Select multiple columns using Entity Framework

Question

Maybe an easy question  but can t find it easily so forgive me    I try to select multiple columns  The statement I use is   var dataset2   from recordset in entities processlists                 where recordset ProcessName    processname                 select recordset ServerName  recordset ProcessID  recordset Username    Obviously  this doesn t even compile  What is the correct syntax  I also tried method based  and even tough this syntax seems correct  when accessing it throws an  Unable to cast the type  Anonymous type  to type  AIM PInfo   LINQ to Entities only supports casting EDM primitive or enumeration types   exception   Any ideas   var dataset   entities processlists               Where x   gt  x environmentID    environmentid  amp  amp  x ProcessName    processname  amp  amp  x RemoteIP    remoteip  amp  amp  x CommandLine    commandlinepart                Select x   gt  new   x ServerName  x ProcessID  x Username                  Cast lt PInfo gt    ToList

User · Answer

Here is a code sample    var dataset   entities processlists      Where x   gt  x environmentID    environmentid  amp  amp  x ProcessName    processname  amp  amp  x RemoteIP    remoteip  amp  amp  x CommandLine    commandlinepart       Select x   gt  new PInfo                                            ServerName   x ServerName                         ProcessID   x ProcessID                         UserName   x Username                      AsEnumerable                   Select y   gt  new PInfo                                     ServerName   y ServerName                     ProcessID   y ProcessID                     UserName   y UserName                    ToList

User · Answer

Why don t you create a new object right in the  Select    Select x   gt  new PInfo       ServerName   x ServerName       ProcessID   x ProcessID       UserName   x Username    ToList

User · Answer

var test obj   from d in repository DbPricing join d1 in repository DbOfficeProducts on d OfficeProductId equals d1 Id join d2 in repository DbOfficeProductDetails on d1 ProductDetailsId equals d2 Id     select new           PricingId   d Id      LetterColor   d2 LetterColor      LetterPaperWeight   d2 LetterPaperWeight          http   www cybertechquestions com select-across-multiple-tables-in-entity-framework-resulting-in-a-generic-iqueryable 222801 html

User · Answer

You can select to an anonymous type  for example  var dataset2         from recordset in entities processlists      where recordset ProcessName    processname      select new               serverName   recordset ServerName          processId   recordset ProcessID           username   recordset Username        ToList      Or you can create a new class that will represent your selection  for example  public class MyDataSet       public string ServerName   get  set        public string ProcessId   get  set        public string Username   get  set        then you can for example do the following   var dataset2         from recordset in entities processlists      where recordset ProcessName    processname      select new MyDataSet               ServerName   recordset ServerName          ProcessId   recordset ProcessID           Username   recordset Username        ToList

User · Answer

You either want to select an anonymous type   var dataset2   from recordset                 in entities processlists                 where recordset ProcessName    processname                 select new                                   recordset ServerName                   recordset ProcessID                   recordset Username                     But you cannot cast that to another type  so I guess you want something like this   var dataset2   from recordset                 in entities processlists                 where recordset ProcessName    processname                     Select new concrete type                select new PInfo                                  ServerName   recordset ServerName                   ProcessID   recordset ProcessID                   Username   recordset Username

User · Answer

Indeed  the compiler doesn t know how to convert this anonymous type  the new   x ServerName  x ProcessID  x Username   part  to a PInfo object   var dataset   entities processlists      Where x   gt  x environmentID    environmentid  amp  amp  x ProcessName    processname  amp  amp  x RemoteIP    remoteip  amp  amp  x CommandLine    commandlinepart       Select x   gt  new   x ServerName  x ProcessID  x Username    ToList      This gives you a list of objects  of anonymous type  you can use afterwards  but you can t return that or pass that to another method   If your PInfo object has the right properties  it can be like this    var dataset   entities processlists      Where x   gt  x environmentID    environmentid  amp  amp  x ProcessName    processname  amp  amp  x RemoteIP    remoteip  amp  amp  x CommandLine    commandlinepart       Select x   gt  new PInfo                                            ServerName   x ServerName                         ProcessID   x ProcessID                         UserName   x Username                      ToList      Assuming that PInfo has at least those three properties   Both query allow you to fetch only the wanted columns  but using an existing type  like in the second query  allows you to send this data to other parts of your app

User · Answer

It s correct way to get data in specified type   var dataset   entities processlists           Where x   gt  x environmentID    environmentid  amp  amp  x ProcessName    processname  amp  amp  x RemoteIP    remoteip  amp  amp  x CommandLine    commandlinepart            Select x   gt  new   x ServerName  x ProcessID  x Username              ToList       To get data from database           Select x   gt  new PInfo                                       ServerName   x ServerName                      ProcessID   x ProcessID                      Username   x Username                      For more information see  The entity cannot be constructed in a LINQ to Entities query

[c#] Select multiple columns using Entity Framework

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