我对我的所有实体都进行了软删除，并且使用此答案建议的技术不会通过上下文检索软删除的项目。这包括当您通过导航属性访问实体时。
为每个可以软删除的实体添加 IsDeleted 鉴别器。不幸的是，我还没有弄清楚如何根据派生自抽象类或接口的实体来执行此操作（EF 映射当前不支持将接口作为实体）：
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Foo>().Map(m => m.Requires("IsDeleted").HasValue(false));
modelBuilder.Entity<Bar>().Map(m => m.Requires("IsDeleted").HasValue(false));
//It's more complicated if you have derived entities.
//Here 'Block' derives from 'Property'
modelBuilder.Entity<Property>()
.Map<Property>(m =>
{
m.Requires("Discriminator").HasValue("Property");
m.Requires("IsDeleted").HasValue(false);
})
.Map<Block>(m =>
{
m.Requires("Discriminator").HasValue("Block");
m.Requires("IsDeleted").HasValue(false);
});
}
覆盖 SaveChanges 并找到所有要删除的条目：
编辑
另一种覆盖删除sql的方法是更改EF6生成的存储过程
public override int SaveChanges()
{
foreach (var entry in ChangeTracker.Entries()
.Where(p => p.State == EntityState.Deleted
&& p.Entity is ModelBase))//I do have a base class for entities with a single
//"ID" property - all my entities derive from this,
//but you could use ISoftDelete here
SoftDelete(entry);
return base.SaveChanges();
}
SoftDelete 方法直接在数据库上运行 sql，因为鉴别器列不能包含在实体中：
private void SoftDelete(DbEntityEntry entry)
{
var e = entry.Entity as ModelBase;
string tableName = GetTableName(e.GetType());
Database.ExecuteSqlCommand(
String.Format("UPDATE {0} SET IsDeleted = 1 WHERE ID = @id", tableName)
, new SqlParameter("id", e.ID));
//Marking it Unchanged prevents the hard delete
//entry.State = EntityState.Unchanged;
//So does setting it to Detached:
//And that is what EF does when it deletes an item
//http://msdn.microsoft.com/en-us/data/jj592676.aspx
entry.State = EntityState.Detached;
}
GetTableName 返回要为实体更新的表。它处理表链接到 BaseType 而不是派生类型的情况。我怀疑我应该检查整个继承层次结构......但是有计划改进元数据 API，如果我必须研究类型和表之间的 EF 代码优先映射
private readonly static Dictionary<Type, EntitySetBase> _mappingCache
= new Dictionary<Type, EntitySetBase>();
private ObjectContext _ObjectContext
{
get { return (this as IObjectContextAdapter).ObjectContext; }
}
private EntitySetBase GetEntitySet(Type type)
{
type = GetObjectType(type);
if (_mappingCache.ContainsKey(type))
return _mappingCache[type];
string baseTypeName = type.BaseType.Name;
string typeName = type.Name;
ObjectContext octx = _ObjectContext;
var es = octx.MetadataWorkspace
.GetItemCollection(DataSpace.SSpace)
.GetItems<EntityContainer>()
.SelectMany(c => c.BaseEntitySets
.Where(e => e.Name == typeName
|| e.Name == baseTypeName))
.FirstOrDefault();
if (es == null)
throw new ArgumentException("Entity type not found in GetEntitySet", typeName);
_mappingCache.Add(type, es);
return es;
}
internal String GetTableName(Type type)
{
EntitySetBase es = GetEntitySet(type);
//if you are using EF6
return String.Format("[{0}].[{1}]", es.Schema, es.Table);
//if you have a version prior to EF6
//return string.Format( "[{0}].[{1}]",
// es.MetadataProperties["Schema"].Value,
// es.MetadataProperties["Table"].Value );
}
我之前在迁移中使用如下代码在自然键上创建了索引：
public override void Up()
{
CreateIndex("dbo.Organisations", "Name", unique: true, name: "IX_NaturalKey");
}
但这意味着您不能创建与已删除组织同名的新组织。为了允许这样做，我更改了创建索引的代码：
public override void Up()
{
Sql(String.Format("CREATE UNIQUE INDEX {0} ON dbo.Organisations(Name) WHERE IsDeleted = 0", "IX_NaturalKey"));
}
并且从索引中排除已删除的项目
注意
如果相关项目被软删除，则不会填充导航属性，但外键是。例如：
if(foo.BarID != null) //trying to avoid a database call
string name = foo.Bar.Name; //will fail because BarID is not null but Bar is
//but this works
if(foo.Bar != null) //a database call because there is a foreign key
string name = foo.Bar.Name;
PS在此处为全局过滤投票https://entityframework.codeplex.com/workitem/945?FocusElement=CommentTextBox#并在此处过滤