Lets say I query the database and load a list of items. Then I open one of the items in a detail view form, and instead of re-querying the item out of the database, I create an instance of the item from the datasource in the list.
Is there a way I can update the database record without fetching the record of the individual item?
Here is a sample how I am doing it now:
dataItem itemToUpdate = (from t in dataEntity.items
where t.id == id
select t).FirstOrDefault();
Then after pulling the record I update some values in the item and push the record back:
itemToUpdate.itemstatus = newStatus;
dataEntity.SaveChanges();
I would think there would be a better way to do this, any ideas?
You should use the Attach() method.
Attaching and Detaching Objects
You can also use direct SQL against the database using the context of the datastore. Example:
dataEntity.ExecuteStoreCommand
("UPDATE items SET itemstatus = 'some status' WHERE id = 123 ");
For performance reasons, you may want to pass in variables instead of a single hard coded SQL string. This will allow SQL Server to cache the query and reuse with parameters. Example:
dataEntity.ExecuteStoreCommand
("UPDATE items SET itemstatus = 'some status' WHERE id = {0}", new object[] { 123 });
UPDATE - for EF 6.0
dataEntity.Database.ExecuteSqlCommand
("UPDATE items SET itemstatus = 'some status' WHERE id = {0}", new object[] { 123 });
The code:
ExampleEntity exampleEntity = dbcontext.ExampleEntities.Attach(new ExampleEntity { Id = 1 });
exampleEntity.ExampleProperty = "abc";
dbcontext.Entry<ExampleEntity>(exampleEntity).Property(ee => ee.ExampleProperty).IsModified = true;
dbcontext.Configuration.ValidateOnSaveEnabled = false;
dbcontext.SaveChanges();
The result TSQL:
exec sp_executesql N'UPDATE [dbo].[ExampleEntities]
SET [ExampleProperty ] = #0
WHERE ([Id] = #1)
',N'#0 nvarchar(32),#1 bigint',#0='abc',#1=1
Note:
The "IsModified = true" line, is needed because when you create the new ExampleEntity object (only with the Id property populated) all the other properties has their default values (0, null, etc). If you want to update the DB with a "default value", the change will not be detected by entity framework, and then DB will not be updated.
In example:
exampleEntity.ExampleProperty = null;
will not work without the line "IsModified = true", because the property ExampleProperty, is already null when you created the empty ExampleEntity object, you needs to say to EF that this column must be updated, and this is the purpose of this line.
If the DataItem has fields EF will pre-validate (like non-nullable fields), we'll have to disable that validation for this context:
DataItem itemToUpdate = new DataItem { Id = id, Itemstatus = newStatus };
dataEntity.Entry(itemToUpdate).Property(x => x.Itemstatus).IsModified = true;
dataEntity.Configuration.ValidateOnSaveEnabled = false;
dataEntity.SaveChanges();
//dataEntity.Configuration.ValidateOnSaveEnabled = true;
Otherwise we can try satisfy the pre-validation and still only update the single column:
DataItem itemToUpdate = new DataItem
{
Id = id,
Itemstatus = newStatus,
NonNullableColumn = "this value is disregarded - the db original will remain"
};
dataEntity.Entry(itemToUpdate).Property(x => x.Itemstatus).IsModified = true;
dataEntity.SaveChanges();
Assuming dataEntity is a System.Data.Entity.DbContext
You can verify the query generated by adding this to the DbContext:
/*dataEntity.*/Database.Log = m => System.Diagnostics.Debug.Write(m);
Now native support for this in EF Core 7 — ExecuteUpdate:
Finally! After a long wait, EF Core 7.0 now has a natively supported way to run UPDATE (and also DELETE) statements while also allowing you to use arbitrary LINQ queries (.Where(u => ...)), without having to first retrieve the relevant entities from the database: The new built-in method called ExecuteUpdate — see "What's new in EF Core 7.0?".
ExecuteUpdate is precisely meant for these kinds of scenarios, it can operate on any IQueryable instance, and lets you update specific columns on any number of rows, while always issuing a single UPDATE statement behind the scenes, making it as efficient as possible.
