I need to be able to save the same model multiple times in with a for loop. My Action has two parameters, InventoryViewModel movie and int quantity. If the quantity is 3, for example, I need to save three copies to the database.
In my controller I have:
[HttpPost]
public ActionResult addInventory(InventoryViewModel movie, int Quantity)
{
movie.Inventory.isAvail = true;
if (ModelState.IsValid)
{
for (int i = 0; i < Quantity; i++)
{
inventoryRepository.save(movie.Inventory);
movie = new InventoryViewModel();
}
return RedirectToAction("index");
}
return View("index", movie);
}
I thought setting the movie = new InventoryViewModel would create a new instance of the movie, but it doesn't work. If I take that line out, it hits the else statement after it adds the first copy to the database. The CheckoutNum is the primary key of the table so I cannot set it to 0 in the for loop. I can't remember the exact error, but it's something about the primary key cannot be modified.
Repository:
public void save(Inventory movie)
{
if (movie.CheckoutNum == 0)
db.Inventory.Add(movie);
else
db.Entry<Inventory>(movie).State = System.Data.EntityState.Modified;
db.SaveChanges();
}
When you first saved your entity it is already flagged as "not new". So on succeeding calls it will do an update. What you should do is create a new instance of Inventory on each loop:
for (int i = 0; i < Quantity; i++)
{
var entityToSave = new Inventory();
// map the property values to save
inventoryRepository.save(entityToSave);
}
Related
I'm trying to change from SQLite to Realm.io in my Xamarin projects, but can't find any autoincrement on ID's. I found a post with Java, with following line:
int nextID = (int) (realm.where(dbObj.class).maximumInt("id") + 1);
In Xamarin there isn't a where, but i tried this:
realm.All<DebitorPlateDBModel> ().Max (x => x.Id + 1);
Sadly "Max" isn't support.
Has anyone succeed on this?
There are different ways of achieving this, it just depends on what fits your model the best, here are a just a couple:
Test Model:
public class IdIntKeyModel : RealmObject
{
[Indexed]
public int ID { get; set; }
public string Humanized { get; set; }
}
Gap-less key ordering (via Count):
Note: Good for initial bulk imports
Note: Assumes only one thread adding records and you do not have gaps in your record ids, i.e. no deletes without reordering keys, etc...
var config = RealmConfiguration.DefaultConfiguration;
config.SchemaVersion = 1;
using (var theRealm = Realm.GetInstance("StackoverFlow.realm"))
{
var key = theRealm.All<IdIntKeyModel>();
theRealm.Write(() =>
{
for (int i = 1; i < 1000; i++)
{
var model = theRealm.CreateObject<IdIntKeyModel>();
model.ID = key.Count() + 1;
model.Humanized = model.ID.ToWords();
System.Diagnostics.Debug.WriteLine($"{model.ID} : {model.Humanized}");
}
});
var whatIsTheKey = theRealm.All<IdIntKeyModel>().OrderBy(modelKey => modelKey.ID).Last();
System.Diagnostics.Debug.WriteLine($"{whatIsTheKey.ID} : {whatIsTheKey.Humanized}");
}
Gap'ie key ordering (refetch the last record by indexed ID):
Note: "Gap'ie" is Trademark pending ;-)
var rand = new Random();
var config = RealmConfiguration.DefaultConfiguration;
config.SchemaVersion = 1;
using (var theRealm = Realm.GetInstance("StackOverflow.realm"))
{
theRealm.Write(() =>
{
for (int i = 1; i < 1000; i++)
{
var lastID = theRealm.All<IdIntKeyModel>().OrderByDescending(modelKey => modelKey.ID).FirstOrDefault();
var model = theRealm.CreateObject<IdIntKeyModel>();
model.ID = lastID != null ? lastID.ID + rand.Next(10) : 1; // use lastID.ID++ for normal code flow, using rand.Next as a test to check ID indexing
model.Humanized = model.ID.ToWords();
}
});
var lastKey = theRealm.All<IdIntKeyModel>().OrderBy(modelKey => modelKey.ID).Last();
System.Diagnostics.Debug.WriteLine($"{lastKey.ID} : {lastKey.Humanized}");
}
Note: Code updates based on added support for FirstOrDefault, tested w/ v0.78.1
"In Xamarin there isn't a where" is not correct - we support LINQ as you can see in the snippets on the home page.
However, you are correct that we don't (yet) have an auto-increment or anything for that role.
