查找清单的值 <object> 使用C＃和linq导致产生真实条件

Question

I have a list of objects which name is ObjectA and another list of Objects that name is ObjectB like:

var result = objectA.any(x=> objectB.contain(x.item));

Now my question is: if my condition was true, how can i find value of ObjectB which caused that made my condition true?

Answer 1

you can try is:

List<ObjectB> sample = new List<ObjectB>();
List<ObjectA> mainList = new List<ObjectA>();
objectB result = sample.FirstOrDefault(ele => mainList.Any(x => ele == x.item);

or If you want Multiple Objects then :-

  List<objectB> resultList = sample.Where(ele => mainList.Any(x => ele == x.item).ToList();

I assumed that ObjectB is a representation of list

Answer 2

A whole plethora of findy routines for your amusement

Enumerable.FirstOrDefault Method (IEnumerable)

Returns the first element of a sequence, or a default value if the sequence contains no elements.

var obj = objectA.FirstOrDefault(x=> objectB.Contains(x.item));

---

Enumerable.First Method (IEnumerable)

Returns the first element of a sequence.

var obj = objectA.First(x=> objectB.Contains(x.item));

---

Enumerable.Where Method (IEnumerable, Func)

Filters a sequence of values based on a predicate. Each element's index is used in the logic of the predicate function.

var objs = objectA.Where(x=> objectB.Contains(x.item));

---

List.IndexOf Method (T)

Searches for the specified object and returns the zero-based index of the first occurrence within the entire List.

var obj = objectA.IndexOf(obj);

---

Enumerable.Last Method (IEnumerable)

Returns the last element of a sequence

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Enumerable.LastOrDefault Method

Returns the last element of a sequence, or a default value if no element is found.

---

Enumerable.Intersect Method (IEnumerable, IEnumerable)

Produces the set intersection of two sequences by using the default equality comparer to compare values.

int[] id1 = { 44, 26, 92, 30, 71, 38 };
int[] id2 = { 39, 59, 83, 47, 26, 4, 30 };

IEnumerable<int> both = id1.Intersect(id2);

foreach (int id in both)
    Console.WriteLine(id);

/*
 This code produces the following output:

 26
 30
*/

---

Enumerable.Except Method (IEnumerable, IEnumerable )

Produces the set difference of two sequences by using the default equality comparer to compare values.

double[] numbers1 = { 2.0, 2.0, 2.1, 2.2, 2.3, 2.3, 2.4, 2.5 };
double[] numbers2 = { 2.2 };

IEnumerable<double> onlyInFirstSet = numbers1.Except(numbers2);

foreach (double number in onlyInFirstSet)
    Console.WriteLine(number);

/*
 This code produces the following output:

 2
 2.1
 2.3
 2.4
 2.5
*/

Answer 3

Be careful with iterating the IEnumerable multiple times.

This is, performance and simplicity wise, a nice approach for you.

var result = objectA.Where(x => objectB.contain(x.item)).ToList();

if (result.Any())
{
    // use the already enumerated objects inside "result" list
}