C# 比較兩個列表，返回列表中的新項目

Question

我有 2 個對象列表。 我想比較它們並返回新列表中的所有新對象

我嘗試下面的代碼，但我沒有得到答復

 var inInsyt = (from prd in db.COM_CUSTOMER_PRODUCT
                 join inv in db.INS_INVENTORY on prd.COM_CUSTOMER_PRODUCT_ID 
                 equals inv.COM_PRODUCT_ID
                 where prd.COM_CUSTOMER_ID == 5252
                 select new ProductInventoryInfo
                 {
                     sku = prd.PRODUCT_CODE,
                     quantity = inv.INV_AVAILABLE
                 }).ToList();


            var inEComSite = (from qlInv in db.INS_OPENCART_QOOLMART_INVENTORY
                              where qlInv.ID>0
                              select new ProductInventoryInfo
                              {
                                  sku = qlInv.SKU,
                                  quantity = qlInv.QUANTITY
                              }).ToList();

--------第一種方法------------------------------------ ------------------------------------

            var firstNotSecond = inInsyt.Except(inEComSite).ToList();
            var secondNotFirst = inEComSite.Except(inInsyt).ToList();

------------------第二種方法---------------------------- ------------------------------

 List<ProductInventoryInfo> objectList3 = inEComSite.Where(o => inInsyt.Contains(o)).ToList();

 List<ProductInventoryInfo> objectList4 = inInsyt.Where(o => !inEComSite.Contains(o)).ToList();

---

Answer 1

您應該為ProductInventoryInfo類實現一個IEqualityComparer 。

看看這里

Answer 2

如果你有兩個字符串或數字列表，你可以使用下面的方法來比較

主要方法

var list1 = new List<string>
        {
            "Product 1",
            "Product 2",
            "Product 3",
            "Product 4"
        };

var list2 = new List<string>
        {
            "Product 2",
        };

var list3 = list1.Where(i => list2.All(x => x != i)).ToList();

var list4 = list1.Except(list2).ToList();

如果兩個列表是對象，您可以使用以下方法進行比較

類ProductInventoryInfo

public class ProductInventoryInfo
{
    public string ProductName { get; set; }

    public override bool Equals(object obj)
    {
        if (!(obj is ProductInventoryInfo))
        {
            return false;
        }

        var other = (ProductInventoryInfo)obj;
        return this.ProductName == other.ProductName;
    }

    protected bool Equals(ProductInventoryInfo other)
    {
        return ProductName == other.ProductName;
    }

    public override int GetHashCode()
    {
        return (ProductName != null ? ProductName.GetHashCode() : 0);
    }
}

比較對象的擴展方法

public static class ExtensionsMethod
{
    public static bool ObjectsAreEqual(this IEnumerable<ProductInventoryInfo> items, ProductInventoryInfo obj2)
    {
        return items.Any(productInventoryInfo => ObjectsAreEqual<ProductInventoryInfo>(productInventoryInfo, obj2));
    }

    private static bool ObjectsAreEqual<T>(T obj1, T obj2)
    {
        return JsonConvert.SerializeObject(obj1) == JsonConvert.SerializeObject(obj2);//convert object to json by Newtonsoft.Json and compare that
    }
}

主要方法

 var list1 = new List<ProductInventoryInfo>
        {
            new ProductInventoryInfo{ ProductName="Product 1"},
            new ProductInventoryInfo{ ProductName="Product 2"},
            new ProductInventoryInfo{ ProductName="Product 3"},
            new ProductInventoryInfo{ ProductName="Product 4"},
        };

 var list2 = new List<ProductInventoryInfo>
        {
            new ProductInventoryInfo{ ProductName="Product 2"},
        };

 var list3 = list1.Where(x => !list2.ObjectsAreEqual(x)).ToList(); //use Extensions Method

 //use override Equals
 var list4 = new List<ProductInventoryInfo>();

 list1.ForEach(x =>
     {
       list2.ForEach(y =>
          { 
            if (!x.Equals(y))
              {
                 list4.Add(x);
              }
          });
      });

Answer 3

請參閱以下代碼段：

        List<int> firstList = new List<int>() { 1,2,2,3,3 };
        List<int> secondList = new List<int>() { 1 };
        List<int> newList = new List<int>();

        var firstNotSecond = firstList.Except(secondList).ToList();
        var secondNotFirst = secondList.Except(firstList).ToList();

        newList.AddRange(firstNotSecond);
        newList.AddRange(secondNotFirst);

輸出新列表：{2,3}

Answer 4

如果您將對象添加到相同類型的列表中，這將非常有效

var differences = list2.Where(l2 => 
    !list1.Any(l1 => l1.sku == l2.sku && l1.quantity == l2.quantity ));

或者（如果你願意）

 var differences = list2.Where(l2 => 
        !list1.Any(l1 => l1.sku == l2.sku || l1.quantity == l2.quantity ));