EntityValidationErrors Reporting Incorrectly - c#

I have a case where entities.SaveChanges() is throwing a DbEntityValidationException and stating
The AValue field is required", however the AValue property has been populated.
Is there something else that can be checked to determine why this is throwing this error.
The basic code throwing the error:
try
{
var entities = new MyEntities();
var item = (from i in entities.Item
where i.Id == 1
select i).First();
item.AValue = "NewValue";
entities.SaveChanges();
}
catch (DbEntityValidationException exception)
{
var report = exception.Message();
}
I've done a bit of digging and in the catch have put:
var x = item.AValue; // and it shows "NewValue"
and
var message = new StringBuilder();
foreach (var entityValidationError in exception.EntityValidationErrors)
{
foreach (var validationError in entityValidationError.ValidationErrors)
{
object value = null;
try { value = entityValidationError.Entry.CurrentValues.GetValue<object>(validationError.PropertyName); }
catch (System.Exception exception) { value = null; }
message.AppendLine(validationError.PropertyName + ": " + validationError.ErrorMessage + " (VALUE: " + (value ?? "-") + ")");
}
}
return message.ToString();
// and i get "AValue: The AValue field is required. (VALUE: -) so that value item is null
I'm pretty stumped at this point, just can't figure out why it looks fine during the try but still throws a validation error message. Is there anything else I can add to see if there is something else going on there? Or any other recommended troubleshooting steps?


Please verify that the Item.AValue is set up properly in the Entity Framework dataset definition so that it is pointing to the AValue column in the relevant database table. If for some reason this is missing, then setting it in code would not cause it to be updated in the Db, which could lead to this error.


Your code contains some small syntax mistakes:
var item = (from i in entities.Item
where i.Id = 1
select i).First();
should be (double == sign)
var item = (from i in entities.Item
where i.Id == 1
select i).First();
Also:
item.AValue = "NewValue"
should be followed by a ";" sign.
I've recreated a small example that works:
Object class:
public class Item
{
[Key]
public int Id { get; set; }
[Required]
public string Name { get; set; }
}
Entity Framework context class:
public class Context : DbContext
{
public DbSet<Item> items { get; set; }
public Context()
: base("Demo")
{
}
}
On the first run, adds an item in the database:
using (var ctx = new Context())
{
Item stud = new Item() { Name = "Name" };
ctx.items.Add(stud);
ctx.SaveChanges();
}
Now, replace the code above with the following code:
try
{
var entities = new Context();
var item = (from i in entities.items
where i.Id == 1
select i).First();
item.Name = "NewValue";
entities.SaveChanges();
}
catch (DbEntityValidationException exception)
{
}


It seems that the issue was that there was a sub-object on my item that also had a property of AValue and this was the one that was throwing the exception.
Is there some way (via the DbEntityValidationException) to report on what object it is as well?

Related

Finding if a property inside a list inside a list doesnt contain a specific string

I have a huge product database im working with threw a api
The API returns a Product those Products have MetaData which are stuff like minQuantities Maxes ect
Now I noticed some products dont have "variation_maximum_allowed_quantity" or " maximum_allowed_quantity"
So for every Product I have to look threw That Products meta data to so something like
foreach (var item in VarProduct)
{
foreach (var metaItem in item.meta_data)
{
}
}
The issue is meta_data have Key's Id's and value's I need to check against every key inside of every meta_data inside of every Product if that makes sense? Im wrecking my brain atm, Anyone know how I can check against all of those to see if those 2 Strings are missing? I need to be able to do something like
if(mdDoesntcontain)
{
//This means stock is Unlimiteed so need to set a value for stock
item.stockquantity = 9999999; (or int.maxValue())
}
Little tricky Posting this as a Block but:
-item.meta_data count = w.e
-[0]
-base
-id = 101231
-key = "min_max_rules"
-value = "no"
-[1]
-base
-id = 123131
-key = "variation_minimum_allowed_quantity"
-value = ""(this means 1 usually)
public class MetaData
{
private object preValue;
[DataMember (EmitDefaultValue = false)]
public int? id {
get;
set;
}
[DataMember (EmitDefaultValue = false)]
public string key {
get;
set;
}
[DataMember (EmitDefaultValue = false)]
public object value {
get;
set;
}

foreach (var item in VarProduct)
{
hasQuantity = false;
foreach (var metaItem in item.meta_data)
{
if (metaItem.id == "variation_maximum_allowed_quantity" || metaItem.id == "maximum_allowed_quantity") {
hasQuantity = true;
break;
}
}
if (!hasQuantity) {
item.stockQuantity = int.MaxValue;
}
}

