搜索自定义类列表的属性

Question

I have a custom class called CustomClass. It contains a variable called "Name" and a list of values (for the sake of simplicity let's make this an int - in reality it is another custom class, but the principle should be the same).

So :

public class CustomClass {
   string name;


} 

I have a List<CustomClass> .

When I attempt to add a value to this List, the logic I want, is for this List to check if it contains a CustomClass with the same name as the value I want to add.

If it does, then do x, otherwise, do y.

listOfCustomClass.Contains(customClassToAdd.name) will not work in this case, I assume, however this is the functionality I require.

What is best practice here ?

Answer 1

我认为您可以尝试类似var x = MyList.Where（C => C.Name == InsertedName）的方法并检查结果（未经测试）

Answer 2

You'll have to create a new class,let's call it CustomList, that inherits from IList<> where you can override the add method, do your check, and then add it to the base. Something like this:

public class CustomList<T> : IList<T> where T : CustomClass
{
    private List<T> innerlist;
    public void Add(T item)
    {
        if(innerlist.Any(a => a.Name == item.Name)))
            innerlist.Add(item);
    }
}

Answer 3

you can do it using linq as follow but you have to make name field public.

        List<CustomClass> list = new List<CustomClass>();
        CustomClass toCheck = new CustomClass();

        if (list.Any(p => p.name.Equals(toCheck)))
        {
            //do x here
        }
        else
        {
            //do y here
        }

however if you don't want to use linq then Do some changes in CustomClass as follow

public class CustomClass
{
    string name;
    List<int> intLost = new List<int>();

    public override bool Equals(object obj)
    {
        return this.Equals(obj as CustomClass);
    }

    public override int GetHashCode()
    {
        return 0;
    }

    public bool Equals(CustomClass cc)
    {
        if (cc == null) return false;
        return this.name.Equals(cc.name);
    }
}

Then you can do this.

        List<CustomClass> list = new List<CustomClass>();

        CustomClass toCheck = new CustomClass();
        if (list.Contains(toCheck))
        {
            //do x here
        }
        else
        {
            //do y here
        }

Answer 4

It seems to me that you want to override the .Add() behavior of your List<CustomClass>. While you could use extension methods, I think a better solution would be to invent a class that extends List in some manner. I'd recommend implementing IList in your collection class if you need to have that level of control over add operations...

    public class CustomClassList : IList<CustomClass>
    {
        public void Add (CustomClass item)
        {
            if(this.Select(t => t.Name).Contains(item.Name))
                // Do whatever here...
            else
                // Do whatever else here...
        }

        // ... other IList implementations here ...
    }

Answer 5

try this:

IList<CustomClass> list = new List<CustomClass>();

CustomClass customClass = new CustomClass();
customClass.name = "Lucas";

if((list.Tolist().Find(x => x.name == customClass.name)) == null)
{
    list.Add(customClass);
}
else
{
    //do y;
}

Answer 6

You could override the Equals(object o) function in your CustomClass, so that two CustomClasses are considered equal if their names are the same. Then

listOfCustomClass.Contains(customClassToAdd);

should work.

Answer 7

另一种方法是在CustomClass上重写Equals方法，然后仅调用List.Contains（）

Answer 8

If the name property uniquely identifies the CustomClass, then you should overload Equals and GetHashCode() . The reason List.Contains doesn't work is that underneath the HashCodes are compared. So you need to overload GetHashCode and Equals something like this:

public override int GetHashCode()
{
    return this.name.GetHashCode();
}

public override bool Equals(object obj)
{
    var other = obj as CustomClass;

    if (other != null)
    {
        if (other.Name == this.Name)
        {
             return true;
        }
    }
    return false;
}