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Better way to update/insert values using EF

I am trying to solve a problem as well as learn and improve my code skills here.
I am using Entity Framework and am tasked with writing to a SQL table, where I can update or insert based on whether a row exists or not. If it doesn't exist then add it, if it does exist then update it if required.
I have 2 lists, the first list is the EF type from the table that I am writing to. The second list is a class which is made up from a SQL query but shares some of the columns from the table which needs updating, thus if they differ then update the table with the differing property values.
foreach (var tbl in Table_List)
{
foreach (var query in SQL_Query)
{
if (tbl.ID == query.ID)
{
bool changed = false;
if (tbl.Prop1 != query.Prop1)
{
tbl.Prop1 = query.Prop1;
changed = true;
}
if (tbl.Prop2 != query.Prop2)
{
tbl.Prop2 = query.Prop2;
changed = true;
}
if (changed)
await Context.SaveChangesAsync();
}
}
}
There are 10 properties in total in the class, but even if all 10 of them differ I only have to update 2 properties, the rest can stay the same. So to summarize, my question is;
Is there a better way to update these 2 properties? Something other than a bulky series of if statements and foreach loops? Any info on straight up inserting would be appreciated too, thanks very much!

EF uses an internal ChangeTracker. This means that when you change a property of an entity that is being tracked (you queried the lists using a DbSet on the Context) it will marked as "Changed" in the ChangeTracker. This is used by the SaveChangesAsync to determine what to do, ie. insert of update and what fields need to be updated.
Second, this ChangeTracker is smart enough to detect that when you set a property to the same value it already has it won't be marked as a Change.
Also with this ChangeTracker there is no need to call SaveChangesAsync after every change. You can call it at the end of the loop.
foreach (var tbl in Table_List)
{
foreach (var query in SQL_Query)
{
if (tbl.ID == query.ID)
{
tbl.Prop1 = query.Prop1;
tbl.Prop2 = query.Prop2;
}
}
}
await Context.SaveChangesAsync();

How do I get an identity value with Entity Framework(v5) before I save the record

I am new to entity framework and I have been searching a while for an answer to this question and I can't find anything that directally addresses this.
Here is the problem. I have a table in Oracle. In this table there are 2 fields(there are more but not important to this question). Card_Transaction_Id and Parent_Card_Transaction_ID. The Parent_Card_Transaction_Id field is constrained by the Card_Transaction_Id field and I am using a Oracle sequence via a trigger to populate the Card_Transaction_Id field.
In my code, I am using Entity Framework(Version 5) to connect using the Code First Approach.
The issue is when I try to create a new record. I need to know what the next sequence value is in order to populate the Parent_Card_Transaction_Id. My mapping for card transactions:
public class CardTransactionMap : EntityTypeConfiguration<CardTransaction>
{
public CardTransactionMap(string schema)
{
ToTable("CARD_TRANSACTION", schema);
// Mappings & Properties
// Primary Key
HasKey(t => t.CardTransactionId);
Property(t => t.CardTransactionId)
.HasColumnName("CARD_TRANSACTION_ID")
.HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity);
Property(t => t.ParentCardTransactionId)
.HasColumnName("PARENT_CARD_TRANSACTION_ID");
Property(t => t.CardProfileId)
.HasColumnName("CARD_PROFILE_ID");
}
}
The question is - is there any way to get the next sequence number before I save the record?
My current work arround is to use the following method:
public static decimal GetNextCardTransactionSequenceValue()
{
using (var context = new Context(new OracleConnectionFactory().GetConnection()))
{
var sequence = context.Database.SqlQuery<int>("select card_transaction_id from card_transaction").ToList();
return sequence[0];
}
}
Using that method, I get the next value and then just populate my table. This works but I don't like doing it this way. I feel that there must be a better way to do it.
Thanks in advance.

You have to do this by navigation properties.
By fetching the next value from a sequence before actually using it in the same session you create yourself a concurrency issue: another user can increment the index (by an insert) in the time between drawing its next value and assigning it to the child record. Now the child will belong to the other user's record!
If your CardTransaction class has a parent reference like this:
int ParentCardTransaction { get; set; }
[ForeignKey("ParentCardTransaction")]
CardTransaction ParentCardTransaction { get; set; }
you can create a parent and child in one go and call SaveChanges without worrying about setting FK values yourself:
var parent = new CardTransaction { ... };
var child = new CardTransaction { ParentCardTransaction = parent, ... };
SaveChanges();
Now EF wil fetch the new CardTransactionId from the parent and assign it to the FK of the child. So generating and getting the parent Id happens all in one session, so it is guaranteed to be the same value.
Apart from preventing concurrency issues, of course it is much easier anyway to let EF do the heavy lifting of getting and assiging key values.