Usage:
Imagine you wanted to update the Email column of a specific user:
dbContext.Users
.Where(u => u.Id == someId)
.ExecuteUpdate(b =>
b.SetProperty(u => u.Email, "NewEmail#gmail.com")
);
As you can see, calling ExecuteUpdate requires you to make calls to the SetProperty method, to specify which property to update, and also what new value to assign to it.
EF Core will translate this into the following UPDATE statement:
UPDATE [u]
SET [u].[Email] = "NewEmail#gmail.com"
FROM [Users] AS [u]
WHERE [u].[Id] = someId
Also, ExecuteDelete for deleting rows:
There's also a counterpart to ExecuteUpdate called ExecuteDelete, which, as the name implies, can be used to delete a single or multiple rows at once without having to first fetch them.
Usage:
// Delete all users that haven't been active in 2022:
dbContext.Users
.Where(u => u.LastActiveAt.Year < 2022)
.ExecuteDelete();
Similar to ExecuteUpdate, ExecuteDelete will generate DELETE SQL statements behind the scenes — in this case, the following one:
DELETE FROM [u]
FROM [Users] AS [u]
WHERE DATEPART(year, [u].[LastActiveAt]) < 2022
Other notes:
Keep in mind that both ExecuteUpdate and ExecuteDelete are "terminating", meaning that the update/delete operation will take place as soon as you call the method. You're not supposed to call dbContext.SaveChanges() afterwards.
If you're curious about the SetProperty method, and you're confused as to why ExectueUpdate doesn't instead receive a member initialization expression (e.g. .ExecuteUpdate(new User { Email = "..." }), then refer to this comment (and the surrounding ones) on the GitHub issue for this feature.
Furthermore, if you're curious about the rationale behind the naming, and why the prefix Execute was picked (there were also other candidates), refer to this comment, and the preceding (rather long) conversation.
Both methods also have async equivalents, named ExecuteUpdateAsync, and ExecuteDeleteAsync respectively.
I recommend using Entity Framework Plus
Updating using Entity Framework Core can be very slow if you need to update hundreds or thousands of entities with the same expression. Entities are first loaded in the context before being updated which is very bad for the performance and then, they are updated one by one which makes the update operation even worse.
EF+ Batch Update updates multiple rows using an expression in a single database roundtrip and without loading entities in the context.
// using Z.EntityFramework.Plus; // Don't forget to include this.
// UPDATE all users inactive for 2 years
var date = DateTime.Now.AddYears(-2);
ctx.Users.Where(x => x.LastLoginDate < date)
.Update(x => new User() { IsSoftDeleted = 1 });
Simple and elegant extension method:
I've written an extension method for DbContext that does exactly what the OP asked for.
In addition to that, it only requires you to provide a member initialization expression (e.g. new User { ... }), and it then figures out on its own what properties you've changed, so you won't have to specify them by hand:
public static void UpdateEntity<TEntity>(
this DbContext context,
int id,
Expression<Func<TEntity>> updateExpression
) where TEntity : BaseEntity, new()
{
if (updateExpression.Body is not MemberInitExpression memberInitExpr)
throw new ArgumentException("The update expression should be a member initialization.");
TEntity entityToUpdate = updateExpression.Compile().Invoke();
entityToUpdate.Id = id;
context.Attach(entityToUpdate);
var updatedPropNames = memberInitExpr.Bindings.Select(b => b.Member.Name);
foreach (string propName in updatedPropNames)
context.Entry(entityToUpdate).Property(propName).IsModified = true;
}
You also need a BaseEntity class or interface that has your primary key in it, like:
public abstract class BaseEntity
{
public int Id { get; set; }
}
Usage:
Here's how you'd use the method:
dbContext.UpdateEntity(1234 /* <- this is the ID */, () => new User
{
Name = "New Name",
Email = "TheNewEmail#gmail.con",
});
dbContext.SaveChanges();
Nice and simple! :D
And here's the resulting SQL that gets generated by Entity Framework:
UPDATE [Users]
SET [Name] = #p0, [Email] = #p1
WHERE [Id] = #p2;
Limitation:
This method only allows you to update a single row using its primary key.
