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这是我的 Linq 查询。这工作正常。问题是如果任何人在表中没有姓氏，则该行不会显示在结果中。我希望如果有人没有姓氏，那么它将是 User_Name= First Name +""。

var ShowFiles = from cm in db.Contact_Masters
                        join ta in db.Topic_Accesses on cm.Contact_ID equals ta.Contact_ID
                        join RelMess in db.Rel_Topics_Messages on ta.Topic_ID equals RelMess.Topic_ID
                        join Messages in db.Messages on RelMess.Message_ID equals Messages.Message_ID
                        join Files in db.Files on Messages.Message_ID equals Files.Message_ID
                        join FileType in db.Lkup_Files_Extensions on Files.TypeID equals FileType.TypeID
                        join FileVersion in db.File_Versions on Files.File_ID equals FileVersion.File_ID
                        join pcf in db.Contact_Personals on Messages.Contact_ID equals pcf.Contact_ID
                        where pcf.Personal_Type == new Guid("30102333-2104-40D7-8913-DC9048225D12") // Personal_Type = First Name ID
                        join pcl in db.Contact_Personals on Messages.Contact_ID equals pcl.Contact_ID
                        where pcl.Personal_Type == new Guid("9058F268-B707-4B0A-86E5-26E83A4BC1F5") // Personal_Type = Last Name ID 

                        where cm.Contact_ID == new Guid(ContactID) && ids.Contains(RelMess.Topic_ID)// parameters
                        && FileVersion.IsActive == true && Messages.IsActive == true && FileVersion.Version_ID == (from FileV in db.File_Versions
                                                                                                                   where FileV.File_ID == Files.File_ID 
                                                                                                                   && FileV.Message_ID == Messages.Message_ID 
                                                                                                                   && FileV.IsActive == true
                                                                                                                   select FileV.Version_ID).Max()
                        select new
                        {
                            File_Name = Convert.ToString(Files.File_Name),
                            Version_ID = Convert.ToString(FileVersion.Version_ID),
                            File_Size = Convert.ToString(FileVersion.File_Size),
                            Created = Convert.ToString(FileVersion.Created),
                            Type = FileType.Type,
                            File_URL = FileVersion.File_URL,
                            File_ID = Convert.ToString(FileVersion.File_ID),
                            User_Name = pcf.Value + " " + pcl.Value  
                        };

谢谢纳希德
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1 回答 1

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尝试以下操作：

User_Name = pcf.Value + 
    (pcf.Value != null && pcf.Value.Trim() != string.Empty ? " " + pcl.Value : "")

编辑：删除了 IsNullOrWhiteSpace 的使用，感谢 Jacek

于 2012-04-05T10:17:13.197 回答