由于对象的当前状态，IEquatable操作无效

Ad I'm developping a project in C# I recently came over an error I can't understand.

我正在用c#开发一个项目，最近我遇到了一个我无法理解的错误。

First of all here is the core

首先这里是核心

if (CanPlay(target.Coord.X, target.Coord.Y))
{
    target.Owner = m.Player;
    this.MoveList.Push(m);
    // Groupes
    var friends = GetAround(target).FindAll(i => i.Owner == target.Owner);

    Groupe g = new Groupe { target };
    foreach (Intersection fr in friends)
    {
        g.AddRange(GetGroupe(fr));
    }
    foreach (Intersection fr in friends)
    {
        this.Groupes.Remove(GetGroupe(fr));
    }
    this.Groupes.Add(g);
}

And here is the getGroupe function that causes the problem :

这是导致问题的getGroupe函数:

Groupe GetGroupe(Intersection i)
{
    return this.Groupes.First(g => g.Contains(i));
}

So, at some random moments, when a move is done, I get the IEquatable Operation is not valid due to the current state of the object. Here is the stack trace :

因此，在某些随机时刻，当移动完成时，由于对象的当前状态，我得到IEquatable操作无效。这是堆栈跟踪:

InvalidOperationException: Operation is not valid due to the current state of the object
System.Linq.Enumerable.First[Groupe] (IEnumerable`1 source, System.Func`2 predicate, Fallback fallback)

System.Linq.Enumerable.First[Groupe] (IEnumerable`1 source, System.Func`2 predicate)

Assets.ObjetsDeJeu.Goban.GetGroupe (Assets.ObjetsDeJeu.Intersection i) (at Assets/ObjetsDeJeu/Goban.cs:155)
Assets.ObjetsDeJeu.Goban.PutRock (Assets.ObjetsDeJeu.Move m) (at Assets/ObjetsDeJeu/Goban.cs:142)

So the line 142 is

所以142号线是

g.AddRange(GetGroupe(fr)); 

and 155 is

和155是

return this.Groupes.First(g => g.Contains(i));

I don't understand since the this.Groupes is only empty at the very begenning. I did a test where I checked if it was empty before looking for a group but it didn't change anything ...

从这以后我就不明白了。群只在最开始是空的。我做了一个测试，在寻找一个组之前，我检查它是否是空的，但是它没有改变任何东西……

1 个解决方案

#1

The problem is that the call to First() with the specified predicate does not yield any result. Use FirstOrDefault instead and check for null.
Change your code as follows to fix the problem:

问题是，使用指定谓词调用First()不会产生任何结果。使用FirstOrDefault并检查null。更改代码如下，以修复问题:

foreach (Intersection fr in friends)
{
    var group = GetGroupe(fr);
    if(group != null)
       g.AddRange(group);
}
foreach (Intersection fr in friends)
{
   var group = GetGroupe(fr);
   if(group != null)
     this.Groupes.Remove(group);
}


Groupe GetGroupe(Intersection i)
{
   return this.Groupes.FirstOrDefault(g => g.Contains(i));
}