So, it doesn't work with .Where(...), IQueryable<...>, and so on. If you don't have the PK, or you want to bulk-update, then this wouldn't be your best option. In general, if you have more complex update operations, then I'd recommend you use Entity Framework Plus, or similar libraries.
It works somewhat different in EF Core:
There may be a faster way to do this in EF Core, but the following ensures an UPDATE without having to do a SELECT (tested with EF Core 2 and JET on the .NET Framework 4.6.2):
Ensure your model does not have IsRequired properties
Then use the following template (in VB.NET):
Using dbContext = new MyContext()
Dim bewegung = dbContext.MyTable.Attach(New MyTable())
bewegung.Entity.myKey = someKey
bewegung.Entity.myOtherField = "1"
dbContext.Entry(bewegung.Entity).State = EntityState.Modified
dbContext.Update(bewegung.Entity)
Dim BewegungenDescription = (From tp In dbContext.Model.GetEntityTypes() Where tp.ClrType.Name = "MyTable" Select tp).First()
For Each p In (From prop In BewegungenDescription.GetProperties() Select prop)
Dim pp = dbContext.Entry(bewegung.Entity).Property(p.Name)
pp.IsModified = False
Next
dbContext.Entry(bewegung.Entity).Property(Function(row) row.myOtherField).IsModified = True
dbContext.SaveChanges()
End Using
ef core 7 :
public async Task<int> Update(UpdateLevelVm vm)
{
return await _db.Levels.Where(l => l.Id == vm.LevelId)
.ExecuteUpdateAsync(u => u
.SetProperty(l => l.GradeId, vm.GradeId)
.SetProperty(l => l.Title, vm.Title)
);
}
this has worked for me in EF core 3.1
await _unitOfWork.Context.Database.ExecuteSqlRawAsync("UPDATE Student SET Age = 22 Where StudentId = 123");
Generally speaking, if you used Entity Framework to query all the items, and you saved the entity object, you can update the individual items in the entity object and call SaveChanges() when you are finished. For example:
var items = dataEntity.Include("items").items;
// For each one you want to change:
items.First(item => item.id == theIdYouWant).itemstatus = newStatus;
// After all changes:
dataEntity.SaveChanges();
The retrieval of the one item you want should not generate a new query.
Related
I have a database and a set of tables that already have data in.
I am using code first. Now I have been asked to add a Category table to the database and with that, to change some of the other tables to reference that table via a foreign key.
I know through previous experience, that if I update the database after changing the models, it will moan because an FK can't have 0.
So I want to use the Seed method to actually update the Foreign Keys as the database is updated.
I want to do something like this:
protected override void Seed(DatabaseContext context)
{
// Create our categories
context.Categories.AddOrUpdate(m => m.Id,
new Category { Id = 1, Name = "Cameras" },
new Category { Id = 2, Name = "Televisions" }
);
// Get all our current feeds
var feeds = context.Feeds.ToList();
context.Feeds.AddOrUpdate(m => m.Id, feeds.Select(m => m.CategoryId = 1).ToArray());
}
Can someone let me know how I might actually do this? Or if there is another way of doing it?
Inside a loop:
foreach(var f in context.Feeds)
{
f.CategoryId=1;
}
context.SaveChanges();
Or using Entity Framework Extended library to do it in one batch:
context.Feeds.Update(f=>new Feed{CategoryId=1});
I have activated migrations on my Azure Mobile Services project. I filled the new seed function Inside the Configuration.cs class of the migrations. If the tables are empty, the seed function is going without any problems. When my AddorUpdate tries to update the first object I get the error in the inner exception : "Modifying a column with the 'Identity' pattern is not supported. Column: 'CreatedAt'. Table: 'CodeFirstDatabaseSchema.Category'."