We will get something at some point, but due to synchronisation issues it will not be auto-increment, but rather something like auto-unique-id.
We just released the full Mobile Platform with sync (Xamarin is getting there). One of the big deals of the Realm Object Server is dealing with people who are editing offline data and then having highly reliable synchronisation to other Realms.
There is no way that simple auto-increment can be made to work with disconnected data creation (the first time I dealt with this was on a Mac back in 1996 but the laws of physics haven't changed, we just stopped using floppy disks).
where clause is actually supported by Realm. You only need to import linq. However, auto increment id is really a big deal.
I solved auto increment issue by creating my own id
using Realms;
using System;
namespace RealmDatabase
{
public class RealmUserObject : RealmObject
{
[PrimaryKey]
public int userID { get; set; }
public string userLoginName { get; set; }
public DateTimeOffset userCreated { get; set; }
public bool userActive { get; set; }
}
}
and then when adding account, i'm getting last user info from realm then get the last id from it ( which is int ) then + 1 before to insert new account.
public List<RealmUserObject> getAllUserAccountsFromDatabase()
{
try
{
realm = Realm.GetInstance(config);
return realm.All<RealmUserObject>().Last();
}
catch (Exception) { throw; }
}
i am calling whole account because it is useful for me in other scenario. but you can actually ask directly what you want like this way
return realm.All<RealmUserObject>().Last().userID;
note: ofcourse the issue with this is what if you don't have any record existing, then just insert it and make id initial to 1 and put else if account is greater than 0
I am trying to find a way to improve insert performances with the following code (please, read my questions after the code block):
//Domain classes
[Table("Products")]
public class Product
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
public string Sku { get; set; }
[ForeignKey("Orders")]
public virtual ICollection<Order> Orders { get; set; }
public Product()
{
Orders = new List<Order>();
}
}
[Table("Orders")]
public class Order
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
public string Title { get; set; }
public decimal Total { get; set; }
[ForeignKey("Products")]
public virtual ICollection<Product> Products { get; set; }
public Order()
{
Products = new List<Product>();
}
}
//Data access
public class MyDataContext : DbContext
{
public MyDataContext()
: base("MyDataContext")
{
Configuration.LazyLoadingEnabled = true;
Configuration.ProxyCreationEnabled = true;
Database.SetInitializer(new CreateDatabaseIfNotExists<MyDataContext>());
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Product>().ToTable("Products");
modelBuilder.Entity<Order>().ToTable("Orders");
}
}
//Service layer
public interface IServices<T, K>
{
T Create(T item);
T Read(K key);
IEnumerable<T> ReadAll(Expression<Func<IEnumerable<T>, IEnumerable<T>>> pre);
T Update(T item);
void Delete(K key);
void Save();
void Dispose();
void BatchSave(IEnumerable<T> list);
void BatchUpdate(IEnumerable<T> list, Action<UpdateSpecification<T>> spec);
}
public class BaseServices<T, K> : IDisposable, IServices<T, K> where T : class
{
protected MyDataContext Context;
public BaseServices()
{
Context = new MyDataContext();
}
public T Create(T item)
{
T created;
created = Context.Set<T>().Add(item);
return created;
}
public void Delete(K key)
{
var item = Read(key);
if (item == null)
return;
Context.Set<T>().Attach(item);
Context.Set<T>().Remove(item);
}
public T Read(K key)
{
T read;
read = Context.Set<T>().Find(key);
return read;
}
public IEnumerable<T> ReadAll(Expression<Func<IEnumerable<T>, IEnumerable<T>>> pre)
{
IEnumerable<T> read;
read = Context.Set<T>().ToList();
read = pre.Compile().Invoke(read);
return read;
}
public T Update(T item)
{
Context.Set<T>().Attach(item);
Context.Entry<T>(item).CurrentValues.SetValues(item);
Context.Entry<T>(item).State = System.Data.Entity.EntityState.Modified;
return item;
}
public void Save()
{
Context.SaveChanges();
}
}
public interface IOrderServices : IServices<Order, int>
{
//custom logic goes here
}
public interface IProductServices : IServices<Product, int>
{
//custom logic goes here
}
//Web project's controller
public ActionResult TestCreateProducts()
{
//Create 100 new rest products
for (int i = 0; i < 100; i++)
{
_productServices.Create(new Product
{
Sku = i.ToString()
});
}
_productServices.Save();
var products = _productServices.ReadAll(r => r); //get a list of saved products to add them to orders
var random = new Random();
var orders = new List<Order>();
var count = 0;
//Create 3000 orders
for (int i = 1; i <= 3000; i++)
{
//Generate a random list of products to attach to the current order
var productIds = new List<int>();
var x = random.Next(1, products.Count() - 1);
for (int j = 0; j < x; j++)
{
productIds.Add(random.Next(products.Min(r => r.Id), products.Max(r => r.Id)));
}
//Create the order
var order = new Order
{
Title = "Order" + i,
Total = i,
Products = products.Where(p => productIds.Contains(p.Id))
};
orders.Add(order);
}
_orderServices.CreateRange(orders);
_orderServices.Save();
return RedirectToAction("Index");
}
This code works fine but is very VERY slow when the SaveChanges is executed.
