C#:比较自定义类的两个 ArrayList 并找到重复项 [英] C#: Compare two ArrayList of custom class and find duplicates

问题描述

我有两个 ArrayList 数组.

I have two arrays of ArrayList.

public class ProductDetails
{
    public string id;
    public string description;
    public float rate;
}

ArrayList products1 = new ArrayList();
ArrayList products2 = new ArrayList();
ArrayList duplicateProducts = new ArrayList();

现在我想要的是让所有产品(包含 ProductDetails 类的所有字段)在 products1 和 products2 中都有重复的描述.

Now what I want is to get all the products (with all the fields of ProductDetails class) having duplicate description in both products1 and products2.

我可以像传统方式一样运行两个 for/while 循环，但是如果两个数组中的元素都超过 10k，那将会非常慢.

I can run two for/while loops as traditional way, but that would be very slow specially if I will be having over 10k elements in both arrays.

所以也许可以用 LINQ 做一些事情.

So probably something can be done with LINQ.

推荐答案

如果您想使用 linQ，您需要编写自己的 EqualityComparer，您可以在其中覆盖 Equals 和 GetHashCode()

If you want to use linQ, you need write your own EqualityComparer where you override both methods Equals and GetHashCode()

 public class ProductDetails
    { 
        public string id {get; set;}
        public string description {get; set;}
        public float rate {get; set;}
    }

public class ProductComparer : IEqualityComparer<ProductDetails>
{

    public bool Equals(ProductDetails x, ProductDetails y)
    {
        //Check whether the objects are the same object. 
        if (Object.ReferenceEquals(x, y)) return true;

        //Check whether the products' properties are equal. 
        return x != null && y != null && x.id.Equals(y.id) && x.description.Equals(y.description);
    }

    public int GetHashCode(ProductDetails obj)
    {
        //Get hash code for the description field if it is not null. 
        int hashProductDesc = obj.description == null ? 0 : obj.description.GetHashCode();

        //Get hash code for the idfield. 
        int hashProductId = obj.id.GetHashCode();

        //Calculate the hash code for the product. 
        return hashProductDesc ^ hashProductId ;
    }
}

现在，假设你有这个对象:

Now, supposing you have this objects:

ProductDetails [] items1= { new ProductDetails { description= "aa", id= 9, rating=2.0f }, 
                       new ProductDetails { description= "b", id= 4, rating=2.0f} };

ProductDetails [] items= { new ProductDetails { description= "aa", id= 9, rating=1.0f }, 
                       new ProductDetails { description= "c", id= 12, rating=2.0f } };


IEnumerable<ProductDetails> duplicates =
    items1.Intersect(items2, new ProductComparer());

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