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  • LINQ中的group操作

    static void Main(string[] args)
    {
        var products=new[]
            {
                new{ProductName="Apple",Category="Food"},
                new{ProductName="Cat",Category="Animal"},
                new{ProductName="Dog",Category="Other"},
                new{ProductName="Pig",Category="Animal"},
            };

        var q = from p in products
                group p by p.Category into g
                orderby g.Key
                select g;

        foreach (var item in q)
        {
            Console.WriteLine(item.Key);
            foreach (var i in item)
            {
                Console.WriteLine("\t" + i.ProductName);
            }
        }

        Console.Read();

    }

    image

    另外一个结合join的例子

    static void Main(string[] args)
    {
        NorthwindDataContext db = new NorthwindDataContext();
        var products = db.Products;
        var categorys = db.Categories;

        var query = from result in
                        from p in products.AsEnumerable()
                        join c in categorys.AsEnumerable()
                        on p.CategoryID equals c.CategoryID //这里必须写equals,而不能是=
                        select new { CategoryName = c.CategoryName, Product = p }
                    group result by result.CategoryName into g
                    select g;

        foreach (var group in query)
        {
            Console.WriteLine(group.Key);
            foreach (var product in group)
            {
                Console.WriteLine("\t"+product.Product.ProductName);
            }
        }
        Console.Read();

    }

     

    image

    【注意】我这里用的是LINQ TO SQL模型,访问了Northwind这个数据库

    image

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  • 原文地址:https://www.cnblogs.com/chenxizhang/p/1488100.html
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