Behind the scene, the annotations on the domain objects creates all the relationships needed: a OrderProducts table with the proper foreign keys are automatically created and the inserts are being done by EF properly.
I've tried many things with bulk inserts using EntityFramework.Utilities, SqlBulkCopy, etc... but none worked.
Is there a way to achieve this?
Understand this is only for testing purposes and my goal is to optimize the best I can any operations in our softwares using EF.
Thanks!
Just before you do your inserts disable your context's AutoDetectChangesEnabled (by setting it to false). Do your inserts and then set the AutoDetectChangesEnabled back to true e.g.;
try
{
MyContext.Configuration.AutoDetectChangesEnabled = false;
// do your inserts updates etc..
}
finally
{
MyContext.Configuration.AutoDetectChangesEnabled = true;
}
You can find more information on what this is doing here
I see two reasons why your code is slow.
Add vs. AddRange
You add entity one by one using the Create method.
You should always use AddRange over Add. The Add method will try to DetectChanges every time the add method is invoked while AddRange only once.
You should add a "CreateRange" method in your code.
public IEnumerable<T> CreateRange(IEnumerable<T> list)
{
return Context.Set<T>().AddRange(list);
}
var products = new List<Product>();
//Create 100 new rest products
for (int i = 0; i < 100; i++)
{
products.Add(new Product { Sku = i.ToString() });
}
_productServices.CreateRange(list);
_productServices.Save();
Disabling / Enabling the property AutoDetectChanges also work as #mark_h proposed, however personally I don't like this kind of solution.
Database Round Trip
A database round trip is required for every record to add, modify or delete. So if you insert 3,000 records, then 3,000 database round trip will be required which is VERY slow.
You already tried EntityFramework.BulkInsert or SqlBulkCopy, which is great. I recommend you first to try them again using the "AddRange" fix to see the newly performance.
Here is a biased comparison of library supporting BulkInsert for EF:
Entity Framework - Bulk Insert Library Reviews & Comparisons
Disclaimer: I'm the owner of the project Entity Framework Extensions
This library allows you to BulkSaveChanges, BulkInsert, BulkUpdate, BulkDelete and BulkMerge within your Database.
It supports all inheritances and associations.
// Easy to use
public void Save()
{
// Context.SaveChanges();
Context.BulkSaveChanges();
}
// Easy to customize
public void Save()
{
// Context.SaveChanges();
Context.BulkSaveChanges(bulk => bulk.BatchSize = 100);
}
EDIT: Added answer to sub question
An entity object cannot be referenced by multiple instances of
IEntityChangeTracker
The issue happens because you use two different DbContext. One for the product and one for order.
You may find a better answer than mine in a different thread like this answer.
The Add method successfully attach the product, subsequent call of the same product doesn't throw an error because it's the same product.
The AddRange method, however, attach the product multiple time since it's not come from the same context, so when Detect Changes is called, he doesn't know how to handle it.
One way to fix it is by re-using the same context
var _productServices = new BaseServices<Product, int>();
var _orderServices = new BaseServices<Order, int>(_productServices.Context);
While it may not be elegant, the performance will be improved.
I have problem regarding my Filtering of my Table. I'm using a ViewerFilter and override the select Method to fitler that Table. The Filtertext itself is entered via a Textfield.
So now to my problem. For example my table looks like the following:
column
123
124
In my textfield the user can enter the columnname=data1,data2 to show all rows which have either data1 or data2 as data. so in my above example if the user enters column=123,124 both rows should still be visible. The problem here is that I refresh my tableviewer after each entered character. So when the user enters column=123 the Table only shows one column. When adding ,124 to the filtertext I filter my already filtered table. So no data gets shown at the end. How can I still filter the original Tabledata?
