Best way to check if an object exists in the Entity Framework?

Question

What is the best way to check if an object exists in the database in terms of performance? I am using Entity Framework 1.0 (ASP.NET 3.5 SP1).

Answer 1

If you do not 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 it may be necessary to check each line before returning.

Here is an example of how to use it:

if (context.MyEntity.Any(o => o.Id == idToMatch)) { // Match! } 

And in vb.net

 If context.MyEntity.Any(function(o) o.Id = idToMatch) Then ' Match! End If 

Answer 2

In terms of performance, I assume that direct SQL querying with the EXISTS command would be appropriate. See here how to execute SQL directly in the Entity Framework: http://blogs.microsoft.co.il/blogs/gilf/archive/2009/11/25/execute-t-sql-statements-in-entity-framework- 4.aspx

Answer 3

I know this is a very old thread, but just so that someone like me needs this solution, but in VB.NET, here I used the base for 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 

Answer 4

I had some problems with this - my EntityKey has three properties (PK with 3 columns), and I did not want to check each of the columns because it would be ugly. I was thinking of a solution that works all the time with all entities.

Another reason for this is that I do not like to infect UpdateExceptions every time.

A little Reflection is required to get the key property values.

The code is implemented as an extension that simplifies the use of:

 context.EntityExists<MyEntityType>(item); 

Take a look:

 public static bool EntityExists<T>(this ObjectContext context, T entity) where T : EntityObject { object value; var entityKeyValues = new List<KeyValuePair<string, object>>(); var objectSet = context.CreateObjectSet<T>().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<string, object>(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; } 

Answer 5

I had to manage a scenario in which the percentage of duplicates that was provided in the new data records was very high, and so many thousands of database calls were made to check for duplicates (therefore, the CPU sent a lot of time 100%). In the end, I decided to keep the last 100,000 entries in the cache in memory. That way, I could check for duplicates in cached records that were extremely fast compared to LINQ query with SQL database, and then write any really new records to the database (and also add them to the data cache, which is also sorted and trimmed to maintain its length).

Note that the raw data was a CSV file that contained many individual records that needed to be analyzed. The entries in each sequential file (which arrived at a rate of about 1 time in 5 minutes) overlapped significantly, hence a high percentage of duplicates.

In short, if you have timestamped raw data that is pretty much ordered, then using a memory cache can help with checking for duplicate entries.

Answer 6

I just check if the 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"; } 

Answer 7

Why not do it?

 var result= ctx.table.Where(x => x.UserName == "Value").FirstOrDefault(); if(result.field == value) { // Match! }