错误的LINQ查询透视

Question

当执行使用LINQ到实体的“键/值表”下面的查询，我得到一个[System.NotSupportedException] "Specified method not supported"：

有人可以给我一个提示我做错了吗？

var Pivot = context.goe_postmeta.GroupBy(pm => pm.post_id).Select(
       g => new PivotTemp 
        { 
         ID = g.Key, 
         FirstName = g.FirstOrDefault(p => p.meta_key == "_billing_first_name").meta_value, 
         LastName = g.FirstOrDefault(p => p.meta_key == "_billing_last_name").meta_value, 
         Address = g.FirstOrDefault(p => p.meta_key == "_billing_address_1").meta_value, 
         PostCode = g.FirstOrDefault(p => p.meta_key == "_billing_postcode").meta_value, 
         Phone = g.FirstOrDefault(p => p.meta_key == "_billing_phone").meta_value, 
         OrderTotal = g.FirstOrDefault(p => p.meta_key == "_order_total").meta_value, 
         PickupLocation = g.FirstOrDefault(p => p.meta_key == "_pickup_location").meta_value, 
         PickupTime = g.FirstOrDefault(p => p.meta_key == "_pickup_time").meta_value, 
         OrderItems = g.FirstOrDefault(p => p.meta_key == "_order_items").meta_value 
        }).ToList(); 

Answer 1

var Pivot = context.goe_postmeta.GroupBy(pm => pm.post_id).Select(
       g => new PivotTemp 
        { 
         ID = g.Key, 
         FirstName = g.FirstOrDefault(p => p.meta_key == "_billing_first_name").meta_value, 
         LastName = g.FirstOrDefault(p => p.meta_key == "_billing_last_name").meta_value, 
         Address = g.FirstOrDefault(p => p.meta_key == "_billing_address_1").meta_value, 
         PostCode = g.FirstOrDefault(p => p.meta_key == "_billing_postcode").meta_value, 
         Phone = g.FirstOrDefault(p => p.meta_key == "_billing_phone").meta_value, 
         OrderTotal = g.FirstOrDefault(p => p.meta_key == "_order_total").meta_value, 
         PickupLocation = g.FirstOrDefault(p => p.meta_key == "_pickup_location").meta_value, 
         PickupTime = g.FirstOrDefault(p => p.meta_key == "_pickup_time").meta_value, 
         OrderItems = g.FirstOrDefault(p => p.meta_key == "_order_items").meta_value 
        }).ToList(); 

也许是因为你缺少的 “” ToList（）之前？只是一个猜测