在我的代码中的多个地方,我正在使用方便的dandy @UseFilters(UnprocessableEntityExceptionFilter)
export class EventsController {}
扩展名进行批量更新,例如
Z.EntityFramework.Plus
这将更新await db.Foos
.Where(f => f.SomeCondition)
.UpdateAsync(f => new Foo { Field1 = "bar", Field2 = f.Field2 + 1 });
为真的所有Foo
记录,将SomeCondition
设置为“ bar”,而Field1
将增加1。
现在提出了一个新要求,其中某些表(但不是全部)正在跟踪Field2
。其中包括我正在进行批量更新的记录。
所以我的方法是这样的。我有一个界面:
ModifiedDate
因此,我跟踪public interface ITrackModifiedDate
{
DateTime ModifiedDate { get; set; }
}
的所有类都可以实现ModifiedDate
。然后,我编写一个中间人扩展名以拦截ITrackModifiedDate
调用:
.UpdateAsync()
如您所见,除了已经更新的其他任何字段之外,我还不确定如何修改public static async Task<int> UpdateAsync<T>(this IQueryable<T> queryable, Expression<Func<T, T>> updateFactory)
where T : class
{
if (typeof(ITrackModifiedDate).IsAssignableFrom(typeof(T)))
{
// TODO Now what?
}
return await BatchUpdateExtensions.UpdateAsync(queryable, updateFactory);
}
以将updateFactory
设置为ModifiedDate
。
如何做到?
更新:我不反对更改扩展名,以使其只接受类型为DateTime.UtcNow
的{{1}},如果可以的话,即
T
答案 0 :(得分:1)
我通过以下代码使用它:
using System;
using System.Data.Entity;
using System.Linq;
using System.Linq.Expressions;
using System.Threading.Tasks;
using Z.EntityFramework.Plus;
class Program
{
static async Task Main(string[] args)
{
using (var context = new SomeContext())
{
await context
.Customers
.Where(c => c.Email.Contains("42"))
.CustomUpdateAsync((c) => new Customer()
{
Email = "4242"
});
}
}
}
public static class Helper
{
public static async Task<int> CustomUpdateAsync<T>(this IQueryable<T> queryable, Expression<Func<T, T>> updateFactory)
where T : class
{
var targetType = typeof(T);
if (typeof(ITrackModifiedDate).IsAssignableFrom(targetType))
{
updateFactory = (Expression<Func<T, T>>)new TrackModifiedDateVisitor().Modify(updateFactory);
}
return await BatchUpdateExtensions.UpdateAsync(queryable, updateFactory);
}
}
public class TrackModifiedDateVisitor : ExpressionVisitor
{
public Expression Modify(Expression expression)
{
return Visit(expression);
}
public override Expression Visit(Expression node)
{
if (node is MemberInitExpression initExpression)
{
var existingBindings = initExpression.Bindings.ToList();
var modifiedProperty = initExpression.NewExpression.Type.GetProperty(nameof(ITrackModifiedDate.ModifiedDate));
// it will be `some.ModifiedDate = currentDate`
var modifiedExpression = Expression.Bind(
modifiedProperty,
Expression.Constant(DateTime.Now, typeof(DateTime))
);
existingBindings.Add(modifiedExpression);
// and then we just generate new MemberInit expression but with additional property assigment
return base.Visit(Expression.MemberInit(initExpression.NewExpression, existingBindings));
}
return base.Visit(node);
}
}
public class SomeContext: DbContext
{
public SomeContext()
: base("Data Source=.;Initial Catalog=TestDb;Integrated Security=SSPI;")
{
Database.SetInitializer(new CreateDatabaseIfNotExists<SomeContext>());
}
public DbSet<Customer> Customers { get; set; }
}
public class Customer: ITrackModifiedDate
{
public int ID { get; set; }
public string Email { get; set; }
public DateTime ModifiedDate { get; set; }
}
public interface ITrackModifiedDate
{
DateTime ModifiedDate { get; set; }
}
需要的部分是TrackModifiedDateVisitor
类,它遍历updateFactory
表达式并在找到MemberInitExpression
并进行更新时进行遍历。最初,它具有属性分配的列表,我们为ModifiedDate
生成一个新属性,并使用现有的属性加上生成的属性创建新的MemberInitExpression
。
执行访问者代码后的结果-updateFactory
将具有
c => new Customer() {Email = "4242", ModifiedDate = 5/16/2019 23:19:00}