我有一个实现了数据库中软删除的框架（使用可空的 DateTime，称为 DeletedDate）。我正在使用仓储来处理主要的实体请求，如下所示：
/// <summary>
/// Returns a Linq Queryable instance of the entity collection.
/// </summary>
public IQueryable<T> All
{
get { return Context.Set<T>().Where(e => e.DeletedDate == null); }
}
这个很好用，但是我遇到的问题是当你包含导航属性时，如何确保只查询活动记录。相关的存储库方法开头如下：
/// <summary>
/// Returns a Linq Queryable instance of the entity collection, allowing connected objects to be loaded.
/// </summary>
/// <param name="includeProperties">Connected objects to be included in the result set.</param>
/// <returns>An IQueryable collection of entity.</returns>
public IQueryable<T> AllIncluding(params Expression<Func<T, object>>[] includeProperties)
{
IQueryable<T> query = Context.Set<T>().Where(e => e.DeletedDate == null);
foreach (var includeProperty in includeProperties)
{
query = query.Include(includeProperty);
}
return query;
}
如果实体Parent正在使用一个名为Children的导航属性，则AllIncluding方法将正确过滤掉软删除的Parent记录，但软删除的Children记录仍将被包括。
查看发送到数据库的查询，似乎只需要在sql join子句中添加“AND Children.DeletedDate IS NULL”，查询就会返回正确的结果。
在我的研究中，我发现了这篇帖子 ，它似乎正是我所需要的，但我的实现没有获得与帖子作者相同的结果。通过代码逐步执行，似乎对查询的Children部分没有任何影响。
以下是我当前相关的代码（注意：使用NuGet中的QueryInterceptor）：
基础类：
using System;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
namespace DomainClasses
{
/// <summary>
/// Serves as the Base Class for All Data Model Classes
/// </summary>
public class BaseClass
{
/// <summary>
/// Default constructor, sets EntityState to Unchanged.
/// </summary>
public BaseClass()
{
this.StateOfEntity = DomainClasses.StateOfEntity.Unchanged;
}
/// <summary>
/// Indicates the current state of the entity. Not mapped to Database.
/// </summary>
[NotMapped]
public StateOfEntity StateOfEntity { get; set; }
/// <summary>
/// The entity primary key.
/// </summary>
[Key, Column(Order = 0), ScaffoldColumn(false)]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
/// <summary>
/// The date the entity record was created. Updated in InsightDb.SaveChanges() method
/// </summary>
[Column(Order = 1, TypeName = "datetime2"), ScaffoldColumn(false)]
public DateTime AddDate { get; set; }
/// <summary>
/// The UserName of the User who created the entity record. Updated in InsightDb.SaveChanges() method
/// </summary>
[StringLength(56), Column(Order = 2), ScaffoldColumn(false)]
public string AddUser { get; set; }
/// <summary>
/// The date the entity record was modified. Updated in InsightDb.SaveChanges() method
/// </summary>
[Column(Order = 3, TypeName = "datetime2"), ScaffoldColumn(false)]
public DateTime ModDate { get; set; }
/// <summary>
/// The UserName of the User who modified the entity record.
/// </summary>
[StringLength(56), Column(Order = 4), ScaffoldColumn(false)]
public string ModUser { get; set; }
/// <summary>
/// Allows for Soft Delete of records.
/// </summary>
[Column(Order = 5, TypeName = "datetime2"), ScaffoldColumn(false)]
public DateTime? DeletedDate { get; set; }
}
}
父类：
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
namespace DomainClasses
{
/// <summary>
/// The Parent Entity.
/// </summary>
public class Parent : BaseClass
{
/// <summary>
/// Instantiates a new instance of Parent, initializes the virtual sets.
/// </summary>
public Parent()
{
this.Children = new HashSet<Child>();
}
#region Properties
/// <summary>
/// The Parent's Name
/// </summary>
[StringLength(50), Required, Display(Name="Parent Name")]
public string Name { get; set; }
#endregion
#region Relationships
/// <summary>
/// Relationship to Child, 1 Parent = Many Children.
/// </summary>
public virtual ICollection<Child> Children { get; set; }
#endregion
}
}
子类：
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
namespace DomainClasses
{
/// <summary>
/// The Child entity. One Parent = Many Children
/// </summary>
public class Child : BaseClass
{
#region Properties
/// <summary>
/// Child Name.
/// </summary>
[Required, StringLength(50), Display(Name="Child Name")]
public string Name { get; set; }
#endregion
#region Relationships
/// <summary>
/// Parent Relationship. 1 Parent = Many Children.
