帶有多個連接結果的LINQ查詢，用逗號分隔結果

Question

以下查詢返回連接到「地址」表的導線列表，其中每個導聯可以有多個導聯。

我期待每個潛在客戶返回一個響應，地址在模型內城市視圖中連接並用逗號分隔。如果連接結果中沒有城市，則應返回' - '。

電流輸出

Company Name | Company City 
=========================== 
Company 1 | Glasgow 
Company 1 | London 
Company 2 | London 
Company 3 | NULL 

所需的輸出

=========================== 
Company 1 | Glasgow, London 
Company 2 | London 
Company 3 | - 

QUERY

return (from t1 in db.Opportunities 
        from s1 in db.OpportunityStatus.Where(x => x.OpportunityStatus_ID == t1.StatusReason_ID) 
        from t2 in db.Leads.Where(x => x.Lead_ID == t1.Lead_ID) 
        from t3 in db.LeadAddresses.Where(x => x.Lead_ID == t2.Lead_ID).DefaultIfEmpty() 
        from t4 in db.Addresses.Where(x => x.Address_ID == t3.Address_ID).DefaultIfEmpty() 
        orderby (t1.Created) descending 
        select new FieldSalesPipelineViewModel 
        { 
         Id = t1.Opportunity_ID, 
         CompanyName = t2.Company_Name, 
         OpportunityTitle = t1.Opportunity_Title, 
         CompanyCity = "", 
         OpportunityStatusName = s1.OpportunityStatus_Name 
        }).Take(howMany); 

Answer 1

嘗試使用字符串連接：

CompanyCity = string.Join(",", (from p in db.Opportunities where t2.companyname == p.companyname select p.Companycity) 

對於示例：

return (from t1 in db.Opportunities 
        from s1 in db.OpportunityStatus.Where(x => x.OpportunityStatus_ID == t1.StatusReason_ID) 
        from t2 in db.Leads.Where(x => x.Lead_ID == t1.Lead_ID) 
        from t3 in db.LeadAddresses.Where(x => x.Lead_ID == t2.Lead_ID).DefaultIfEmpty() 

        orderby (t1.Created) descending 
        select new FieldSalesPipelineViewModel 
        { 
         Id = t1.Opportunity_ID, 
         CompanyName = t2.Company_Name, 
         OpportunityTitle = t1.Opportunity_Title, 
         CompanyCity = string.Join(",", (from t4 in db.Addresses Where t4.Address_ID == t3.Address_ID select t4.CompanyCity), 
         OpportunityStatusName = s1.OpportunityStatus_Name 
        }).Take(howMany);