Part of my code is as follows:
context.categories.AddOrUpdate(
new Category { Id="1", Code="GEN", Text="General"},
new Category { Id="2", Code="POL", Text="Politics"},
new Category { Id="3", Code="FAS", Text="Fashion"},
new Category { Id="4", Code="PEO", Text="People"},
new Category { Id="5", Code="TEC", Text="Technology"},
new Category { Id="6", Code="SPO", Text="Sport"},
new Category { Id="7", Code="LIV", Text="Living"}
);
Here's my generic implementation of Nikatlas' solution.
Short version of the answer: You can't modify CreatedAt with a null value, so you can use this function instead:
private void AddOrUpdatePreservingCreatedAt<T> (DbSet<T> set, T item) where T : EntityData
{
var existing = set.Where(i => i.Id == item.Id).FirstOrDefault();
if (existing != null)
{
item.CreatedAt = existing.CreatedAt;
}
set.AddOrUpdate(i => i.Id, item);
}
Call it like this
AddOrUpdatePreservingCreatedAt(context.YourItems, itemToBeUpdatedOrAdded);
It seems i have found a solution to this problem.
The reason this error occurs is because of the AddOrUpdate Method.
As stated in this post : http://thedatafarm.com/data-access/take-care-with-ef-4-3-addorupdate-method/
More importantly, if a match is found then the update will update all and null out any that weren’t in your AddOrUpdate.
What this means is that after the first seed, whenever your code runs it tries to update your entities correctly but it tries to pass the value null on CreatedAt field. If you look at EntityData class the CreateAt field has these attributes :
[DatabaseGenerated(DatabaseGeneratedOption.Identity)] //Here they mark this as IDENTITY
[Index(IsClustered = true)] // Cluster index. i really dont know why ?
[TableColumn(TableColumnType.CreatedAt)]
public DateTimeOffset? CreatedAt { get; set; }
So the error occurs beacause you try to modify the CreatedAt column.
My solution was to Create a List, lookup to set CreatedAt to correct value and then addOrUpdate:
// Create List
List<Permission> permissions = new List<Permission>(new Permission[]{
new Permission { Id = "ID1" , Name = "Send SMS"},
new Permission { Id = "ID2", Name = "Send Email"} });
// Iterate through list to set CreatedAt to correct value
foreach (Permission p in permissions){
// Get the record from the db if it exists
var t = context.PermissionSet.Where(s => s.Id == p.Id).FirstOrDefault();
if (t != null){
p.CreatedAt = t.CreatedAt; //SET CreatedAt to correct Value if the record already exists
}
context.PermissionSet.AddOrUpdate(a => a.Id, p); // NOW I CAN UPDATE WITH NO PROBLEM
}
Hope this helps. :)
If you have a integer column named Id, then Entity Framework will assume that is the primary key and that it is database generated - so it is created as an IDENTITY column in the database.
You cannot specify the Id for IDENTITY columns, so you stop doing that by removing the Id = 1, Id = 2, etc
I am a bit thrown by the fact that the column you have a problem with is named "CreatedAt". It sounds like it should be a DateTime and might also be database generated, but it surely shouldn't be IDENTITY?
Anyways, the usage you probably want is the one where you specify the natural key of the entity, so that EF can identify any records that already exist. So, if CODE is the natural key then you should be writing the Seed like this:
context.categories.AddOrUpdate(
x => x.Code,//the natural key is Code
new Category { Code="GEN", Text="General"},
new Category { Code="POL", Text="Politics"},
new Category { Code="FAS", Text="Fashion"},
new Category { Code="PEO", Text="People"},
new Category { Code="TEC", Text="Technology"},
new Category { Code="SPO", Text="Sport"},
new Category { Code="LIV", Text="Living"}
);
Reference:
Take care with the AddOrUpdate method
This question, its answers and comments might help you a bit, but not much.
You can do Inserts on identity column using the solutions provided by the question. But you cannot update values of Identity Column. The only way to do updates on identity column is to mark it as not being identity. Probably by adding manual migrations.
This SO question and its answers may also be helpful.
Read here also on general MSSQL Server constraints on Updating Identity Column.
SAME PROBLEM AND SOLUTION
We had the same problem and it was a trigger in another table that had impact on the table that we had the problem on.
