合
/// </summary>
/// <typeparam name="ItemType">指定的类型</typeparam>
/// <param name="expression">
/// 过滤表达式:
/// 查询接口(type=>typeof(ItemType).IsAssignableFrom(type));
/// 查询实体:type => type.IsDeriveClassFrom<ItemType>()
/// </param>
/// <param name="fromCache">是否从缓存查询</param>
/// <returns></returns>
Type[] FindTypes<ItemType>(Func<Type, bool> expression, bool fromCache = true) where ItemType : class;
}
对应实现类：
public class AppAssemblyFinder : IAppAssemblyFinder
{
private List<Assembly> _assemblies = new List<Assembly>(); public Assembly[] FindAllAssembly(bool filterAssembly = true)
{
var filter = new string[]{
"System",
"Microsoft",
"netstandard",
"dotnet",
"Window",
"mscorlib",
"Newtonsoft",
"Remotion.Linq"
};
//core中获取依赖对象的方式
DependencyContext context = DependencyContext.Default;
if (context != null)
{
List<string> names = new List<string>();
string[] dllNames = context.CompileLibraries.SelectMany(m => m.Assemblies).Distinct().Select(m => m.Replace(".dll", "")).ToArray();
if (dllNames.Length > )
{
names = (from name in dllNames
let index = name.LastIndexOf('/') +
select name.Substring(index))
.Distinct()
.WhereIf(name => !filter.Any(name.StartsWith), filterAssembly)
.ToList();
}
return LoadFromFiles(names);
}
//传统方式
string pathBase = AppDomain.CurrentDomain.BaseDirectory;
string[] files = Directory.GetFiles(pathBase, "*.dll", SearchOption.TopDirectoryOnly)
.Concat(Directory.GetFiles(pathBase, ".exe", SearchOption.TopDirectoryOnly))
.ToArray();
if (filterAssembly)
{
files = files.WhereIf(f => !filter.Any(n => f.StartsWith(n, StringComparison.OrdinalIgnoreCase)), filterAssembly).Distinct().ToArray();
}
_assemblies = files.Select(Assembly.LoadFrom).ToList();
return _assemblies.ToArray();
} /// <summary>
/// 获取指定类型的对象集合
/// </summary>
/// <typeparam name="ItemType">指定的类型</typeparam>
/// <param name="expression"> 过滤表达式: 查询接口(type=>typeof(ItemType).IsAssignableFrom(type)); 查询实体:type => type.IsDeriveClassFrom<ItemType>()</param>
/// <param name="fromCache">是否从缓存查询</param>
/// <returns></returns>
public Type[] FindTypes<ItemType>(Func<Type, bool> expression, bool fromCache = true) where ItemType : class
{
List<Assembly> assemblies;
if (fromCache) assemblies = _assemblies;
if (_assemblies == null || _assemblies.Count() == )
assemblies = this.FindAllAssembly().ToList(); Type[] types = _assemblies.SelectMany(a => a.GetTypes())
.Where(expression).Distinct().ToArray(); return types;
}
/// <summary>
/// 从文件加载程序集对象
/// </summary>
/// <param name="files">文件(名称集合)</param>
/// <returns></returns>
private static Assembly[] LoadFromFiles(List<string> files)
{
List<Assembly> assemblies = new List<Assembly>();
files?.ToList().ForEach(f =>
{
AssemblyName name = new AssemblyName(f);
try { Assembly assembly = Assembly.Load(name); assemblies.Add(assembly); } catch { }
});
return assemblies.ToArray();
} }
需要注意的是，这个接口以及实现类，需要注册为 singleton对象，保证生命周期和应用程序一致，否则，参数的fromCache无效，性能也会急剧下降。
查找IEntityRegister对象：
public class EntityConfigFinder : IEntityConfigFinder
{
public EntityConfigFinder(IAppAssemblyFinder assemblyFinder)
{
_assemblyFinder = assemblyFinder;
} private readonly IAppAssemblyFinder _assemblyFinder; public IEntityRegister[] EntityRegisters()
{
var baseType = typeof(IEntityRegister);
var types = _assemblyFinder.FindTypes<IEntityRegister>(type => baseType.IsAssignableFrom(type));
var entityRegisters = types.Select(t => (IEntityRegister)Activator.CreateInstance(t))?.ToArray();
return entityRegisters;
}
}
这时候我们就可以很简单的使用了：
3.使用
public class DbContextBase : DbContext, IDbContext
{
public DbContextBase(DbContextOptions options, IEntityConfigFinder entityFinder)
: base(options)
{
_entityConfigFinder = entityFinder;
} private readonly IEntityConfigFinder _entityConfigFinder; protected override void OnModelCreating(ModelBuilder modelBuilder)
{
var dbContextType = GetType();
IEntityRegister[] entityRegisters = _entityConfigFinder.EntityRegisters();
foreach (var entityConfig in entityRegisters)
{
entityConfig.RegistTo(modelBuilder);
Console.WriteLine($"成功注册实体:{entityConfig.EntityType}");
}
Console.WriteLine($"成功注册实体:{entityRegisters.Length}个");
}
}
}
4.其他
在 ef(6.x)中我们使用EntityTypeConfiguration的时候，可以直接使用该对象，但是core中没有了，所以我们可以再封装一个实现类：
public abstract class EntityTypeConfigurationBase<TEntity, TKey> : IEntityTypeConfiguration<TEntity>, IEntityRegister
where TEntity : class, IEntity<TKey>
{
/// <summary>
/// 将当前实体类映射对象注册到数据上下文模型构建器中
/// </summary>
/// <param name="modelBuilder">上下文模型构建器</param>
public void Apply(ModelBuilder modelBuilder)
{
modelBuilder.ApplyConfiguration(this);
} /// <summary>
/// 重写以实现实体类型各个属性的数据库配置
/// </summary>
/// <param name="builder">实体类型创建器</param>
public abstract void Configure(EntityTypeBuilder<TEntity> builder);
}
这时候，我们的实体的配置类只需要继承该类，并实现其方法就可以了，比如：
public class UserRoleConfiguration : EntityTypeConfigurationBase<UserRole, Guid>
{
public override void Configure(EntityTypeBuilder<UserRole> builder)
{
builder.HasMany(x => x.UserRolePermissionCollection).WithOne(x => x.UserRole).HasForeignKey(x => x.UserRoleID).IsRequired();
builder.HasDataRole();
}
}
DbContext的 OnModelCreating中不变。
结束！