Create a Stored Procedure or Query that will return you the next Value from the Table here is an Example
SELECT NVL(MAX(card_transaction_id + 1), 0) AS MAX_VAL
FROM card_transaction T;
or Create a Trigger - for OracleDB

Change your table definition to this :
CREATE TABLE t1 (c1 NUMBER GENERATED BY DEFAULT ON NULL AS IDENTITY,
c2 VARCHAR2(10));
as per the information in the link i provided in the comment.
after the update ef will automatically query the value for the id that is inserted, there is no need to fill in the id before the insert. ef will generate an insert sql query without id.

Cannot add an entity with a key that is already in use update operation

I am creating small application in which i have used LINQ To SQL to perform all operation to database.
Now here i am giving the small part of my database structure please take a look.
So update language detail i am getting the object of login using the datacontext something like this.
XVDataContext Context = new XVDataContext ();
var myQuery = from objLogIn in Context.GetTable<LogIn>() where objLogIn.Emp_Id == nEmpId select objLogIn;
In nEmpId i will always have some value.
So it is not creating any problem in fact i am getting the required record from DB and storing it in objUser object using the following code.
LogIn objUser = myQuery.First<LogIn>();
Now to update LanguageDetail i am executing following code but it throws Exception when i execute SubmitChanges line.
Here is the code that i am executing to update.
LanguageDetail obj = new LanguageDetail();
foreach (string sLanguages in TextBoxLanguagesKnown.Text.Split('\n'))
{
obj.Emp_Id = objUser.Emp_Id;
obj.Language = sLanguages.Trim();
}
objUser.LanguageDetails[0] = obj;
Context.SubmitChanges();
I already read following links.
cannot add an entity with a key that is already in use
LINQ To SQL exception with Attach(): Cannot add an entity with a key that is alredy in use
Cannot add an entity with a key that is already in use (LINQ)
By reading the above links i found that i am doing some mistake in ID fields but still i am unable to resolve.
Please tell me the clear understanding of raising this issue and how can i resolve this.
EDIT:
I simply want to update LanguageDetail table.
When i try to add new object using following code it still throws exception.
objUser.LanguageDetail.Add(obj);

You might want to add / remove languages for specific user by using following code.
var languages = TextBoxLanguagesKnown.Text.Split('\n');
// Removes deleted languages (first find all language details that are missing from the UI).
var deletedLanguages = objUser.LanguageDetails.Where(ld => !languages
.Any(l => ld.Language == l.Trim())).ToArray();
foreach(var deletedLanguage in deletedLanguages)
{
objUser.LanguageDetails.Remove(deletedLanguage);
Context.LanguageDetails.DeleteOnSubmit(deletedLanguage);
}
// Adds new languages (then adds new language details that are not found in the database).
var newLanguages = languages.Where(l => !objUser.LanguageDetails
.Any(ld => ld.Language == l.Trim())).ToArray();
foreach (string newLanguage in newLanguages)
{
var languageDetail = new LanguageDetail
{
Emp_Id = objUser.Emp_Id,
Language = newLanguage.Trim()
};
objUser.LanguageDetails.Add(languageDetail);
}
Context.SubmitChanges();

From my understanding you want to update the LanguageDetail entity in your database. In order to do so you have to do one of the following:
Retrieve the original LanguageDetail object based on its id, and update that object instead of creating a new one and assigning it the id of an existing object.
Attach the newly created object to your context instead of just giving a reference to it to your LanguageDetails collection.
The exception you are seeing happens because the way linq to sql behaves is that it threats the obj as a new object that you want to insert and because of that it tries to insert it into the language details table.
Modifying your code like that should work:
Context.LanguageDetails.Attach(obj);
objUser.Employee_LanguageDetails[0] = obj;

LINQ to Entities- SaveChanges take too much time

Currently, I am struggling with an issue regarding Entity Framework (LINQ to Entities). Most of the time when I try to execute entity.SaveChanges() everything works fine but at some points entity.SaveChanges() takes too much and timesouts. I searched a lot but was unable to find out the answer.
(According to companies policy, I cannot copy code somewhere else. So, I do not have the exact code but I will try to layout the basic structure. I hope it helps you to figure out the problem but if i doesn't then let me know.)
Task:
My task is to scan the whole network for some specific files. Match content of each file with the content of database and based on the matching either insert or update the database with the content of the file. I have around 3000 files on the network.
Problem:
public void PerformAction()
{
DbTransaction tran = null;
entity.Connection.Open(); //entity is a global variable declared like myDatabaseEntity entity = new myDatabaseEntity();
tran = entity.Connection.BeginTransaction();
foreach(string path in listOfPaths)
{
//returns 1 - Multiple matching in database OR
// 2 - One matching file in database OR
// 3 - No Matching found.
int returnValue = SearchDatabase();
if(returnValue == 1)
DoSomething(); //All inserts/updates work perfectly. Save changes also works correctly.
else if(returnValue == 2)
DoSomething(); //Again, everything ok. SaveChanges works perfectly here.
else
{
//This function uses some XML file to generate all the queries dynamically
//Forexample INSERT INTO TABLEA(1,2,3);
GenerateInsertQueriesFromXML();
ExecuteQueries();
SaveChanges(); <---- Problem here. Sometimes take too much time.
}
//Transaction commit/rollback code here
}
}
public bool ExecuteQueries()
{
int result = 0;
foreach(string query in listOfInsertQueries)
{
result = entity.ExecuteStoreCommand(query); //Execute the insert queries
if(result <=0)
return false;
}
entity.TestEntityA a = new entity.TestEntityA();
a.PropertyA = 123;
a.PropertyB = 345;
//I have around 25 properties here
entity.AddToTestEntityA(a);
return true;
}

