I have a local list of values that I need to have entity framework check against the database and return them.
If the list was already in the database, the following would work:
var list = /* some ef query */;
var myList = context.Logs.Where(l => list.Any(li => l.LogNumber == li.LogNumber));
But if the list is local, it would throw an error:
var list = new List<Log>();
var myList = context.Logs.Where(l => list.Any(li => l.LogNumber == li.LogNumber));
Exception: Unable to process the type 'Data.Log[]', because it has no known mapping to the value layer.
So how can I match a local list against a database list using EF?
I got a different error than you with the code sample, but I believe it's the same idea. EF doesn't know how to translate List<Log> into a SQL store expression. It works when you're still in a query because it hasn't been serialized yet.
I realize this is less than ideal, but I was able to make this query work by extracting the scalar values of LogNumber and then using that in the query.
var list = new List<Log>();
list.Add(new Log()
{
LogNumber = 1
});
var numbers = list.Select(l => l.LogNumber);
var myList = m.Logs.Where(l => numbers.Contains(l.LogNumber));
Related
I want to find any entity that inherits from DbEntity and has the field DeletedDate set to a value older than 100 days.
I have managed to piece together this code. But I am unsure of how I can go from this to querying the database for relevant entities.
var softDeletableEntities = _applicationContext.Model.GetEntityTypes()
.Where(e =>
typeof(DbEntity).IsAssignableFrom(e.ClrType)
&& e.BaseType == null
);
foreach (var entity in softDeletableEntities)
{
var entry = _applicationContext.Entry(entity.ClrType);
entry.Property<DateTimeOffset?>("DeletedDate");
// how do I find any Entity where (DeletedDate != null) and delete it?
}
I was hoping to be able to do something like this, but Set<> can't be used like that:
// Not ok to use Set<>() as below. Gives: 'entity' is a variable but is used like a type
var dataSet = _applicationContext.Set<entity.ClrType>();
var deleteOlderThan = DateTime.Now.AddDays(-100);
var toDelete = dataSet.Where(x => x.DeletedDate < deleteOlderThan);
dataSet.RemoveRange(toDelete);
_applicationContext.SaveChanges();
Any tips :)?
I would suggest to use EF Core extension linq2db.EntityFrameworkCore, note that I'm one of the creators. Install appropriate version 5.x for EF Core 5, 6.x for EF Core 6, etc.
Then you can execute the following query:
var dataSet = _applicationContext.Set<entity.ClrType>();
var deleteOlderThan = DateTime.Now.AddDays(-100);
var toDelete = dataSet.Where(x => x.DeletedDate < deleteOlderThan);
toDelete.Delete(); // method from Extension
I have min 100 000 data into a Job_Details table and I'm using Entity Framework to map the data.
This is the code:
public GetJobsResponse GetImportJobs()
{
GetJobsResponse getJobResponse = new GetJobsResponse();
List<JobBO> lstJobs = new List<JobBO>();
using (NSEXIM_V2Entities dbContext = new NSEXIM_V2Entities())
{
var lstJob = dbContext.Job_Details.ToList();
foreach (var dbJob in lstJob.Where(ie => ie.IMP_EXP == "I" && ie.Job_No != null))
{
JobBO job = MapBEJobforSearchObj(dbJob);
lstJobs.Add(job);
}
}
getJobResponse.Jobs = lstJobs;
return getJobResponse;
}
I found to this line is taking about 2-3 min to execute
var lstJob = dbContext.Job_Details.ToList();
How can i solve this issue?
To outline the performance issues with your example: (see inline comments)
public GetJobsResponse GetImportJobs()
{
GetJobsResponse getJobResponse = new GetJobsResponse();
List<JobBO> lstJobs = new List<JobBO>();
using (NSEXIM_V2Entities dbContext = new NSEXIM_V2Entities())
{
// Loads *ALL* entities into memory. This effectively takes all fields for all rows across from the database to your app server. (Even though you don't want it all)
var lstJob = dbContext.Job_Details.ToList();
// Filters from the data in memory.
foreach (var dbJob in lstJob.Where(ie => ie.IMP_EXP == "I" && ie.Job_No != null))
{
// Maps the entity to a DTO and adds it to the return collection.