#Override
public boolean select(final Viewer viewer, final Object parentElement, final Object element) {
final String filterString = filterText.getText().toLowerCase();
if (filterString.length() == 0) { return true; }
final mydata myData= (mydata) element;
if (filterString.matches("columnName" + ".+")) {
index = filterString.indexOf("columnName" + ".+");
evaluateText(myData, filterString, i, index + tableColumnsText[i].length())
}
public boolean evaluateText(final mydata data, final String filterText, final int beginningIndex) {
subString = filterText.substring(beginningIndex, filterText.length());
return evaluateString(data.getString(), subString);
}
public boolean evaluateString(final String cellString, final String commaString) {
int countSubstrings = 0;
final String[] items = commaString.split(",");
countSubstrings = items.length;
for (final String s : items) {
if (s.length() != 0) {
if (!cellString.contains(s)) { return false; }
}
}
return true;
}
So I tried to filter out the main components of the method. Can I somehow access the unfiltered table?
I have 5 records coming from a simple select stored procedure.
ID Name
1 RecordOne
2 RecordTwo
3 RecordThree
4 RecordFour
5. RecordFive
Requirement is to display one record at a time example:
Record One
Previous Next
Two Action links or buttons with Previous and Next text.
If user clicks Next user will see
RecordTwo
and so on,same for previous case.
My model
namespace MVCLearning.Models
{
public class VMNews
{
public List<Student> StudentDetails { get; set; }
}
public class Student
{
public int ID { get; set; }
public string Name { get; set; }
}
}
Action
public ActionResult Index()
{
VMNews objnews = new VMNews();
objnews.StudentDetails = db.Database.SqlQuery<Student>("usp_studentdetails").ToList();
return View(objnews);
}
View
<div>
#foreach (var item in Model.SD.Take(1))
{
<h3>#item.Name</h3>
<h3>#item.Age</h3>
}
#Html.ActionLink("Next", "index", new { Model.SD[0].ID})
#Html.ActionLink("Previous", "index", new { Model.SD[0].ID })
The way I have written the view is totally wrong am not getting how and what to write on the action and what to write on the View.
What will be one of the way to achieve this.
Change you method to
public ActionResult Index(int? index)
{
int max = 5; // modify based on the actual number of records
int currentIndex = index.GetValueOrDefault();
if (currentIndex == 0)
{
ViewBag.NextIndex = 1;
}
else if (currentIndex >= max)
{
currentIndex = max;
ViewBag.PreviousIndex = currentIndex - 1;
}
else
{
ViewBag.PreviousIndex = currentIndex - 1;
ViewBag.NextIndex = currentIndex + 1;
}
VMNews objnews = new VMNews();
Student model = db.Database.SqlQuery<Student>("usp_studentdetails")
.Skip(currentIndex).Take(1).FirstOrDefault();
return View(model);
}
Note that the query has been modified to return only one Student since that is all that you require in the view. Also I have asssumed if a user enters a value greater than the number of records it will return the last record (you may in fact want to throw an error?)
The view now needs to be
#model Student
<h3>#Model.Name</h3>
<h3>#Model.Age</h3>
#if (ViewBag.PreviousIndex != null)
{
#Html.ActionLink("Previous", "Index", new { index = ViewBag.PreviousIndex })
}
#if (ViewBag.NextIndex != null)
{
#Html.ActionLink("Next", "Index", new { index = ViewBag.NextIndex })
}
I have this two objects - Magazine and Author (M-M relationship):
public partial class MAGAZINE
{
public MAGAZINE()
{
this.AUTHORs = new HashSet<AUTHOR>();
}
public long REF_ID { get; set; }
public string NOTES { get; set; }
public string TITLE { get; set; }
public virtual REFERENCE REFERENCE { get; set; }
public virtual ICollection<AUTHOR> AUTHORs { get; set; }
}
public partial class AUTHOR
{
public AUTHOR()
{
this.MAGAZINEs = new HashSet<MAGAZINE>();
}
public long AUTHOR_ID { get; set; }
public string FULL_NAME { get; set; }
public virtual ICollection<MAGAZINE> MAGAZINEs { get; set; }
}
}
My problem is that I can't seem to update the number of authors against a magazine e.g. if I have 1 author called "Smith, P." stored already against a magazine, I can add another called "Jones, D.", but after the post back to the Edit controller the number of authors still shows 1 - i.e. "Smith, P.H".
