我遇到了同样的问题，我尝试使用JsonSetting忽略自引用错误，这有点儿麻烦，直到我得到了一个非常自引用的类，并且我的dot-net进程挂在Json编写值上。
我的问题
public partial class Company : BaseModel
{
public Company()
{
CompanyUsers = new HashSet<CompanyUser>();
}
public string Name { get; set; }
public virtual ICollection<CompanyUser> CompanyUsers { get; set; }
}
public partial class CompanyUser
{
public int Id { get; set; }
public int CompanyId { get; set; }
public int UserId { get; set; }
public virtual Company Company { get; set; }
public virtual User User { get; set; }
}
public partial class User : BaseModel
{
public User()
{
CompanyUsers = new HashSet<CompanyUser>();
}
public string DisplayName { get; set; }
public virtual ICollection<CompanyUser> CompanyUsers { get; set; }
}
您可以在引用CompanyUser的 User类中看到问题类，它是一个自引用。
现在，我正在调用包含所有关系属性的GetAll方法。
cs.GetAll("CompanyUsers", "CompanyUsers.User");
在此阶段，我的DotNetCore进程挂在执行JsonResult上，写入值...并永不结束。在我的Startup.cs中，我已经设置了JsonOption。由于某些原因，EFCore包含了我不要求Ef提供的嵌套属性。
options.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
预期的行为应该是这样
嗨，EfCore您能否在我的Company类中也包含“ CompanyUsers”数据，以便我可以轻松访问这些数据。
然后
嗨，EfCore还可以同时包含“ CompanyUsers.User”数据，这样我就可以轻松访问像Company.CompanyUsers.First（）。User.DisplayName这样的数据了
吗？
在此阶段，我应该只获得此“ Company.CompanyUsers.First（）。User.DisplayName”，并且不应给我造成自我引用问题的Company.CompanyUsers.First（）。User.CompanyUsers；从技术上讲，它不应该给我User.CompanyUsers，因为CompanyUsers是导航属性。但是，EfCore感到非常兴奋，并给了我User.CompanyUsers。
因此，我决定编写一种扩展方法，以将属性从对象中排除（实际上不排除它只是将属性设置为null）。不仅如此，它还将对数组属性起作用。下面是我还将为其他用户导出nuget包的代码（不确定是否可以帮助某人）。原因很简单，因为我懒得写.Select（n => new {n.p1，n.p2}）; 我只是不想编写select语句以仅排除1个属性！
这不是最好的代码（我会在某个阶段进行更新），因为我急忙编写，尽管这可能也有助于希望使用数组排除（设置null）对象的人。
public static class PropertyExtensions
{
public static void Exclude<T>(this T obj, Expression<Func<T, object>> expression)
{
var visitor = new PropertyVisitor<T>();
visitor.Visit(expression.Body);
visitor.Path.Reverse();
List<MemberInfo> paths = visitor.Path;
Action<List<MemberInfo>, object> act = null;
int recursiveLevel = 0;
act = (List<MemberInfo> vPath, object vObj) =>
{
// set last propert to null thats what we want to avoid the self-referencing error.
if (recursiveLevel == vPath.Count - 1)
{
if (vObj == null) throw new ArgumentNullException("Object cannot be null");
vObj.GetType().GetMethod($"set_{vPath.ElementAt(recursiveLevel).Name}").Invoke(vObj, new object[] { null });
return;
}
var pi = vObj.GetType().GetProperty(vPath.ElementAt(recursiveLevel).Name);
if (pi == null) return;
var pv = pi.GetValue(vObj, null);
if (pi.PropertyType.IsArray || pi.PropertyType.Name.Contains("HashSet`1") || pi.PropertyType.Name.Contains("ICollection`1"))
{
var ele = (IEnumerator)pv.GetType().GetMethod("GetEnumerator").Invoke(pv, null);
while (ele.MoveNext())
{
recursiveLevel++;
var arrItem = ele.Current;
act(vPath, arrItem);
recursiveLevel--;
}
if (recursiveLevel != 0) recursiveLevel--;
return;
}
else
{
recursiveLevel++;
act(vPath, pv);
}
if (recursiveLevel != 0) recursiveLevel--;
};
// check if the root level propert is array
if (obj.GetType().IsArray)
{
var ele = (IEnumerator)obj.GetType().GetMethod("GetEnumerator").Invoke(obj, null);
while (ele.MoveNext())
{
recursiveLevel = 0;
var arrItem = ele.Current;
act(paths, arrItem);
}
}
else
{
recursiveLevel = 0;
act(paths, obj);
}
}
public static T Explode<T>(this T[] obj)
{
return obj.FirstOrDefault();
}
public static T Explode<T>(this ICollection<T> obj)
{
return obj.FirstOrDefault();
}
}
上面的扩展类将使您能够将属性设置为null以避免自引用循环甚至数组。
表情生成器
internal class PropertyVisitor<T> : ExpressionVisitor
{
public readonly List<MemberInfo> Path = new List<MemberInfo>();
public Expression Modify(Expression expression)
{
return Visit(expression);
}
protected override Expression VisitMember(MemberExpression node)
{
if (!(node.Member is PropertyInfo))
{
throw new ArgumentException("The path can only contain properties", nameof(node));
}
Path.Add(node.Member);
return base.VisitMember(node);
}
}
用途：
模型类
public class Person
{
public string Name { get; set; }
public Address AddressDetail { get; set; }
}
public class Address
{
public string Street { get; set; }
public Country CountryDetail { get; set; }
public Country[] CountryDetail2 { get; set; }
}
public class Country
{
public string CountryName { get; set; }
public Person[] CountryDetail { get; set; }
}
虚拟数据
var p = new Person
{
Name = "Adeel Rizvi",
AddressDetail = new Address
{
Street = "Sydney",
CountryDetail = new Country
{
CountryName = "AU"
}
}
};
var p1 = new Person
{
Name = "Adeel Rizvi",
AddressDetail = new Address
{
Street = "Sydney",
CountryDetail2 = new Country[]
{
new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A1" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A2" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A3" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A4" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A5" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A6" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A7" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A8" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A9" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A1" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A2" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A3" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A4" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A5" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A6" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A7" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A8" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
new Country{ CountryName = "AU", CountryDetail = new Person[]{ new Person { Name = "A9" }, new Person { Name = "A1" }, new Person { Name = "A1" } } },
}
}
};
情况：
情况1：仅排除没有任何数组的属性
p.Exclude(n => n.AddressDetail.CountryDetail.CountryName);
情况2：排除具有1个数组的属性
p1.Exclude(n => n.AddressDetail.CountryDetail2.Explode().CountryName);
情况3：排除具有2个嵌套数组的属性
p1.Exclude(n => n.AddressDetail.CountryDetail2.Explode().CountryDetail.Explode().Name);
情况4：包含的EF GetAll查询
var query = cs.GetAll("CompanyUsers", "CompanyUsers.User").ToArray();
query.Exclude(n => n.Explode().CompanyUsers.Explode().User.CompanyUsers);
return query;
您已经注意到Explode（）方法也是它的扩展方法，仅用于表达式构建器从数组属性获取属性。每当有数组属性时，请使用.Explode（）。YourPropertyToExclude或.Explode（）。Property1.MyArrayProperty.Explode（）。MyStupidProperty。上面的代码帮助我避免了自我引用的深度。现在，我可以使用GetAll并排除我不想要的属性！
感谢您阅读这篇重要文章！