/// </summary>
public virtual Parent Parent { get; set; }
#endregion
}
}
上下文类：
using DomainClasses;
using System;
using System.Data;
using System.Data.Entity;
using System.Linq;
namespace DataLayer
{
public class DemoContext : DbContext, IDemoContext
{
/// <summary>
/// ActiveSession object of the user performing the action.
/// </summary>
public ActiveSession ActiveSession { get; private set; }
public DemoContext(ActiveSession activeSession)
: base("name=DemoDb")
{
ActiveSession = activeSession;
this.Configuration.LazyLoadingEnabled = false;
}
#region Db Mappings
public IDbSet<Child> Children { get; set; }
public IDbSet<Parent> Parents { get; set; }
#endregion
public override int SaveChanges()
{
var changeSet = ChangeTracker.Entries<BaseClass>();
if (changeSet != null)
{
foreach (var entry in changeSet.Where(c => c.State != EntityState.Unchanged))
{
entry.Entity.ModDate = DateTime.UtcNow;
entry.Entity.ModUser = ActiveSession.UserName;
if (entry.State == EntityState.Added)
{
entry.Entity.AddDate = DateTime.UtcNow;
entry.Entity.AddUser = ActiveSession.UserName;
}
else if (entry.State == EntityState.Deleted)
{
entry.State = EntityState.Modified;
entry.Entity.DeletedDate = DateTime.UtcNow;
}
}
}
return base.SaveChanges();
}
public new IDbSet<T> Set<T>() where T : BaseClass
{
return ((DbContext)this).Set<T>();
}
}
}
仓库类：
using DomainClasses;
using QueryInterceptor;
using System;
using System.Data.Entity;
using System.Linq;
using System.Linq.Expressions;
namespace DataLayer
{
/// <summary>
/// Entity Repository to be used in Business Layer.
/// </summary>
public class EntityRepository<T> : IEntityRepository<T> where T : BaseClass
{
public IDemoContext Context { get; private set; }
/// <summary>
/// Main Constructor for Repository. Creates an instance of DemoContext (derives from DbContext).
/// </summary>
/// <param name="activeSession">UserName of the User performing the action.</param>
public EntityRepository(ActiveSession activeSession)
: this(new DemoContext(activeSession))
{
}
/// <summary>
/// Constructor for Repository. Allows a context (i.e. FakeDemoContext) to be passed in for testing.
/// </summary>
/// <param name="context">IDemoContext to be used in the repository. I.e. FakeDemoContext.</param>
public EntityRepository(IDemoContext context)
{
Context = context;
}
/// <summary>
/// Returns a Linq Queryable instance of the entity collection.
/// </summary>
public IQueryable<T> All
{
get { return Context.Set<T>().Where(e => e.DeletedDate == null); }
}
/// <summary>
/// Returns a Linq Queryable instance of the entity collection, allowing connected objects to be loaded.
/// </summary>
/// <param name="includeProperties">Connected objects to be included in the result set.</param>
/// <returns>An IQueryable collection of entity.</returns>
public IQueryable<T> AllIncluding(params Expression<Func<T, object>>[] includeProperties)
{
IQueryable<T> query = Context.Set<T>().Where(e => e.DeletedDate == null);
InjectConditionVisitor icv = new InjectConditionVisitor();
foreach (var includeProperty in includeProperties)
{
query = query.Include(includeProperty);
}
return query.InterceptWith(icv);
}
/// <summary>
/// Finds a single instance of the entity by the Id.
/// </summary>
/// <param name="id">The primary key for the entity.</param>
/// <returns>An instance of the entity.</returns>
public T Find(int id)
{
return Context.Set<T>().Where(e => e.DeletedDate == null).SingleOrDefault(e => e.Id == id);
}
/// <summary>
/// Takes a single entity or entity graph and reads the explicit state, then applies the necessary State changes to Update or Add the entities.
/// </summary>
/// <param name="entity">The entity object.</param>
public void InsertOrUpdate(T entity)
{
if (entity.StateOfEntity == StateOfEntity.Added)
{
Context.Set<T>().Add(entity);
}
else
{
Context.Set<T>().Add(entity);
Context.ApplyStateChanges();
}
}
/// <summary>
/// Deletes the instance of the entity.
/// </summary>
/// <param name="id">The primary key of the entity.</param>
public void Delete(int id)
{
var entity = Context.Set<T>().Where(e => e.DeletedDate == null).SingleOrDefault(e => e.Id == id);
entity.StateOfEntity = StateOfEntity.Deleted;
Context.Set<T>().Remove(entity);
}
/// <summary>
/// Saves the transaction.