JobBO job = MapBEJobforSearchObj(dbJob);
lstJobs.Add(job);
}
}
// Returns the DTOs.
getJobResponse.Jobs = lstJobs;
return getJobResponse;
}
First: pass your WHERE clause to EF to pass to the DB server rather than loading all entities into memory..
public GetJobsResponse GetImportJobs()
{
GetJobsResponse getJobResponse = new GetJobsResponse();
using (NSEXIM_V2Entities dbContext = new NSEXIM_V2Entities())
{
// Will pass the where expression to be DB server to be executed. Note: No .ToList() yet to leave this as IQueryable.
var jobs = dbContext.Job_Details..Where(ie => ie.IMP_EXP == "I" && ie.Job_No != null));
Next, use SELECT to load your DTOs. Typically these won't contain as much data as the main entity, and so long as you're working with IQueryable you can load related data as needed. Again this will be sent to the DB Server so you cannot use functions like "MapBEJobForSearchObj" here because the DB server does not know this function. You can SELECT a simple DTO object, or an anonymous type to pass to a dynamic mapper.
var dtos = jobs.Select(ie => new JobBO
{
JobId = ie.JobId,
// ... populate remaining DTO fields here.
}).ToList();
getJobResponse.Jobs = dtos;
return getJobResponse;
}
Moving the .ToList() to the end will materialize the data into your JobBO DTOs/ViewModels, pulling just enough data from the server to populate the desired rows and with the desired fields.
In cases where you may have a large amount of data, you should also consider supporting server-side pagination where you pass a page # and page size, then utilize a .Skip() + .Take() to load a single page of entries at a time.
My goal is to modify "JustMyCode" queries using nDepend API. I am using code like:
var justMyCodeGroup = prj.CodeQueries.CodeQueriesSet.ChildGroups.Single(x => x.Name.Contains("JustMyCode"));
var originalQuery = justMyCodeGroup.ChildQueries
.Single(x => x.QueryString.Contains("Discard generated Types from JustMyCode"));
var changedQuery = originalQuery.Controller.CreateQuery(originalQuery.IsActive,
query,
originalQuery.
DisplayStatInReport,
originalQuery.DisplayListInReport,
originalQuery.DisplaySelectionViewInReport,
originalQuery.IsCriticalRule);
var justMyCodeGroupWithModifiedQuery = justMyCodeGroup.ReplaceQuery(originalQuery, changedQuery);
prj.CodeQueries.CodeQueriesSet.ReplaceGroup(justMyCodeGroup, justMyCodeGroupWithModifiedQuery);
However, when I run the code above I get ArgumentException with message:
newGroup.Controller is different than this groupOfGroups.Controller
Any help ?
Update 1:
I also tried code:
var justMyCodeGroup = prj.CodeQueries.CodeQueriesSet.ChildGroups.Single(x => x.Name.Contains("JustMyCode"));
var originalQuery = justMyCodeGroup.ChildQueries
.Single(x => x.QueryString.Contains("Discard generated Types from JustMyCode"));
var changedQuery = originalQuery.Controller.CreateQuery(originalQuery.IsActive,
query,
originalQuery.
DisplayStatInReport,
originalQuery.DisplayListInReport,
originalQuery.DisplaySelectionViewInReport,
originalQuery.IsCriticalRule);
var justMyCodeGroupWithModifiedQuery = justMyCodeGroup.ReplaceQuery(originalQuery, changedQuery);
var newQueries = new List<IQuery>();
foreach (var q in justMyCodeGroup.ChildQueries)
{
if (q.QueryString.Contains("Discard generated Types from JustMyCode"))
{
continue;
}
newQueries.Add(prj.CodeQueries.CodeQueriesSet.Controller.CreateQuery(q.IsActive, q.QueryString,
q.DisplayStatInReport, q.DisplayListInReport, q.DisplaySelectionViewInReport, q.IsCriticalRule));
}
newQueries.Add(prj.CodeQueries.CodeQueriesSet.Controller.CreateQuery(originalQuery.IsActive, query, originalQuery.DisplayStatInReport, originalQuery.DisplayListInReport, originalQuery.DisplaySelectionViewInReport, originalQuery.IsCriticalRule));
var newGroup = prj.CodeQueries.CodeQueriesSet.Controller.CreateGroup(justMyCodeGroup.Name,
justMyCodeGroup.IsActive, justMyCodeGroup.ShownInReport, newQueries, new List<IGroup>());
prj.CodeQueries.CodeQueriesSet.RemoveGroup(justMyCodeGroup);
prj.CodeQueries.CodeQueriesSet.AddGroup(newGroup);
Right now, RemoveGroup throws exception:
this group of groups doesn't contain groupToRemove.