Would this be the solution you're looking for?
foreach (var item in VarProduct)
{
var hasQuantity = false;
foreach (var metaItem in item.meta_data)
{
if (metaItem.key == "variation_maximum_allowed_quantity" || metaItem.key == "maximum_allowed_quantity") {
item.stockQuantity = metaItem.value == "" ? 1 : int.Parse(metaItem.value);
hasQuantity = true;
break;
}
}
if(!hasQuantity) {
item.stockQuantity = int.MaxValue;
}
}

You could use linq Any operation:
foreach (var item in VarProduct)
{
if (!item.meta_data.Any(m => m.key.Equals("variation_maximum_allowed_quantity")
|| m.key.Equals("maximum_allowed_quantity")))
{
item.stockQuantity = int.MaxValue;
}
}

Get the largest Value from table unless null

I'm quite new to C# and ASP.NET (and programming in general) and try to do some simple exercises.
What I am trying to do:
I would like to build a simple MVC App where records will have versions.
That is: Given a record, that I am about to change via the "Edit"-View, this record will not be overwritten. Instead a new record will be created (like a new Version). Both, the old and new record, have the same ItemId (which is not the primary key!), that links them together "semantically". In order to know, which record is the newer Version, the newer record has a VersionId that is +1 the VersionId of the older one.
Currently: I've started working on the Create-Action. A new record shall get a value of 1 for it's VersionId and for ItemId the largest ItemId already in the DB plus 1 - unless there is no record in the DB in which case ItemId shall be 1.
The Model:
namespace HowToUpdate.Models
{
public class ItemWithVersion
{
public int Id { get; set; }
public int ItemNr { get; set; }
public int VersionNr { get; set; }
public string Name { get; set; }
}
}
The Controller Action:
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Create([Bind(Include = "Id,Name")] ItemWithVersion itemWithVersion)
{
if (ModelState.IsValid)
{
// set the ItemNr
int currentMaxItemNr = db.ItemWithVersions.Max(i => i.ItemNr);
itemWithVersion.ItemNr = currentMaxItemNr + 1;
// set the VersionNr
itemWithVersion.VersionNr = 1;
db.ItemWithVersions.Add(itemWithVersion);
db.SaveChanges();
return RedirectToAction("Index");
}
return View(itemWithVersion);
}
Problem: When I run localhost/ItemWithVersion/Create, enter a Value for the Name and Submit, i get the following error:
"The cast to value type 'System.Int32' failed because the materialized value is null. Either the result type's generic parameter or the query must use a nullable type.
Source error: int currentMaxItemNr = db.ItemWithVersions.Max(i => i.ItemNr);"
I tried:
// set the ItemNr
int currentMaxItemNr = db.ItemWithVersions.Max(i => i.ItemNr);
if (currentMaxItemNr == null)
{
itemWithVersion.ItemNr = 1;
}
else
{
itemWithVersion.ItemNr = currentMaxItemNr + 1;
}
Now the error seems to be int currentMaxItemNr = db.ItemWithVersions.Max(i => i.ItemNr);
Also int? currentMaxItemNr = db.ItemWithVersions.Max(i => i.ItemNr); and var currentMaxItemNr = db.ItemWithVersions.Max(i => i.ItemNr); won't do any good.
It's probably basic but I need your help! :) Thx.

Your if-statement is wrong:
if (currentMaxItemNr != null)
currently checks if currentMaxItemNr has a value and if it does, make it 1
So your statement should be if (currentMaxItemNr == null)
Edit:
I can't replicate your error unfortunately, but I did check and found out that there's an exception thrown when calling Max() on an empty List. So it would be better to first call if (db.ItemWithVersions.Count() > 0)
That way you are sure that Max() will return a result. If it fails that statement, you can set currentMaxItemNr to 0

