检索出 IList<T> 或 List<T>中的不重复数据 Distinct()

http://www.soaspx.com/dotnet/csharp/csharp_20130513_10318.html

Distinct()方法在MSDN中的示例

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

Product[] products = { new Product { Name = "apple", Code = 9 }, 
                       new Product { Name = "orange", Code = 4 }, 
                       new Product { Name = "apple", Code = 10 }, 
                       new Product { Name = "lemon", Code = 9 } };
var lstDistProduct = products.Distinct();
foreach (Product p in list1)
{
     Console.WriteLine(p.Code + " : " + p.Name);
}

但在实际使用中发现往往无法实现筛选出不重复的数据的目的

查找相关资料获得如下方法：

方法1：使用MoreLinq库

var list1 = products.DistinctBy(x=> x.Code);




foreach (Product p in list1)
{
     Console.WriteLine(p.Code + " : " + p.Name);
}

方法2：

class ProductComparare : IEqualityComparer<product>
    {
        private Func<Product, object> _funcDistinct;
        public ProductComparare(Func<Product, object> funcDistinct)
        {
            this._funcDistinct = funcDistinct;
        }




        public bool Equals(Product x, Product y)
        {
            return _funcDistinct(x).Equals(_funcDistinct(y));
        }




        public int GetHashCode(Product obj)
        {
            return this._funcDistinct(obj).GetHashCode();
        }
    }

var list2 = products.Distinct(new ProductComparare( a => a.Code ));




            foreach (Product p in list2)
            {
                Console.WriteLine(p.Code + " : " + p.Name);
            }

方法3：

 List<Product> list = products
                   .GroupBy(a => a.Code )
                   .Select(g => g.First())
                   .ToList();




            foreach (Product p in list)
            {
                Console.WriteLine(p.Code + " : " + p.Name);
            }

本人通过第三种方法得到了想要的不重复数据。