Please not that I have successfully model bound the number of authors back to the parent entity (Magazine), it uses a custom model binder to retrieve the authors and bind to the Magazine (I think), but it still doesn't seem to update properly.
My code for updating the model is straight forward - and shows the variable values both before and after:
public ActionResult Edit(long id)
{
MAGAZINE magazine = db.MAGAZINEs.Find(id);
return View(magazine);
}
and here are the variables pre-editing/updating -
[HttpPost]
public ActionResult Edit(MAGAZINE magazine)
{
if (ModelState.IsValid)
{
db.Entry(magazine).State = EntityState.Modified;
db.SaveChanges();
return RedirectToAction("Index");
}
return View(magazine);
}
...and here are the variables after a new author has been added...
I am getting suspicious that the author entity is showing, post edit that it is not bound to any magazine and I am guessing this is why it is not being updated back to the magazine entity - but it is perplexing as I am effectively dealing with the same magazine entity - I guess it may be something to do with the custom model binder for the author.
Can anyone help on this matter?
For completeness - I have included my AuthorModelBinder class too -
public class AuthorModelBinder : IModelBinder
{
public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
var values = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
if (values != null)
{
// We have specified asterisk (*) as a token delimiter. So
// the ids will be separated by *. For example "2*3*5"
var ids = values.AttemptedValue.Split('*');
List<int> validIds = new List<int>();
foreach (string id in ids)
{
int successInt;
if (int.TryParse(id, out successInt))
{
validIds.Add(successInt);
}
else
{
//Make a new author
AUTHOR author = new AUTHOR();
author.FULL_NAME = id.Replace("\'", "").Trim();
using (RefmanEntities db = new RefmanEntities())
{
db.AUTHORs.Add(author);
db.SaveChanges();
validIds.Add((int)author.AUTHOR_ID);
}
}
}
//Now that we have the selected ids we could fetch the corresponding
//authors from our datasource
var authors = AuthorController.GetAllAuthors().Where(x => validIds.Contains((int)x.Key)).Select(x => new AUTHOR
{
AUTHOR_ID = x.Key,
FULL_NAME = x.Value
}).ToList();
return authors;
}
return Enumerable.Empty<AUTHOR>();
}
}
I faced a very similar scenario when I developed my blog using MVC/Nhibernate and the entities are Post and Tag.
I too had an edit action something like this,
public ActionResult Edit(Post post)
{
if (ModelState.IsValid)
{
repo.EditPost(post);
...
}
...
}
But unlike you I've created a custom model binder for the Post not Tag. In the custom PostModelBinder I'm doing pretty much samething what you are doing there (but I'm not creating new Tags as you are doing for Authors). Basically I created a new Post instance populating all it's properties from the POSTed form and getting all the Tags for the ids from the database. Note that, I only fetched the Tags from the database not the Post.
I may suggest you to create a ModelBinder for the Magazine and check it out. Also it's better to use repository pattern instead of directly making the calls from controllers.
UPDATE:
Here is the complete source code of the Post model binder
namespace PrideParrot.Web.Controllers.ModelBinders
{
[ValidateInput(false)]
public class PostBinder : IModelBinder
{
private IRepository repo;
public PostBinder(IRepository repo)
{
this.repo = repo;
}
#region IModelBinder Members
public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
{
HttpRequestBase request = controllerContext.HttpContext.Request;
// retrieving the posted values.
string oper = request.Form.Get("oper"),
idStr = request.Form.Get("Id"),
heading = request.Form.Get("Heading"),
description = request.Form.Get("Description"),
tagsStr = request.Form.Get("Tags"),
postTypeIdStr = request.Form.Get("PostType"),
postedDateStr = request.Form.Get("PostedDate"),
isPublishedStr = request.Form.Get("Published"),
fileName = request.Form.Get("FileName"),
serialNoStr = request.Form.Get("SerialNo"),
metaTags = request.Form.Get("MetaTags"),
metaDescription = request.Form.Get("MetaDescription"),
themeIdStr = request.Form.Get("Theme");
// initializing to default values.
int id = 0, serialNo = 0;
DateTime postedDate = DateTime.UtcNow;
DateTime? modifiedDate = DateTime.UtcNow;
postedDate.AddMilliseconds(-postedDate.Millisecond);
modifiedDate.Value.AddMilliseconds(-modifiedDate.Value.Millisecond);
/*if operation is not specified throw exception.
operation should be either'add' or 'edit'*/
if (string.IsNullOrEmpty(oper))
throw new Exception("Operation not specified");
// if there is no 'id' in edit operation add error to model.
