在匿名类型上编写 Group By

Question

我正在两个表上编写一个 group by 子句，这两个表已连接并通过实体数据模型进行访问。我无法迭代匿名类型，有人可以帮助我吗？

 public string GetProductNameByProductId(int productId)
    {
        string prodName=string.Empty;        
        using (VODConnection vodObjectContext = new VODConnection())
        {

            var products = from bp in vodObjectContext.BFProducts
                                             join bpf in vodObjectContext.BFProductMasters on bp.ProductMasterId equals bpf.ProductMasterId
                                             where bp.ProductId == productId
                           group bp by new { ProductId = bp.ProductId, ProductName = bp.ProductName, ProductMasterName=bpf.ProductMasterName} into newInfo
                           select newInfo;

//Want to iterate over products or in fact need to get all the results. How can I do that? Want productmastername property to be set in prodName variable by iterating

            return (prodName);
        }
    }

Answer 1

一个问题是您无缘无故地使用了查询延续。请注意，这仍然不应该阻止您使用 Key 属性。尝试使用一种稍微简洁的方法：

var products = from bp in vodObjectContext.BFProducts
               join bpf in vodObjectContext.BFProductMasters
                 on bp.ProductMasterId equals bpf.ProductMasterId
               where bp.ProductId == productId
               group bp by new { bp.ProductId,
                                 bp.ProductName, 
                                 bpf.ProductMasterName};

foreach (var group in products)
{
    var key = group.Key;
    // Can now use key.ProductName, key.ProductMasterName etc.
}

至于将 prodName 变量设置为什么 - 目前还不清楚您到底想要什么。第一个 ProductName 值？最后一个？所有这些的串联？为什么需要分组？

Answer 2

foreach(var prod in products)
{
  prodName += prod.Key.ProductMasterName;
}