不能轉換到的System.Guid

Question

我們正在使用實體框架

---

private t_Market getMarketByCellsiteID(Guid cellsiteID) 
{ 
    try 
    { 
     t_Market market = null; 
     using (LiveLeaseEntities Entities = new LiveLeaseEntities()) 
     { 
      market = (from m in Entities.t_Market 
         where m.OperatorId = (from o in Entities.t_CellSite 
              where o.CellSiteId == Guid.Parse("53B7B160-20C4-4B60-948A-06570E6E3CBA") 
              select o.OperatorId) 
         select m).Single(); 
      return market; 
     } 
    } 

---

我得到無法鍵入 'System.Linq.IQueryable' 隱式轉換爲 '的System.Guid'

Answer 1

我想這應該修復它：

private t_Market getMarketByCellsiteID(Guid cellsiteID) 
{ 
try 
{ 
    t_Market market = null; 
    using (LiveLeaseEntities Entities = new LiveLeaseEntities()) 
    { 
     market = (from m in Entities.t_Market 
        where m.OperatorId == (from o in Entities.t_CellSite 
             where o.CellSiteId == Guid.Parse("53B7B160-20C4-4B60-948A-06570E6E3CBA") 
             select o.OperatorId).Single() 
        select m).Single(); 
     return market; 
    } 
} 

兩件事情：你需要一個==做比較m.OperatorId，和你將它與一個返回IQuerable的LINQ查詢進行比較 - 在​​LINQ查詢中調用Single（）執行該查詢並返回一個值進行比較。

Answer 2

您的問題與此比較：

m.OperatorId = (from o in Entities.t_CellSite 
    where o.CellSiteId == Guid.Parse("53B7B160-20C4-4B60-948A-06570E6E3CBA") 
    select o.OperatorId) 

您正在比較System.Guid和System.Linq.IQueryable<System.Guid>。如果您希望只有一個結果，你可以這樣做：

m.OperatorId = (from o in Entities.t_CellSite 
    where o.CellSiteId == Guid.Parse("53B7B160-20C4-4B60-948A-06570E6E3CBA") 
    select o.OperatorId).First()