Question

我试图比较两个包含复杂对象的c＃列表。我知道之前已经提出了类似的问题，但这有点不同。我按照MSDN示例写了这封信：https://msdn.microsoft.com/en-us/library/bb300779(v=vs.110).aspx

public class ProductA
{ 
    public string Name { get; set; }
    public int Code { get; set; }
}

public class ProductComparer : IEqualityComparer<ProductA>
{

    public bool Equals(ProductA x, ProductA 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.Code.Equals(y.Code) && x.Name.Equals(y.Name);
    }

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

        //Get hash code for the Code field. 
        int hashProductCode = obj.Code.GetHashCode();

        //Calculate the hash code for the product. 
        return hashProductName ^ hashProductCode;
    }
}

然后使用Except方法删除＆＃34; apple＆＃34;列表中的9

ProductA[] fruits1 = { new ProductA { Name = "apple", Code = 9 }, 
                       new ProductA { Name = "orange", Code = 4 },
                        new ProductA { Name = "lemon", Code = 12 } };

ProductA[] fruits2 = { new ProductA { Name = "apple", Code = 9 } };

//Get all the elements from the first array //except for the elements from the second array. 
IEnumerable<ProductA> except = fruits1.Except(fruits2);

foreach (var product in except)
    Console.WriteLine(product.Name + " " + product.Code);

此代码应生成以下输出：橙子4柠檬12

我没有并打印出以下内容：苹果9橙4柠檬12

Answer 1

MSDN文档中似乎出现错误：https://msdn.microsoft.com/en-us/library/bb300779(v=vs.110).aspx

Except方法调用应该使用IEqualityComparer：

//Get all the elements from the first array //except for the elements from the second array. 
ProductComparer pc = new ProductComparer();
IEnumerable<ProductA> except = fruits1.Except(fruits2, pc);

使用IEqualityComparer来比较两个列表

1 个答案: