If i am updating with same records which are existing in EDMX and i want to return if update successful then return 1.
But when i am not changing any values and update EDMX it is returning 0.
How to get 1 for if same records are exist and no changes made into EDMX.
My requirement is,I am returning basically Row Changes that i know about that any changes are made or not.Is there predefined method that i returned 1 for if there is no exception occurred.
use try and catch if exception return 0 else return 1.
try
{
context.SaveChanges();
return 1;
}
catch(Exception ex)
{
//log exception here.
return 0;
}
Related
I have a intermediary table in which I want to save sbj_type_id and difficulty_level_id so I have setup this:
$difficulty_level = DifficultyLevel::find(5);
if ($difficulty_level->sbj_types()->sync($request->hard, false)) {
dd('ok');
}
else {
dd('not ok');
}
Here is my DifficultyLevel.php:
public function sbj_types() {
return $this->belongsToMany('App\SbjType');
}
and here is my SbjType.php:
public function difficulty_levels() {
return $this->hasMany('App\DifficultyLevel');
}
In the above code I have dd('ok') it's returning ok but the database table is empty.
Try to change
return $this->hasMany('App\DifficultyLevel');
to
return $this->belongsToMany('App\DifficultyLevel');
The sync() method takes an array with the id's of the records you want to sync as argument to which you can optionally add intermediate table values. While sync($request->hard, false) doesn't seem to throw an exception in your case, I don't see how this would work.
Try for example:
$difficulty_level->sbj_types()->sync([1,2,3]);
where 1,2,3 are the id's of the sbj_types.
You can read more about syncing here.
I'm trying to get some data from a database whose results can be more than one row.
I've the following code for that:
public System.Linq.IQueryable<Users> getUser2(string idUser)
{
try
{
using (Entities c = new Entities())
{
c.ContextOptions.LazyLoadingEnabled = false;
c.ContextOptions.ProxyCreationEnabled = false;
return c.Users.Include("Empresas").Where(x => x.Login == idUser && x.Empresas.Activa == true);
}
}
catch (Exception ex)
{
throw ex;
}
}
But it doesn't seem to get any result, it shows something like a badly formed Iqueryable, I mean if I expand its results view I can see a message that says "ObjectContext instance has been eliminated and cannot be used for operations that need a connection" If I try to access any Users element with the function ElementAt(index) I get an IndexOutOfBounds error as it looks like it has no data if watched on debug mode.
I've deduced that it's Where fault because this code Works fine in returning the first user it finds that fulfills the condition:
public Users getUser(string idUser)
{
try
{
using (Entities c = new Entities())
{
c.ContextOptions.LazyLoadingEnabled = false;
c.ContextOptions.ProxyCreationEnabled = false;
return c.Users.Include("Empresas").FirstOrDefault(x => x.Login == idUser && x.Empresas.Activa == true);
}
}
catch (Exception ex)
{
throw ex;
}
}
Does that Where work differently than what I think I should? If then, how could I get several data that fulfills the conditions I'm passing the same as in getUser but for several rows?
Thanks for your attention.
You need to enumerate the result, so after the "where" statement add. ToList() which will enumerate and execute the query against your database. FirstOrDefault is executing the query thats why you get a result.
You need to check the deferred methods and understand how they work.
EDIT
The following are some links to show you the deference between the Deferred method vs Immediate methods in LINQ
1- http://www.dotnetcurry.com/showarticle.aspx?ID=750
2- http://www.codeproject.com/Articles/627081/LINQ-Deferred-Execution-Lazy-Evaluation
3- http://visualcsharptutorials.com/linq/deferred-execution
Hope that helps.
I'm adding several rows to a DataTable in my strongly-typed DataSet and use a TableAdapterManager to insert the changes into my database. Using the UpdateAll function of the TableAdapterManager results in case of a failure in a database rollback of all inserted rows. Unfortunately DataTable.RejectChanges does not "rollback" the same rows in the DataTable.
In the call to DataTable.RejectChanges method only the last row is removed from the DataTable. I want the DataSet to have the same status as the database.
Isn't RejectChanges per MSDN documentation deleting all new (uncomitted) rows? Am I doing something wrong?
My code:
foreach (var item in List)
{
DataSet.customerRow custRow = ds.customer.NewcustomerRow();
custRow.name = item.Name;
try
{
ds.customer.AddcustomerRow(custRow);
}
catch (Exception ex)
{
ProcessException(ex, System.Reflection.MethodBase.GetCurrentMethod().Name);
valid=false;
}
}
if (valid)
{
DataSetTableAdapters.TableAdapterManager adapterManager = new DataSetTableAdapters.TableAdapterManager();
adapterManager.customerTableAdapter = new DataSetTableAdapters.customerTableAdapter();
try
{
retryPolicy.ExecuteAction(() =>
{
adapterManager.UpdateAll(ds);
});
}
catch (Exception ex)
{
ds.customer.RejectChanges();
}
}
else
{
ds.customer.RejectChanges();
}
The solution is to set adapterManager.BackupDataSetBeforeUpdate = true; This creates an internal backup copy of the dataset which is "reused" in case of failures.