DETAILS OF OUR DEVELOPMENT
We developed a Xamarin App connected to an Azure Web Service. When we used the method PushAsync from iMobileServices, it gave us the error: Modifying a column with the 'Identity' pattern is not supported. Column: 'CreatedAt'.
It was strange for us as some tables did not have the problem with the web service
REASON
It seems that the trigger update got in conflict with the pushasync from the mobile device.
We disabled the trigger, switched the responsibility to the front end and it worked fine. At least for us.
We hope this soltion helps someone.
I have simple entity:
public class Hall
{
[Key]
public int Id {get; set;}
public string Name [get; set;}
}
Then in the Seed method I use AddOrUpdate to populate table:
var hall1 = new Hall { Name = "French" };
var hall2 = new Hall { Name = "German" };
var hall3 = new Hall { Name = "Japanese" };
context.Halls.AddOrUpdate(
h => h.Name,
hall1,
hall2,
hall3
);
Then I run in the Package Management Console:
Add-Migration Current
Update-Database
It's all fine: I have three rows in the table "Hall". But if I run in the Package Management Console Update-Database again I have already five rows:
Id Name
1 French
2 Japaneese
3 German
4 French
5 Japanese
Why? I think it is should be three rows again, not five. I tried to use Id property instead of Name but it does not make the difference.
UPDATE:
This code produces the same result:
var hall1 = new Hall { Id = 1, Name = "French" };
var hall2 = new Hall { Id = 2, Name = "German" };
var hall3 = new Hall { Id = 3, Name = "Japanese" };
context.Halls.AddOrUpdate(
h => h.Id,
hall1);
context.Halls.AddOrUpdate(
h => h.Id,
hall2);
context.Halls.AddOrUpdate(
h => h.Id,
hall3);
Also I have the latest EntityFramework installed via nuget.
Ok I was banging my face off the keyboard for an hour with this. If your table's Id field is an Identity field then it won't work so use a different one for identifierExpression. I used the Name property and also removed the Id field from the new Hall {...} initializer.
This tweak to the OPs code worked for me so I hope it helps someone:
protected override void Seed(HallContext context)
{
context.Halls.AddOrUpdate(
h => h.Name, // Use Name (or some other unique field) instead of Id
new Hall
{
Name = "Hall 1"
},
new Hall
{
Name = "Hall 2"
});
context.SaveChanges();
}
I know this is an old question, but the right answer is that if you are setting the id # yourself and you want to use AddOrUpdate then you need to tell EF/SQL that you don't want it to generate the ID #.
modelBuilder.Entity<MyClass>().Property(p => p.Id)
.HasDatabaseGeneratedOption(System.ComponentModel
.DataAnnotations.Schema.DatabaseGeneratedOption.None);
The down side to this is that when you insert a new item you need to set it's Id, so if this is done dynamically at runtime (instead of from seed data) then you will need to calculate out the next Id. Context.MyClasses.Max(c=>c.Id) + 1 works well.
This code works:
public Configuration()
{
AutomaticMigrationsEnabled = true;
}
protected override void Seed(HallContext context)
{
context.Halls.AddOrUpdate(
h => h.Id,
new Hall
{
Id = 1,
Name = "Hall 1"
},
new Hall
{
Id = 2,
Name = "Hall 2"
});
context.SaveChanges();
}
This can also be caused if you're setting the Entity State incorrectly. I kept getting the following error when I'd run update-database..."Sequence contains more than one matching element."
For example, I had duplicate rows being created on each update-database command (which of course is not supposed to happen when seeding data), and then the next update-database command wouldn't work at all since it found more than one match (hence the sequence error saying I have more than one matching row). That's because I had overridden SaveChanges in my context file with a method call to ApplyStateChanges...
public override int SaveChanges()
{
this.ApplyStateChanges();
return base.SaveChanges();
}
I was using ApplyStateChanges to ensure that when adding object graphs, Entity Framework knows explicitly whether the object is in an added or modified state. The entire explanation on how I'm using ApplyStateChanges can be found here.