Found the issue.
The main table where i was inserting all the data had a trigger on INSERT and DELETE.
So, whenever i inserted some new data in the main table, the trigger was firing in the backend and was taking all the time.
Entity framework is FAST and INNOCENT :D

Bulk inserts and duplicate records with LINQ to SQL

Is there a "best practice" way of handling bulk inserts (via LINQ) but discard records that may already be in the table? Or I am going to have to either do a bulk insert into an import table then delete duplicates, or insert one record at a time?
08/26/2010 - EDIT #1:
I am looking at the Intersect and Except methods right now. I am gathering up data from separate sources, converting into a List, want to "compare" to the target DB then INSERT just the NEW records.
List<DTO.GatherACH> allACHes = new List<DTO.GatherACH>();
State.IState myState = null;
State.Factory factory = State.Factory.Instance;
foreach (DTO.Rule rule in Helpers.Config.Rules)
{
myState = factory.CreateState(rule.StateName);
List<DTO.GatherACH> stateACHes = myState.GatherACH();
allACHes.AddRange(stateACHes);
}
List<Model.ACH> newRecords = new List<Model.ACH>(); // Create a disconnected "record set"...
foreach (DTO.GatherACH record in allACHes)
{
var storeInfo = dbZach.StoreInfoes.Where(a => a.StoreCode == record.StoreCode && (a.TypeID == 2 || a.TypeID == 4)).FirstOrDefault();
Model.ACH insertACH = new Model.ACH
{
StoreInfoID = storeInfo.ID,
SourceDatabaseID = (byte)sourceDB.ID,
LoanID = (long)record.LoanID,
PaymentID = (long)record.PaymentID,
LastName = record.LastName,
FirstName = record.FirstName,
MICR = record.MICR,
Amount = (decimal)record.Amount,
CheckDate = record.CheckDate
};
newRecords.Add(insertACH);
}
The above code builds the newRecords list. Now, I am trying to get the records from this List that are not in the DB by comparing on the 3 field Unique Index:
AchExceptComparer myComparer = new AchExceptComparer();
var validRecords = dbZach.ACHes.Intersect(newRecords, myComparer).ToList();
The comparer looks like:
class AchExceptComparer : IEqualityComparer<Model.ACH>
{
public bool Equals(Model.ACH x, Model.ACH y)
{
return (x.LoanID == y.LoanID && x.PaymentID == y.PaymentID && x.SourceDatabaseID == y.SourceDatabaseID);
}
public int GetHashCode(Model.ACH obj)
{
return base.GetHashCode();
}
}
However, I am getting this error:
LINQ to Entities does not recognize the method 'System.Linq.IQueryable1[MisterMoney.LARS.ZACH.Model.ACH] Intersect[ACH](System.Linq.IQueryable1[MisterMoney.LARS.ZACH.Model.ACH], System.Collections.Generic.IEnumerable1[MisterMoney.LARS.ZACH.Model.ACH], System.Collections.Generic.IEqualityComparer1[MisterMoney.LARS.ZACH.Model.ACH])' method, and this method cannot be translated into a store expression.
Any ideas? And yes, this is completely inline with the original question. :)

You can't do bulk inserts with LINQ to SQL (I presume you were referring to LINQ to SQL when you said "LINQ"). However, based on what you're describing, I'd recommend checking out the new MERGE operator of SQL Server 2008.
Inserting, Updating, and Deleting Data by Using MERGE
Another example here.

I recommend you just write the SQL yourself to do the inserting, I find it is a lot faster and you can get it to work exactly how you want it to. When I did something similar to this (just a one-off program) I just used a Dictionary to hold the ID's I had inserted already, to avoid duplicates.
I find LINQ to SQL is good for one record or a small set that does its entire lifespan in the LINQ to SQL.
Or you can try to use SQL Server 2008's Bulk Insert .

One thing to watch out for is if you queue more than 2000 or so records without calling SubmitChanges() - TSQL has a limit on the number of statements per execution, so you cannot simply queue up every record and then call SubmitChanges() as this will throw an SqlException, you need to periodically clear the queue to avoid this.