/// </summary>
public void Save()
{
Context.SaveChanges();
}
/// <summary>
/// Disposes the Repository.
/// </summary>
public void Dispose()
{
Context.Dispose();
}
}
}
InjectConditionVisitor Class:
using System;
using System.Linq;
using System.Linq.Expressions;
namespace DataLayer
{
public class InjectConditionVisitor : ExpressionVisitor
{
private QueryConditional queryCondition;
public InjectConditionVisitor(QueryConditional condition)
{
queryCondition = condition;
}
public InjectConditionVisitor()
{
queryCondition = new QueryConditional(x => x.DeletedDate == null);
}
protected override Expression VisitMember(MemberExpression ex)
{
// Only change generic types = Navigation Properties
// else just execute the normal code.
return !ex.Type.IsGenericType ? base.VisitMember(ex) : CreateWhereExpression(queryCondition, ex) ?? base.VisitMember(ex);
}
/// <summary>
/// Create the where expression with the adapted QueryConditional
/// </summary>
/// <param name="condition">The condition to use</param>
/// <param name="ex">The MemberExpression we're visiting</param>
/// <returns></returns>
private Expression CreateWhereExpression(QueryConditional condition, Expression ex)
{
var type = ex.Type;//.GetGenericArguments().First();
var test = CreateExpression(condition, type);
if (test == null)
return null;
var listType = typeof(IQueryable<>).MakeGenericType(type);
return Expression.Convert(Expression.Call(typeof(Enumerable), "Where", new Type[] { type }, (Expression)ex, test), listType);
}
/// <summary>
/// Adapt a QueryConditional to the member we're currently visiting.
/// </summary>
/// <param name="condition">The condition to adapt</param>
/// <param name="type">The type of the current member (=Navigation property)</param>
/// <returns>The adapted QueryConditional</returns>
private LambdaExpression CreateExpression(QueryConditional condition, Type type)
{
var lambda = (LambdaExpression)condition.Conditional;
var conditionType = condition.Conditional.GetType().GetGenericArguments().FirstOrDefault();
// Only continue when the condition is applicable to the Type of the member
if (conditionType == null)
return null;
if (!conditionType.IsAssignableFrom(type))
return null;
var newParams = new[] { Expression.Parameter(type, "bo") };
var paramMap = lambda.Parameters.Select((original, i) => new { original, replacement = newParams[i] }).ToDictionary(p => p.original, p => p.replacement);
var fixedBody = ParameterRebinder.ReplaceParameters(paramMap, lambda.Body);
lambda = Expression.Lambda(fixedBody, newParams);
return lambda;
}
}
}
QueryConditional 类：
using DomainClasses;
using System;
using System.Linq.Expressions;
namespace DataLayer
{
public class QueryConditional
{
public QueryConditional(Expression<Func<BaseClass, bool>> ex)
{
Conditional = ex;
}
public Expression<Func<BaseClass, bool>> Conditional { get; set; }
}
}
参数重新绑定类：
using System.Collections.Generic;
using System.Linq.Expressions;
namespace DataLayer
{
public class ParameterRebinder : ExpressionVisitor
{
private readonly Dictionary<ParameterExpression, ParameterExpression> map;
public ParameterRebinder(Dictionary<ParameterExpression, ParameterExpression> map)
{
this.map = map ?? new Dictionary<ParameterExpression, ParameterExpression>();
}
public static Expression ReplaceParameters(Dictionary<ParameterExpression, ParameterExpression> map, Expression exp)
{
return new ParameterRebinder(map).Visit(exp);
}
protected override Expression VisitParameter(ParameterExpression node)
{
ParameterExpression replacement;
if (map.TryGetValue(node, out replacement))
node = replacement;
return base.VisitParameter(node);
}
}
}
IEntityRepository 接口：
using System;
using System.Linq;
using System.Linq.Expressions;
namespace DataLayer
{
public interface IEntityRepository<T> : IDisposable
{
IQueryable<T> All { get; }
IQueryable<T> AllIncluding(params Expression<Func<T, object>>[] includeProperties);
T Find(int id);
void InsertOrUpdate(T entity);
void Delete(int id);
void Save();
}
}
IDemoContext接口：
using DomainClasses;
using System;
using System.Data.Entity;
namespace DataLayer
{
public interface IDemoContext : IDisposable
{
ActiveSession ActiveSession { get; }
IDbSet<Child> Children { get; }
IDbSet<Parent> Parents { get; }
int SaveChanges();
IDbSet<T> Set<T>() where T : BaseClass;
}
}