if (string.IsNullOrEmpty(idStr) || idStr.Equals("_empty"))
{
if (oper.Equals("edit"))
bindingContext.ModelState.AddModelError("Id", "Id is empty");
}
else
id = int.Parse(idStr);
// check if heading is not empty.
if (string.IsNullOrEmpty(heading))
bindingContext.ModelState.AddModelError("Heading", "Heading: Field is required");
else if (heading.Length > 500)
bindingContext.ModelState.AddModelError("HeadingLength", "Heading: Length should not be greater than 500 characters");
// check if description is not empty.
if (string.IsNullOrEmpty(description))
bindingContext.ModelState.AddModelError("Description", "Description: Field is required");
// check if tags is not empty.
if (string.IsNullOrEmpty(metaTags))
bindingContext.ModelState.AddModelError("Tags", "Tags: Field is required");
else if (metaTags.Length > 500)
bindingContext.ModelState.AddModelError("TagsLength", "Tags: Length should not be greater than 500 characters");
// check if metadescription is not empty.
if (string.IsNullOrEmpty(metaTags))
bindingContext.ModelState.AddModelError("MetaDescription", "Meta Description: Field is required");
else if (metaTags.Length > 500)
bindingContext.ModelState.AddModelError("MetaDescription", "Meta Description: Length should not be greater than 500 characters");
// check if file name is not empty.
if (string.IsNullOrEmpty(fileName))
bindingContext.ModelState.AddModelError("FileName", "File Name: Field is required");
else if (fileName.Length > 50)
bindingContext.ModelState.AddModelError("FileNameLength", "FileName: Length should not be greater than 50 characters");
bool isPublished = !string.IsNullOrEmpty(isPublishedStr) ? Convert.ToBoolean(isPublishedStr.ToString()) : false;
//** TAGS
var tags = new List<PostTag>();
var tagIds = tagsStr.Split(',');
foreach (var tagId in tagIds)
{
tags.Add(repo.PostTag(int.Parse(tagId)));
}
if(tags.Count == 0)
bindingContext.ModelState.AddModelError("Tags", "Tags: The Post should have atleast one tag");
// retrieving the post type from repository.
int postTypeId = !string.IsNullOrEmpty(postTypeIdStr) ? int.Parse(postTypeIdStr) : 0;
var postType = repo.PostType(postTypeId);
if (postType == null)
bindingContext.ModelState.AddModelError("PostType", "Post Type is null");
Theme theme = null;
if (!string.IsNullOrEmpty(themeIdStr))
theme = repo.Theme(int.Parse(themeIdStr));
// serial no
if (oper.Equals("edit"))
{
if (string.IsNullOrEmpty(serialNoStr))
bindingContext.ModelState.AddModelError("SerialNo", "Serial No is empty");
else
serialNo = int.Parse(serialNoStr);
}
else
{
serialNo = repo.TotalPosts(false) + 1;
}
// check if commented date is not empty in edit.
if (string.IsNullOrEmpty(postedDateStr))
{
if (oper.Equals("edit"))
bindingContext.ModelState.AddModelError("PostedDate", "Posted Date is empty");
}
else
postedDate = Convert.ToDateTime(postedDateStr.ToString());
// CREATE NEW POST INSTANCE
return new Post
{
Id = id,
Heading = heading,
Description = description,
MetaTags = metaTags,
MetaDescription = metaDescription,
Tags = tags,
PostType = postType,
PostedDate = postedDate,
ModifiedDate = oper.Equals("edit") ? modifiedDate : null,
Published = isPublished,
FileName = fileName,
SerialNo = serialNo,
Theme = theme
};
}
#endregion
}
}
This line db.Entry(magazine).State = EntityState.Modified; only tells EF that magazine entity has changed. It says nothing about relations. If you call Attach all entities in object graph are attached in Unchanged state and you must handle each of them separately. What is even worse in case of many-to-many relation you must also handle relation itself (and changing state of relation in DbContext API is not possible).
I spent a lot of time with this problem and design in disconnected app. And there are three general approaches:
You will send additional information with your entities to find what has changed and what has been deleted (yes you need to track deleted items or relations as well). Then you will manually set state of every entity and relation in object graph.
You will just use data you have at the moment but instead of attaching them to the context you will load current magazine and every author you need and reconstruct those changes on those loaded entities.
You will not do this at all and instead use lightweight AJAX calls to add or remove every single author. I found this common for many complex UIs.