You need to make sure that your table is not empty before calling the Max() method. You can use the Any() method to do that.
int currentMaxItemNr = 0;
if (db.ItemWithVersions.Any())
{
currentMaxItemNr = db.ItemWithVersions.Max(i => i.ItemNr);
}
itemWithVersion.ItemNr = currentMaxItemNr + 1;
// set the VersionNr
itemWithVersion.VersionNr = 1;
db.ItemWithVersions.Add(itemWithVersion);
db.SaveChanges();

Probably, the reason is that Id is declared as a int (not nullable, so null can not be assigned to id) . Try following.
public int? Id { get; set; }

Care to try?
int currentMaxItemNr = db.ItemWithVersions.Max(i => i.ItemNr ?? 1);
This will return currentMaxItemNr = 1 if your i.ItemNr is null.

here is how I would do this. When you click on Edit we run:
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Create([Bind(Include = "Id,Name")] ItemWithVersion itemWithVersion)
{
if (ModelState.IsValid)
{
// get the item with highest version
ItemWithVersion item = db.ItemWithVersions.Where(i =>i.ItemNr == itemWithVersion.ItemNr).OrderByDescending(i => i.VersionNr).FirstOrDefault();
//if item doesnt exist we need to create
if(item == null) {
//get the last item with highest ItemNr
ItemWithVersion lastitem = db.ItemWithVersions.OrderByDescending(i => i.ItemNr).FirstOrDefault();
if(lastitem == null) {
//if we didnt find a item, it means is the first item in the DB
itemWithVersion.ItemNr = 1;
} else {
//increment the itemNr for the new Item
itemWithVersion.ItemNr = lastitem.ItemNr + 1;
}
//set version to 1 since is the first version for this new ItemNr
itemWithVersion.VersionNr = 1;
} else {
//if we found a item for the current ItemNr we increase the version for the new item
itemWithVersion.VersionNr = item.VersionNr + 1;
}
db.ItemWithVersions.Add(itemWithVersion);
db.SaveChanges();
return RedirectToAction("Index");
}
return View(itemWithVersion);
}

ArgumentException: This object does not have a Name property

I encountered this error:
This object does not have a Name property, please use the other
contructor.
I am calling data from a WCF to populate a listview. I don't completely understand the error or why it is happening?
WPF
public async Task LoadTrucks()
{
TruckServiceClient TSC = new TruckServiceClient();
try
{
var trucks = await TSC.GetTrucksAsync();
foreach (var truck in trucks)
lbTrucks.Items.Add(new ListBoxViewItem<RTrucks>(truck));
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
WCF
public List<RTrucks> GetTrucks()
{
List<RTrucks> r = new List<RTrucks>();
List<RTrucks> e;
using (TruckDb db = new TruckDb())
{
e = db.RTrucks.Where(x => x.Id != null).ToList();
foreach (var a in e)
{
var truck = new RTrucks()
{
Id = a.Id,
ChassisManufacturer = a.ChassisManufacturer,
ChassisModel = a.ChassisModel,
PhaseId = a.PhaseId,
PhaseStatusId = a.PhaseStatusId,
QuoteId = a.QuoteId
};
r.Add(truck);
}
return r;
}
}

The list view throws this exception because you are trying to add an instance of the following class to the list view, and that class does not have a a Name property
ListBoxViewItem<RTrucks>
Please add the following property to your ListBoxViewItem class and set it's value in the constructor by using either Id or other properties of the truck instance passed in:
public class ListBoxViewItem<T>
{
public string Name { get; set; }
public ListBoxViewItem(T tInstance)
{
.... // current implementation
Name = <set the name using tInstance>;
}
}

Ensure that explicitly set primary key values are unique

I am getting following exception on my project:
An exception of type 'System.InvalidOperationException' occurred in
EntityFramework.dll but was not handled in user code
Additional information: Saving or accepting changes failed because of
more than one entity of type 'MyProject.Data.Poco.MyProjectCountry' have the
same primary key value. Ensure that explicitly set primary key values
are unique. Ensure that database-generated primary keys are configured
correctly in the database and in the Entity Framework model. Use the
Entity Designer for Database First/Model First configuration. Use the
'HasDatabaseGeneratedOption" fluent API or
'DatabaseGeneratedAttribute' for Code First configuration.
the error happens at the following line:
using (MyProjectDataContext context = new MyProjectDataContext())
{
MyProjectItemTag existingItemTag = (from p in context.ItemTags.Include(p => p.MyProjectGenre).Include(p => p.MyProjectCountry)
where p.MyProjectUser.UserId == ItemTag.MyProjectUser.UserId &&
p.MyProjectItem.ItemId == MyProjectItem.ItemId
select p).FirstOrDefault();
// new tag
if (existingItemTag == null)
{
existingItemTag = ItemTag;
existingItemTag.MyProjectItem.ItemId = MyProjectItem.ItemId;
}
// existing tag
else
{
existingItemTag.MyProjectItem = new MyProjectItem { ItemId = MyProjectItem.ItemId };
existingItemTag.MyProjectUser = new MyProjectUser { UserId = ItemTag.MyProjectUser.UserId };
}
// updates
existingItemTag.MyProjectCountry = MyProjectCountry;
if (MyProjectCountry != null)
existingItemTag.MyProjectCountry = new MyProjectCountry()
{
MyProjectCountryId = MyProjectCountry.MyProjectCountryId
};
existingItemTag.MyProjectGenre = MyProjectGenre;
context.Entry(existingItemTag.MyProjectItem).State = EntityState.Unchanged;
context.Entry(existingItemTag.MyProjectUser).State = EntityState.Unchanged;
context.Entry(existingItemTag.MyProjectCountry).State = EntityState.Unchanged;
context.Entry(existingItemTag.MyProjectGenre).State = EntityState.Unchanged;
if (existingItemTag.MyProjectCountry != null)
{
context.Entry(existingItemTag.MyProjectCountry).State = EntityState.Unchanged;
}
// db
context.ItemTags.AddOrUpdate(existingItemTag);
context.SaveChanges();
return existingItemTag.ItemTagId;
}
context.Entry(existingItemTag.MyProjectCountry).State = EntityState.Unchanged;
My Class:
public class MyProjectItemTag
{
public int ItemTagId { get; set; }
public MyProjectUser MyProjectUser { get; set; }
public MyProjectItem MyProjectItem { get; set; }
public MyProjectCountry MyProjectCountry { get; set; }
public MyProjectGenre MyProjectGenre { get; set; }
public MyProjectMood MyProjectMood { get; set; }
public MyProjectItemTag()
{
}
public MyProjectItemTag(string userId, string providerContentId)
{
MyProjectUser = new MyProjectUser
{
UserId = userId
};
MyProjectItem = new MyProjectItem
{
ProviderContentId = providerContentId
};
}
}
My Config:
public class MyProjectItemTagConfiguration : EntityTypeConfiguration<MyProjectItemTag>
{
public MyProjectItemTagConfiguration()
{
ToTable("MyProjectItemTags");
HasKey(p => p.ItemTagId);
HasRequired(p => p.MyProjectUser);
HasRequired(p => p.MyProjectItem);
HasOptional(p => p.MyProjectCountry);
}
}
What I am missing here?

This is all you really need to look for:
Additional information: Saving or accepting changes failed because more than one entity of type 'MyProject.Data.Poco.MyProjectCountry' have the same primary key value.
The following code may not necessarily populate the MyProjectCountry.
MyProjectItemTag existingItemTag =
(from p in context.ItemTags
.Include(p => p.MyProjectGenre)
.Include(p => p.MyProjectCountry)
where p.MyProjectUser.UserId == ItemTag.MyProjectUser.UserId
&& p.MyProjectItem.ItemId == MyProjectItem.ItemId
select p).FirstOrDefault();
So you set it to some variable you haven't give us any context too...
existingItemTag.MyProjectCountry = MyProjectCountry;
I'd assume it is not null, so you change it's ID which is a Giant Code Smell...
(Why assign it? after all it's already assigned..)
if (MyProjectCountry != null)
existingItemTag.MyProjectCountry = new MyProjectCountry()
{
MyProjectCountryId = MyProjectCountry.MyProjectCountryId
};
Then you tell EF it hasn't changed?? Another Code Smell.
context.Entry(existingItemTag.MyProjectCountry).State = EntityState.Unchanged;
So what this tells me is that the Context has already downloaded this entity into its Object Cache, but the one you are assigning is not the one in the cache so when I tries to added to the cache, there is a duplicate.

Try to use context.Model.AddORUpdate(model) Method, you need to add using System.Data.Entity.Migrations as well for this method.

Check in the.edmx file StoreGeneratedPattern. If the Id in the database is auto generated, StoreGeneratedPattern has to be Identity. In my case was None. It's not the best practice to edit the edmx file. I personally deleted the table in the edmx file, I created a new one and after that the StoreGeneratedPattern = Identity.

Validation failed for one or more entities while saving changes to SQL Server Database using Entity Framework

I want to save my Edit to Database and I am using Entity FrameWork Code-First in ASP.NET MVC 3 / C# but I am getting errors. In my Event class, I have DateTime and TimeSpan datatypes but in my database, I've got Date and time respectively. Could this be the reason? How can I cast to the appropriate datatype in the code before saving changes to database.
public class Event
{
public int EventId { get; set; }
public int CategoryId { get; set; }
public int PlaceId { get; set; }
public string Title { get; set; }
public decimal Price { get; set; }
public DateTime EventDate { get; set; }
public TimeSpan StartTime { get; set; }
public TimeSpan EndTime { get; set; }
public string Description { get; set; }
public string EventPlaceUrl { get; set; }
public Category Category { get; set; }
public Place Place { get; set; }
}
Method in the controller >>>> Problem at storeDB.SaveChanges();
// POST: /EventManager/Edit/386
[HttpPost]
public ActionResult Edit(int id, FormCollection collection)
{
var theEvent = storeDB.Events.Find(id);
if (TryUpdateModel(theEvent))
{
storeDB.SaveChanges();
return RedirectToAction("Index");
}
else
{
ViewBag.Categories = storeDB.Categories.OrderBy(g => g.Name).ToList();
ViewBag.Places = storeDB.Places.OrderBy(a => a.Name).ToList();
return View(theEvent);
}
}
with
public class EventCalendarEntities : DbContext
{
public DbSet<Event> Events { get; set; }
public DbSet<Category> Categories { get; set; }
public DbSet<Place> Places { get; set; }
}
SQL Server 2008 R2 Database / T-SQL
EventDate (Datatype = date)
StartTime (Datatype = time)
EndTime (Datatype = time)
Http Form
EventDate (Datatype = DateTime) e.g. 4/8/2011 12:00:00 AM
StartTime (Datatype = Timespan/time not sure) e.g. 08:30:00
EndTime (Datatype = Timespan/time not sure) e.g. 09:00:00
Server Error in '/' Application.
Validation failed for one or more entities. See 'EntityValidationErrors' property for more details.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: System.Data.Entity.Validation.DbEntityValidationException: Validation failed for one or more entities. See 'EntityValidationErrors' property for more details.
Source Error:
Line 75: if (TryUpdateModel(theEvent))
Line 76: {
Line 77: storeDB.SaveChanges();
Line 78: return RedirectToAction("Index");
Line 79: }
Source File: C:\sep\MvcEventCalendar\MvcEventCalendar\Controllers\EventManagerController.cs Line: 77
Stack Trace:
[DbEntityValidationException: Validation failed for one or more entities. See 'EntityValidationErrors' property for more details.]

You can extract all the information from the DbEntityValidationException with the following code (you need to add the namespaces: System.Data.Entity.Validation and System.Diagnostics to your using list):
catch (DbEntityValidationException dbEx)
{
foreach (var validationErrors in dbEx.EntityValidationErrors)
{
foreach (var validationError in validationErrors.ValidationErrors)
{
Trace.TraceInformation("Property: {0} Error: {1}",
validationError.PropertyName,
validationError.ErrorMessage);
}
}
}

No code change required:
While you are in debug mode within the catch {...} block open up the "QuickWatch" window (Ctrl+Alt+Q) and paste in there:
((System.Data.Entity.Validation.DbEntityValidationException)ex).EntityValidationErrors
or:
((System.Data.Entity.Validation.DbEntityValidationException)$exception).EntityValidationErrors
If you are not in a try/catch or don't have access to the exception object.
This will allow you to drill down into the ValidationErrors tree. It's the easiest way I've found to get instant insight into these errors.

