AutoMapper is giving invalid operation exception

Question

On my edit page, I was receiving this error:

Attaching an entity of type failed because another entity of the same type already has the same primary key value.

So, I researched that and came to this.

That lead me to want to use Auto-Mapper, to simplify things.

Here is my code:

if (db.TableName.Find(value.ID).stringProperty.Equals(value.stringProperty, StringComparison.CurrentCultureIgnoreCase))
{
    Table inContextVariable = db.TableName.Find(value.ID);

    Mapper.Initialize(config => config.CreateMap<ModelName, ModelName>());

    Mapper.Map<ModelName, ModelName>(value, inContextVariable);

    db.Entry(inContextVariable).State = EntityState.Modified;
    db.SaveChanges();
    return RedirectToAction("Index");
}

This is leading me to this error:

Additional information: 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.

This table has 1 Foreign Key, and when I debug that Foreign Key has a value of 11, so I am having a hard time understanding this error.

---

UPDATE

---

Imagine if I had a database table that held records containing a person's info such as:

|    ID    |    First Name    |    Last Name    |          Email           |
----------------------------------------------------------------------------
     1           John                Doe             john.doe@test.com
     2           Christopher       Columbus     |  chris.columbus@test.com |

And so on and so on.. now, since a person can only have 1 email address, you have to have safeguards against other users when they are creating/editing records..

For example, if I were to use this application and I wanted to create an account.. I shouldn't be able to successfully fill out the form with an email address that already exists in the database table..I should receive an error message saying something like

That email address already exists! Please enter another email address

Here is that code:

if (db.TableName.Any(x => x.Email.Equals(value.Email, StringComparison.CurrentCultureIgnoreCase)))
{
    ModelState.AddModelError("Email", "This email already exists!");
    return View(value);
}

Now.... what happens when a user successfully creates an account.. then goes to edit their account email address to something that already exists? The same error message should appear, which it does.

BUT when that user created their account, their email address is now in the database table.. so when they go to the Edit page, with their original email, and they hit 'Save', the code will check that email against all email addresses in the database, and it will see that it is already in the database causing the error message to show (please change your email. .etc)..

So I am in need of trying to create an efficient way of checking to see when the user is on the edit page, and hits 'Save' with their original email that it doesn't tell them to change their email.

So for that I have this code:

if (db.TableName.Find(value.ID).Email.Equals(value.Email, StringComparison.CurrentCultureIgnoreCase))
{
    var inContextVariable = db.TableName.Find(value.ID);
    MappingMethods.MapModelName(inContextVariable , value);

    \\ without the mapping.. I receive the error saying 'Attaching an entity of type failed because another entity of the same type already has the same primary key value.'

    db.Entry(inContextVariable).State = EntityState.Modified;
    db.SaveChanges();
    return RedirectToAction("Index");
}

Answer 1

Here is the basic logic I would use here

Table inContextVariable = db.TableName.Find(value.ID);
if(!inContextVariable.Email.Equals(value.Email, StringComparison.CurrentCultureIgnoreCase))
{
    // user input a new email so make sure it doesn't match anyone else
    if(db.TableName.Any(x => x.Email.Equals(value.Email, StringComparison.CurrentCultureIgnoreCase) && x.ID != value.ID))
    {
        // user's new email DOES match someone else's email so handle it
    }
    else
    {
        // no match so do the update

    }

}

No need to handle the outer else because they didn't change their email so you don't do anything!

Note: You will have a race condition here! If two people are both submitting at close to the same time then it is possible for the check to pass but they both end up with the same email. Like let's say they both change to x@y.com but the second person's check is done before the first person's save. But, such is the life for web apps.

Answer 2

With the help of @nurdyguy I came up with this idea. I created another class called MappingMethods which holds this method:

public static void MapModelName(ModelName inContext, ModelName outOfContext)
{
    inContext.ID = outOfContext.ID;
    inContext.stringProperty= outOfContext.stringProperty;
    inContext.OwnerID = outOfContext.OwnerID; \\ foreign key
    inContext.DateCreated = outOfContext.DateCreated;
}

Then in my Edit Action:

if (db.TableName.Find(value.ID).stringProperty.Equals(value.stringProperty, StringComparison.CurrentCultureIgnoreCase))
{
    var inContextVariable = db.TableName.Find(value.ID);
    MappingMethods.MapModelName(inContextVariable , value);

    db.Entry(inContextVariable).State = EntityState.Modified;
    db.SaveChanges();
    return RedirectToAction("Index");
}

This worked.

Answer 3

The whole idea of automapper is to avoid such methods in your static class. Imagine if u had 100 properties? (just for example). Will u copy-paste obj1.prop1 = obj2.prop1?

First of all I would suggest to create a view-model - smth. that will represent a view of your model. Yes, you can create a copy of object with automapper, but it wasn't designed for it.

Try to do smth like this:

1. create a view model - it can be the same as your model or not - it all depends on you (bth it's not a good practice to pass your DB model into views)

2. Map your model to view-model and virce-verce, like this:

   Mapper.CreateMap() .ForMember(d => d.DateCreate, d => d.MapFrom(x => x.DateCreated));