Update 2:
And I also wonder, why does this code return false ?
var justMyCodeGroup = prj.CodeQueries.CodeQueriesSet.ChildGroups.Single(x => x.Name.Contains("JustMyCode"));
prj.CodeQueries.CodeQueriesSet.ContainsGroup(justMyCodeGroup)
Refer to the PowerTools source file:
$NDependInstallDir$\NDepend.PowerTools.SourceCode\CQL2CQLinq\CQL2CQLinqPowerTool.cs
This PowerTools convert code queries written with old CQL syntax into code queries written with new CQLinq syntax, hence it loads the queries set from a project, update CQL queries, and then save the new queries set in the project.
The queriesController is gathered this way...
var queriesSet = project.CodeQueries.CodeQueriesSet;
var queriesController = queriesSet.Controller;
... and then used this way to modify the queries set:
queriesController.DoUpdateQueryObject(query, newQuery);
A newbie question. I am using EntityFramework 4.0. The backend database has a function that will return a subset of records based on time.
Example of working code is:
var query = from rx in context.GetRxByDate(tencounter,groupid)
select rx;
var result = context.CreateDetachedCopy(query.ToList());
return result;
I need to verify that a record does not exist in the database before inserting a new record. Before performing the "Any" filter, I would like to populate the context.Rxes with a subset of the larger backend database using the above "GetRxByDate()" function.
I do not know how to populate "Rxes" before performing any further filtering since Rxes is defined as
IQueryable<Rx> Rxes
and does not allow "Rxes =.. ". Here is what I have so far:
using (var context = new EnityFramework())
{
if (!context.Rxes.Any(c => c.Cform == rx.Cform ))
{
// Insert new record
Rx r = new Rx();
r.Trx = realtime;
context.Add(r);
context.SaveChanges();
}
}
I am fully prepared to kick myself since I am sure the answer is simple.
All help is appreciated. Thanks.
Edit:
If I do it this way, "Any" seems to return the opposite results of what is expected:
var g = context.GetRxByDate(tencounter, groupid).ToList();
if( g.Any(c => c.Cform == rx.Cform ) {....}
I asked a question about this previously but my database structure has changed, and while it made other things simpler, now this part is more complicated. Here is the previous question.
At the time, my EF Context had a UsersProjects object because there were other properties. Now that I've simplified that table, it is just the keys, so all my EF context knows about is Users and Projects and the M2M relationship between them. There is no more UsersProjects as far as EF knows.
So my goal is to say "show me all the users who are working on projects with me."
in SQL, this would go something like:
SELECT * FROM Users INNER JOIN UsersProjects ON Users.ID=UsersProjects.UserID
WHERE ProjectID IN (SELECT ProjectID FROM UsersProjects WHERE UserID=#UserID)
and I started in EF with something like this:
var myProjects =
(from p in edmx.Projects
where p.Users.Contains(edmx.Users.FirstOrDefault(u => u.Email == UserEmail))
orderby p.Name
select p).ToList();
var associatedUsers =
(from u in edmx.Users
where myProjects.Contains(?????????)
//where myProjects.Any(????????)
select u);
The trick is finding what to put in the ????????. Anyone help here?
var me = context
.Users
.First(user => user.Email = "me#example.com");
// Note that there is no call to ToList() or AsEnumerable().
var myProjects = context
.Projects
.Where(project => project.Users.Contains(me));
var associatedUsers = context
.Users
.Where(user => myProjects.Any(project => user.Project.Contains(project)));
But there are several other possible solutions. For example
var associatedUsers = myProjects
.SelectMany(project => project.Users)
.Distinct();
which I would prefer.
Further note that it is much easier to obtain myProjects using a navigation property instead of using Contains().
var myProjects = me.Projects;
Daniel, I tried what you had and ran into some issues. Can you explain what these errors mean?
I tried:
// Doesn't work.
using (var edmx = new MayflyEntities())
{
var me = edmx.Users.First(user => user.Email == UserEmail);
var myProjects = edmx.Projects.Where(project => project.Users.Contains(me));
var associatedUsers = myProjects.SelectMany(project => project.Users).Distinct();
}
but got the two following exceptions:
Unable to create a constant value of type 'DomainModel.User'. Only primitive types ('such as Int32, String, and Guid') are supported in this context.
and
The ObjectContext instance has been disposed and can no longer be used for operations that require a connection.
So, I moved some things around and this works fine, but now I'm curious as to why? In SQL Profiler, it all executes in one query, so why does it show that the context has been disposed? Also, why can it not use the me object instead of the lambda?
// Works fine
var edmx = new MayflyEntities();
var myProjects = edmx.Projects.Where(project => project.Users.Contains(edmx.Users.First(user => user.Email == UserEmail)));
var associatedUsers = myProjects.SelectMany(project => project.Users).Distinct();