In the case you have classes with same property names, here is a small extension to Praveen's answer:
catch (DbEntityValidationException dbEx)
{
foreach (var validationErrors in dbEx.EntityValidationErrors)
{
foreach (var validationError in validationErrors.ValidationErrors)
{
Trace.TraceInformation(
"Class: {0}, Property: {1}, Error: {2}",
validationErrors.Entry.Entity.GetType().FullName,
validationError.PropertyName,
validationError.ErrorMessage);
}
}
}

As an improvement to both Praveen and Tony, I use an override:
public partial class MyDatabaseEntities : DbContext
{
public override int SaveChanges()
{
try
{
return base.SaveChanges();
}
catch (DbEntityValidationException dbEx)
{
foreach (var validationErrors in dbEx.EntityValidationErrors)
{
foreach (var validationError in validationErrors.ValidationErrors)
{
Trace.TraceInformation("Class: {0}, Property: {1}, Error: {2}",
validationErrors.Entry.Entity.GetType().FullName,
validationError.PropertyName,
validationError.ErrorMessage);
}
}
throw; // You can also choose to handle the exception here...
}
}
}

This implementation wrap entity exception to exception with detail text.
It handles DbEntityValidationException, DbUpdateException, datetime2 range errors (MS SQL), and include key of invalid entity in message (useful when savind many entities at one SaveChanges call).
First, override SaveChanges in DbContext class:
public class AppDbContext : DbContext
{
public override int SaveChanges()
{
try
{
return base.SaveChanges();
}
catch (DbEntityValidationException dbEntityValidationException)
{
throw ExceptionHelper.CreateFromEntityValidation(dbEntityValidationException);
}
catch (DbUpdateException dbUpdateException)
{
throw ExceptionHelper.CreateFromDbUpdateException(dbUpdateException);
}
}
public override async Task<int> SaveChangesAsync(CancellationToken cancellationToken)
{
try
{
return await base.SaveChangesAsync(cancellationToken);
}
catch (DbEntityValidationException dbEntityValidationException)
{
throw ExceptionHelper.CreateFromEntityValidation(dbEntityValidationException);
}
catch (DbUpdateException dbUpdateException)
{
throw ExceptionHelper.CreateFromDbUpdateException(dbUpdateException);
}
}
ExceptionHelper class:
public class ExceptionHelper
{
public static Exception CreateFromEntityValidation(DbEntityValidationException ex)
{
return new Exception(GetDbEntityValidationMessage(ex), ex);
}
public static string GetDbEntityValidationMessage(DbEntityValidationException ex)
{
// Retrieve the error messages as a list of strings.
var errorMessages = ex.EntityValidationErrors
.SelectMany(x => x.ValidationErrors)
.Select(x => x.ErrorMessage);
// Join the list to a single string.
var fullErrorMessage = string.Join("; ", errorMessages);
// Combine the original exception message with the new one.
var exceptionMessage = string.Concat(ex.Message, " The validation errors are: ", fullErrorMessage);
return exceptionMessage;
}
public static IEnumerable<Exception> GetInners(Exception ex)
{
for (Exception e = ex; e != null; e = e.InnerException)
yield return e;
}
public static Exception CreateFromDbUpdateException(DbUpdateException dbUpdateException)
{
var inner = GetInners(dbUpdateException).Last();
string message = "";
int i = 1;
foreach (var entry in dbUpdateException.Entries)
{
var entry1 = entry;
var obj = entry1.CurrentValues.ToObject();
var type = obj.GetType();
var propertyNames = entry1.CurrentValues.PropertyNames.Where(x => inner.Message.Contains(x)).ToList();
// check MS SQL datetime2 error
if (inner.Message.Contains("datetime2"))
{
var propertyNames2 = from x in type.GetProperties()
where x.PropertyType == typeof(DateTime) ||
x.PropertyType == typeof(DateTime?)
select x.Name;
propertyNames.AddRange(propertyNames2);
}
message += "Entry " + i++ + " " + type.Name + ": " + string.Join("; ", propertyNames.Select(x =>
string.Format("'{0}' = '{1}'", x, entry1.CurrentValues[x])));
}
return new Exception(message, dbUpdateException);
}
}