And this works great (but the caveat!!)...if you're also seeding the database using CodeFirst migrations, then the above method will cause havoc for the AddOrUpdate() call within the Seed Method. So before anything else, just check your DBContext file and ensure you're not overriding SaveChanges in the way above, or you will end up getting duplicate data running the update-database command a second time, and then won't work at all the third time since there's more than one row for each matching item.
When it comes down to it, you don't need to configure the Id in AddOrUpdate()...that defeats the whole purpose of easy and initial database seeding. It works fine by something like:
context.Students.AddOrUpdate(
p => p.StudentName,
new Student { StudentName = "Bill Peters" },
new Student { StudentName = "Jandra Nancy" },
new Student { StudentName = "Rowan Miller" },
new Student { StudentName = "James O'Dalley" },
just AS LONG as I'm not overriding the SaveChanges method in my context file with a call to ApplyStateChanges. Hope this helps.
These steps worked for me
Delete all the rows in the table.
Reset the incremental identity to 0. DBCC CHECKIDENT (yourtablename, RESEED, 0) (The primary keys specified in the Seed() must match those in the database table so that they do not duplicate.)
Specify the primary keys in the 'seed' method.
Run the Seed() method several times and you check if they duplicated.
I have found that AddOrUpdate works fine with fields that are not ID's. If this works for you: context.Halls.AddOrUpdate(h => h.Name, hall1, hall2, hall3)
You may want to use Hall names like 'French_test_abc_100', 'German_test_abc_100' etc.
That stops hard coded test data messing things up when you are testing your app.
If object(hall)'s id is 0, it is a insertion. I think you need to double check the id field of your hall objects
Is your ID field an Identity field? I was running into this same issue. When I removed the Identity status from my ID field and set the IDs going into the database, that resolved the issue.
That worked for me, since these were look-up tables and shouldn't have been identity fields, anyway.
I used the ID field as Identity/Key and add attributes not to assign Ids by the server. This solved the problem for me.
public class Hall
{
[Key]
[Required]
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public int Id {get; set;}
public string Name [get; set;}
}
Just to Ciaren's answer, the below code of resetting the context on ModelCreating, helped me resolve similar issues. Make sure change "ApplicationContext" to your DbContext name.
public class ApplicationContext : DbContext, IDbContext
{
public ApplicationContext() : base("ApplicationContext")
{
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();
Database.SetInitializer<ApplicationContext>(null);
base.OnModelCreating(modelBuilder);
}
}
I found out that for this to work, the identity position should be 0 when the seed first run. You can reset it using:
DBCC CHECKIDENT (tableName, RESEED, 0)
I think it's likely that you need to back out existing database migrations (i.e. start your database from scratch) with something like Update-Database TargetMigration:0 followed by Update-Database.
As it is, you're not dropping the existing table or values, you're just add/updating those values. That needs to happen in order to get your desired result.
You could have also done this:
context.Halls.AddOrUpdate(new Hall[]{hall1,hall2, hall3});
I need to get the list of changed fields only, the datastore is ssce so no triggers are available
Is there any support in EF to get a list or to build a generic component ?
Depending on the type of context and generated entities you can do it in several different ways.
In case of objects inherited from Entity or POCO you can use ObjectStateManager
in case of Self-Tracking entities you can use Tracker from entity itself.
please provide more details on the way how you generated context and how you make changes
EDITED(2):
you can query ObjectStateManager for changed entries simply like this:
var changed = ctx.ObjectStateManager.GetObjectStateEntries().Where(e=>e.State != EntityState.Unchanged);
EDITED(1):
The following example from MSDN demonstrate how to query for changes:
int orderId = 43680;
using (AdventureWorksEntities context =
new AdventureWorksEntities())
{
var order = (from o in context.SalesOrderHeaders
where o.SalesOrderID == orderId
select o).First();
// Get ObjectStateEntry from EntityKey.
ObjectStateEntry stateEntry =
context.ObjectStateManager
.GetObjectStateEntry(((IEntityWithKey)order).EntityKey);
//Get the current value of SalesOrderHeader.PurchaseOrderNumber.
