linq 去重复问题

[fengxuemofa6]

return db.product.Where(t => t.p_type == type).Distinct().ToList();这样去除重复数据，没有效果，求教

[EnForGrass]

db.product.Where(t => t.p_type == type).Distinct().ToList();
这样不行？？？

[宝_爸]

product要重载比较的运算符。

[宝_爸]

或者用这个overload:

Enumerable.Distinct<TSource> Method (IEnumerable<TSource>, IEqualityComparer<TSource>)

[宝_爸]

参考这个代码:

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

// Custom comparer for the Product class 
class ProductComparer : IEqualityComparer<Product>
{
    // Products are equal if their names and product numbers are equal. 
    public bool Equals(Product x, Product y)
    {

        //Check whether the compared objects reference the same data. 
        if (Object.ReferenceEquals(x, y)) return true;

        //Check whether any of the compared objects is null. 
        if (Object.ReferenceEquals(x, null) || Object.ReferenceEquals(y, null))
            return false;

        //Check whether the products' properties are equal. 
        return x.Code == y.Code && x.Name == y.Name;
    }

    // If Equals() returns true for a pair of objects  
    // then GetHashCode() must return the same value for these objects. 

    public int GetHashCode(Product product)
    {
        //Check whether the object is null 
        if (Object.ReferenceEquals(product, null)) return 0;

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

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

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

}

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

//Exclude duplicates.

IEnumerable<Product> noduplicates =
    products.Distinct(new ProductComparer());

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

/*
    This code produces the following output:
    apple 9 
    orange 4
    lemon 12
*/

代码来自msdn:
http://msdn.microsoft.com/en-us/library/bb338049

[暖枫无敌]

return db.product.Select(t => t.p_type == type).Distinct().ToList();

[fengxuemofa6]

[Quote=引用 1 楼 的回复:]

return db.product.Select(t => t.p_type == type).Distinct().ToList();
[/Quote]我是个List<model.product>不让用select说是无法吧Bool转换为model.product

[英文字母打字员]

引用 3 楼 Chinajiyong 的回复:

db.product.Where(t => t.p_type == type).Distinct().ToList(); 这样不行？？？

ToList 了 是没有用的 直接VAR接收结果 然后在对象化，实在不可以 手动去除重复项，呵呵

[E次奥]

Distinct里边可以写参数的！