MSDN: Hierarchical Update Overview
"The backup copy is only in memory during the execution of the TableAdapterManager.UpdateAll method. Therefore, there is no programmatic access to this backup dataset because it either replaces the original dataset or goes out of scope as soon as the TableAdapterManager.UpdateAll method has finished running."
I have a table named countries and i define the country_name field to be unique by creating a “Index/Key” of type “Unique Key” on sql servwer 2008 r2.
But currently if the user insert a country_name value that already exists on my asp.net mvc3 application, then an exception of type “System.Data.Entity.Infrastructure.DbUpdateException” will be raised , which is very general.
So is there a way to define a specific exception in case the unique constraint has been violated ??? rather than just raising the general “System.Data.Entity.Infrastructure.DbUpdateException” exception?
BR
Most likely, thought I can't test it at the moment, the inner exception of DbUpdateException is probably an exception about a duplicate or foreign key constraint. More importantly, you have an opportunity to not throw any exceptions by checking to see if a country already exists. Two ways I can think of are to; check and see if the country already exists by doing a simple select, and if it doesn't, doing an insert/add or write a stored procedure that and do a select/insert or merge and return any value(s) you want back.
Update
(this is example code to demonstrate the logic flow of events and not good programming practice, specially by catching all excepts)
Exception Logic
public AddCountry(string countryTitle)
{
using (var db = new DbContext(_connectionString)
{
try
{
// Linq to (SQL/EF)-ish code
Country country = new Country();
country.ID = Guid.NewGuid();
country.Title = countryTitle;
db.Countrys.Add(country);
db.SubmitChanges(); // <--- at this point a country could already exist
}
catch (DbUpdateException ex)
{
// <--- at this point a country could be delete by another user
throw Exception("Country with that name already exists");
}
}
}
Non-Exception Logic
public AddCountry(string countryTitle)
{
using (var db = new DbContext(_connectionString)
{
using (TransactionScope transaction = new TransactionScope())
{
try
{
Country country = db.Countries
.FirstOrDefault(x => x.Title = countryTitle);
if (country == null)
{
country = new Country();
country.ID = Guid.NewGuid();
country.Title = countryTitle;
db.Countrys.Add(country);
db.SubmitChanges(); // <--- at this point a country
// shouldn't exist due to the transaction
// although someone with more expertise
// on transactions with entity framework
// would show how to use transactions properly
}
}
catch (<someTimeOfTransactionException> ex)
{
// <--- at this point a country with the same name
// should not exist due to the transaction
// this should really only be a deadlock exception
// or an exception outside the scope of the question
// (like connection to sql lost, etc)
throw Exception("Deadlock exception, cannot create country.");
}
}
}
}
Most likely the TransactionScope(Transaction transactionToUse) Constructor would be needed and configured properly. Probably with an Transactions.IsolationLevel set to Serializable
I would also recommend reading Entity Framework transaction.
I have the following test case
[TestMethod()]
[DeploymentItem("Courses.sdf")]
public void RemoveCourseConfirmedTest()
{
CoursesController_Accessor target = new CoursesController_Accessor();
int id = 50;
ActionResult actual;
CoursesDBContext db = target.db;
Course courseToDelete = db.Courses.Find(id);
List<CourseMeet> meets = courseToDelete.meets.ToList<CourseMeet>();
actual = target.RemoveCourseConfirmed(courseToDelete);
foreach (var meet in meets)
{
Assert.IsNull(db.Meets.find(meet));
}
Assert.IsNull(db.Courses.Find(courseToDelete.courseID));
}
Which tests the following method from my controller.
[HttpPost, ActionName("RemoveCourse")]
public ActionResult RemoveCourseConfirmed(Course course)
{
try
{
db.Entry(course).State = EntityState.Deleted;
db.SaveChanges();
return RedirectToAction("Index");
}
catch (DbUpdateConcurrencyException)
{
return RedirectToAction("RemoveMeet", new System.Web.Routing.RouteValueDictionary { { "concurrencyError", true } });
}
catch (DataException)
{
ModelState.AddModelError(string.Empty, "Unable to save changes. Try again.");
return View(course);
}
}
I know i should be using a Mock db .... but for this project I have decided to go with this approach.
So this what happens. When I run the actual web site this function works perfectly fine and removes the course and all the meets that belong to it.
But when I run the test i get the following exception
System.InvalidOperationException: The operation failed: The relationship could not be
changed because one or more of the foreign-key properties is non-nullable. When a change is
made to a relationship, the related foreign-key property is set to a null value. If the
foreign-key does not support null values, a new relationship must be defined, the foreign-
key property must be assigned another non-null value, or the unrelated object must be
deleted.
Here is the even more interesting part if I comment out the following line from the test
List<CourseMeet> meets = courseToDelete.meets.ToList<CourseMeet>();
and replace the loop with the following:
foreach (var meet in db.Meets.ToList())
{
Assert.IsFalse(meet.courseID == courseToDelete.courseID);
}
I dont get any exceptions and the test case passess.
Am I missing something about Entity Framework or is this a bug?
Well this has been open for a while now. I still haven't been able to find a definite answer but working more with MVC and EF i think what is happening is that once i execute the line
List<CourseMeet> meets = courseToDelete.meets.ToList<CourseMeet>();
the meets get loaded into the object manager and hence when the parent object is deleted the no longer have a reference to the parent course.