CurrentValueRecord rec1 = stateEntry.CurrentValues;
string oldPurchaseOrderNumber =
(string)rec1.GetValue(rec1.GetOrdinal("PurchaseOrderNumber"));
//Change the value.
order.PurchaseOrderNumber = "12345";
string newPurchaseOrderNumber =
(string)rec1.GetValue(rec1.GetOrdinal("PurchaseOrderNumber"));
// Get the modified properties.
IEnumerable<string> modifiedFields = stateEntry.GetModifiedProperties();
foreach (string s in modifiedFields)
Console.WriteLine("Modified field name: {0}\n Old Value: {1}\n New Value: {2}",
s, oldPurchaseOrderNumber, newPurchaseOrderNumber);
// Get the Entity that is associated with this ObjectStateEntry.
SalesOrderHeader associatedEnity = (SalesOrderHeader)stateEntry.Entity;
Console.WriteLine("Associated Enity's ID: {0}", associatedEnity.SalesOrderID);
}
It's commonly a good practice to do this by using the database structure itself.
This is just another approach to the one you have now.
You can create a new field of type datetime in a table called for example ModifiedOn and update it every time that you update the row in the database.
Then when you want the changed rows after a specific time you just use:
where ModifiedOn > dateTime
It's just another suggestion on how you can approach the problem from a different angle.
with my Repository classes, I use LinqToSql to retrieve the data from the repository (eg. Sql Server 2008, in my example). I place the result data into a POCO object. Works great :)
Now, if my POCO object has a child property, (which is another POCO object or an IList), i'm trying to figure out a way to populate that data. I'm just not too sure how to do this.
Here's some sample code i have. Please note the last property I'm setting. It compiles, but it's not 'right'. It's not the POCO object instance .. and i'm not sure how to code that last line.
public IQueryable<GameFile> GetGameFiles(bool includeUserIdAccess)
{
return (from q in Database.Files
select new Core.GameFile
{
CheckedOn = q.CheckedOn.Value,
FileName = q.FileName,
GameFileId = q.FileId,
GameType = (Core.GameType)q.GameTypeId,
IsActive = q.IsActive,
LastFilePosition = q.LastFilePosition.Value,
UniqueName = q.UniqueName,
UpdatedOn = q.UpdatedOn.Value,
// Now any children....
// NOTE: I wish to create a POCO object
// that has an int UserId _and_ a string Name.
UserAccess = includeUserIdAccess ?
q.FileUserAccesses.Select(x => x.UserId).ToList() : null
});
}
Notes:
Database.Files => The File table.
Database.FilesUserAccess => the FilesUserAccess table .. which users have access to the GameFiles / Files table.
Update
I've now got a suggestion to extract the children results into their respective POCO classes, but this is what the Visual Studio Debugger is saying the class is :-
Why is it a System.Data.Linq.SqlClient.Implementation.ObjectMaterializer<..>
.Convert<Core.GameFile> and not a List<Core.GameFile> containing the POCO's?
Any suggestions what that is / what I've done wrong?
Update 2:
this is what i've done to extract the children data into their respective poco's..
// Now any children....
UserIdAccess = includeUserIdAccess ?
(from x in q.FileUserAccesses
select x.UserId).ToList() : null,
LogEntries = includeUserIdAccess ?
(from x in q.LogEntries
select new Core.LogEntry
{
ClientGuid = x.ClientGuid,
ClientIpAndPort = x.ClientIpAndPort,
// ... snip other properties
Violation = x.Violation
}).ToList() : null
I think that all you need to do is to put another Linq query in here:
q.FileUserAccesses.Select(x => x.UserId).ToList()
i.e. You want to select data from the FileUserAccess records - which I'm assuming are Linq to SQL classes, so to do this you can have something like:
(from fua in q.FileUserAccesses
select new PocoType
{
UserID = fua.UserID,
Name = fua.User.UserName // Not sure at this point where the name comes from
}).ToList()
That should get you pointed in the right direction at least.
What is the type of UserIdAccess? How is it not 'right'? Are you getting the 'wrong' data? if so have you checked your database directly to make sure the 'right' data is there?