Best way to check if object exists in Entity Framework

Question

What is the best way to check if an object exists in the database from a performance point of view  I m using Entity Framework 1 0  ASP NET 3 5 SP1

User · Answer

Best way to do it Regardless of what your object is and for what table in the database the only thing you need to have is the primary key in the object  C  Code var dbValue   EntityObject Entry obj  GetDatabaseValues    if  dbValue    null       Don t exist    VB NET Code Dim dbValue   EntityObject Entry obj  GetDatabaseValues   If dbValue Is Nothing Then    Don t exist End If

User · Answer

I just check if object is null   it works 100  for me      try               var ID   Convert ToInt32 Request Params  ID             var Cert    from cert in db TblCompCertUploads where cert CertID    ID select cert  FirstOrDefault            if  Cert    null                        db TblCompCertUploads DeleteObject Cert               db SaveChanges                ViewBag Msg    Deleted Successfully                     else                       ViewBag Msg    Not Found                                                     catch               ViewBag Msg    Something Went wrong

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I know this is a very old thread but just incase someone like myself needs this solution but in VB NET here s what I used base on the answers above   Private Function ValidateUniquePayroll PropertyToCheck As String  As Boolean        Return true if Username is Unique     Dim rtnValue   False     Dim context   New CPMModel CPMEntities     If  context Employees Any    Then   Check if there are  any  records in the Employee table         Dim employee   From c In context Employees Select c PayrollNumber   Select just the PayrollNumber column to work with         For Each item As Object In employee   Loop through each employee in the Employees entity             If  item   PropertyToCheck  Then   Check if PayrollNumber in current row matches PropertyToCheck                    Found a match  throw exception and return False                 rtnValue   False                 Exit For             Else                    No matches  return True  Unique                  rtnValue   True             End If         Next     Else            The is currently no employees in the person entity so return True  Unqiue          rtnValue   True     End If     Return rtnValue End Function

User · Answer

Why not do it   var result  ctx table Where x   gt  x UserName     Value   FirstOrDefault     if result  field    value         Match

User · Answer

I had some trouble with this - my EntityKey consists of three properties  PK with 3 columns  and I didn t want to check each of the columns because that would be ugly  I thought about a solution that works all time with all entities   Another reason for this is I don t like to catch UpdateExceptions every time   A little bit of Reflection is needed to get the values of the key properties   The code is implemented as an extension to simplify the usage as    context EntityExists lt MyEntityType gt  item     Have a look   public static bool EntityExists lt T gt  this ObjectContext context  T entity          where T   EntityObject               object value          var entityKeyValues   new List lt KeyValuePair lt string  object gt  gt             var objectSet   context CreateObjectSet lt T gt    EntitySet          foreach  var member in objectSet ElementType KeyMembers                        var info   entity GetType   GetProperty member Name               var tempValue   info GetValue entity  null               var pair   new KeyValuePair lt string  object gt  member Name  tempValue               entityKeyValues Add pair                     var key   new EntityKey objectSet EntityContainer Name         objectSet Name  entityKeyValues           if  context TryGetObjectByKey key  out value                         return value    null                    return false

User · Answer

If you don t want to execute SQL directly  the best way is to use Any    This is because Any   will return as soon as it finds a match  Another option is Count    but this might need to check every row before returning   Here s an example of how to use it   if  context MyEntity Any o   gt  o Id    idToMatch            Match      And in vb net  If context MyEntity Any function o  o Id   idToMatch  Then       Match  End If

User · Answer

I had to manage a scenario where the percentage of duplicates being provided in the new data records was very high  and so many thousands of database calls were being made to check for duplicates  so the CPU sent a lot of time at 100     In the end I decided to keep the last 100 000 records cached in memory   This way I could check for duplicates against the cached records which was extremely fast when compared to a LINQ query against the SQL database  and then write any genuinely new records to the database  as well as add them to the data cache  which I also sorted and trimmed to keep its length manageable    Note that the raw data was a CSV file that contained many individual records that had to be parsed   The records in each consecutive file  which came at a rate of about 1 every 5 minutes  overlapped considerably  hence the high percentage of duplicates   In short  if you have timestamped raw data coming in  pretty much in order  then using a memory cache might help with the record duplication check

User · Answer

From a performance point of view  I guess that a direct SQL query using the EXISTS command would be appropriate  See here for how to execute SQL directly in Entity Framework  http   blogs microsoft co il blogs gilf archive 2009 11 25 execute-t-sql-statements-in-entity-framework-4 aspx

[entity-framework] Best way to check if object exists in Entity Framework?

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