This code helped find my problem when I had issue with my Entity VAlidation Erros. It told me the exact problem with my Entity Definition.
Try following code where you need to cover storeDB.SaveChanges(); in following try catch block.
try
{
if (TryUpdateModel(theEvent))
{
storeDB.SaveChanges();
return RedirectToAction("Index");
}
}
catch (System.Data.Entity.Validation.DbEntityValidationException dbEx)
{
Exception raise = dbEx;
foreach (var validationErrors in dbEx.EntityValidationErrors)
{
foreach (var validationError in validationErrors.ValidationErrors)
{
string message = string.Format("{0}:{1}",
validationErrors.Entry.Entity.ToString(),
validationError.ErrorMessage);
// raise a new exception nesting
// the current instance as InnerException
raise = new InvalidOperationException(message, raise);
}
}
throw raise;
}

I was getting this error today and couldn't work it out for a while, but I realised it was after adding some RequireAttributes to my models and that some development seed data was not populating all of the required fields.
So just a note that if you're getting this error whilst updating the database through some sort of init strategy like DropCreateDatabaseIfModelChanges then you have to make sure that your seed data fulfils and satisfies any model data validation attributes.
I know this is slightly different to the problem in the question, but it's a popular question so I thought I'd add a bit more to the answer for others having the same issue as myself.
Hope this helps others :)

I think adding try/catch for every SaveChanges() operation is not a good practice, it's better to centralize this :
Add this class to the main DbContext class :
public override int SaveChanges()
{
try
{
return base.SaveChanges();
}
catch (DbEntityValidationException ex)
{
string errorMessages = string.Join("; ", ex.EntityValidationErrors.SelectMany(x => x.ValidationErrors).Select(x => x.ErrorMessage));
throw new DbEntityValidationException(errorMessages);
}
}
This will overwrite your context's SaveChanges() method and you'll get a comma separated list containing all the entity validation errors.
this also can improved, to log errors in production env, instead of just throwing an error.
hope this is helpful.

Here's an extension to Tony's extension... :-)
For Entity Framework 4.x, if you want to get the name and value of the key field so that you know which entity instance (DB record) has the problem, you can add the following. This provides access to the more powerful ObjectContext class members from your DbContext object.
// Get the key field name & value.
// This assumes your DbContext object is "_context", and that it is a single part key.
var e = ((IObjectContextAdapter)_context).ObjectContext.ObjectStateManager.GetObjectStateEntry(validationErrors.Entry.Entity);
string key = e.EntityKey.EntityKeyValues[0].Key;
string val = e.EntityKey.EntityKeyValues[0].Value;

I dont like exceptions
I registered the OnSaveChanges and have this
var validationErrors = model.GetValidationErrors();
var h = validationErrors.SelectMany(x => x.ValidationErrors
.Select(f => "Entity: "
+(x.Entry.Entity)
+ " : " + f.PropertyName
+ "->" + f.ErrorMessage));

This error also happens when you try to save an entity that has validation errors. A good way to cause this is to forget to check ModelState.IsValid before saving to your DB.

Make sure that if you have nvarchar(50)in DB row you don't trying to insert more than 50characters in it. Stupid mistake but took me 3 hours to figure it out.

Thnaks for your answers, it help me alot.
as i code in Vb.Net, this Bolt code for Vb.Net
Try
Return MyBase.SaveChanges()
Catch dbEx As Validation.DbEntityValidationException
For Each [error] In From validationErrors In dbEx.EntityValidationErrors
From validationError In validationErrors.ValidationErrors
Select New With { .PropertyName = validationError.PropertyName,
.ErrorMessage = validationError.ErrorMessage,
.ClassFullName = validationErrors.Entry.Entity
.GetType().FullName}
Diagnostics.Trace.TraceInformation("Class: {0}, Property: {1}, Error: {2}",
[error].ClassFullName,
[error].PropertyName,
[error].ErrorMessage)
Next
Throw
End Try

it may caused by Property which is not populated by model.. instead it is populated by Controller.. which may cause this error.. solution to this is assign the property before applying ModelState validation.
and this second Assumption is . you may have already have Data in your Database
and trying to update it it but now fetching it.

This might be due to the maximum number of characters allowed for a specific column, like in sql one field might have following Data Type nvarchar(5) but the number of characters entered from the user is more than the specified, hence the error arises.

I have faced same issue a couple of days ago while updating the database. In my case, there was few new non nullable columns added for maintenance which was not supplied in the code which is causing the exception. I figure out those fields and supplied values for them and its resolved.

In my case I have a Table Column name Path which datatype i set was varchar(200).After updating it to nvarchar(max), I have deleted the table from edmx and then again added the table and it wokred properly for me.

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