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Breeze SaveChanges issue with Ie10

2014/09/25

Every new technology is an hard path , an high mountain to climb.

I’m working to an MVC project with ASP.NET 4.5 , Breeze and Angular, authentication done with the new ASP.NET Identity, Entity Framework 6.

The big problem , for the average developer (me) , is:

  • For Microsoft, on MSDN you can find a lot of verbose pages about the syntax: an simple CRUD example using these technologies , add update delete of records, is hard to find.
  • For thirdy parties technologies you can find abstruse , overcomplexed samples ; but still there is a lack of a simple table management with CRUD operations.

In every case the samples simply ignore (at the least the ones that i discover with Google) the everyday questions with concurrency : another user could have deleted the record that you are trying to save, or you are trying to save a record of a table where there is an unique index for a field.

Ok , this was the rant, now the problem.

The code is about the update of a record in a Vehicle Classes table (ClassiMezzi).

Using Breeze, in a BreezeController (a class decorated with “[BreezeController]”) the typical sample for an update is

[HttpPost]
public SaveResult SaveChanges(JObject saveBundle)
{
    return _repo.SaveChanges(saveBundle);
}

This works with Ie11, the latest Firefox, Chrome, Safari; _repo is an repository object that at the end calls the Entity Framework context provider (in our sample EFContextProvider<ClassiMezziContext>)

But if you try to use this method for adding a new record on a table where there is an index UNIQUE, there are troubles with the error messages using Internet Explorer 10.

For these new apps i simply don’t consider Ie < 10; if you are still using Ie6 , Ie7.. time to upgrade …but to ignore the previous version is a bit excessive, for me: i test everything with the latest Firefox, Chrome also under Linux Android and Mac, for Ie to test the latest version and the previous seems reasonable.

And so, testing the code with multiuser issues (record deleted from another user, check constraints, UNIQUE indexes) i discovered the problem.

From the javascript side , the controller is called with an Ajax call with callbacks for success or failure:

function saveFailed(error) {
    try {
        manager.detachEntity(service.ClasseMezzoEntity);
    }
    catch (ex) { }
    service.ClasseMezzoEntity = null;
    if (error.httpResponse.status === 401 || error.httpResponse.status === 403) {
        logError(localize.localizeText("UnauthorizedOperation"), null, true);
        return;
    }
    //var strMsg = breeze.saveErrorMessageService.getErrorMessage(error).toLowerCase(); old version ok with Ie11 , not Ie10
    var strMsg = error.httpResponse.data.Errors[0].toLowerCase();
    if (strMsg.indexOf("entities may have been modified or deleted since entities were loaded") > 0) {
        logWarning(localize.localizeText("AnotherUsrHasChangeData"), null, true);
        return;
    }
    if (strMsg.indexOf("ix_classimezzi") > 0) {
        logWarning(localize.localizeText("ClassNameDuplicated"), null, true);
        return;
    }
    if (strMsg.indexOf("errdelete:anotheruser") > 0) {
        logWarning(localize.localizeText("AnotherUsrHasDeleteData"), null, true);
        return;
    }
    //  other code for unknown error management
    var msg = breeze.saveErrorMessageService.getErrorMessage(error);
    // etc.
};
 
function saveClasseMezzo() {
    service.isSaving = true;// see at the end of this module
    service.lastSaveSuccess = true;
    return manager.saveChanges()
        .catch(saveFailed)
        .then(saveClasseMezzoAttemptDone);
};

For example we try to add another ClasseMezzo (Vehicle class) with the same name of an existing item on the the db table.

With Ie11 and other latest browsers the first controller code is ok , and if our ajax call fails because the UNIQUE index the first

var strMsg = breeze…. commented code works perfectly.

But while with Ie11 etc. the error.message in javascript contains the string “Cannot insert duplicate key row …” with the index name that helps to manage the error (in this sample the index name is “ix_classimezzi”) in Ie10 we get


That is an anonymous “An error has occurred” that can’t help to manage the error, and no trace of the original SQL error in httpResponse: a big trouble if i would to say to the customer “you are trying to insert an duplicate item” because could be another thing , for example an SQL check violation.

The problem is the simple approach in the WebApi2 controller.

In order to manage correctly the errors coming from multiuser issues the WebAPI2 controller code must be:

[HttpPost]
[Authorize(Roles = "PowerUser")]
public SaveResult SaveChanges(JObject saveBundle)
{
    SaveResult objRes = null;
    List<object> objErr = null;
    var classimezziList = JsonConvert.DeserializeObject<List<ClassiMezzi>>(saveBundle.SelectToken("entities").ToString());
    try
    {
        objRes = _repo.SaveChanges(saveBundle);
        return objRes;
    }
    catch (Exception ex)
    {
        var keyMappings = new List<KeyMapping>();
        objErr = new List<object> { JsonConvert.SerializeObject(ex.Message) };
        return new SaveResult()
        {
            Entities = classimezziList.Cast<object>().ToList(),
            Errors = objErr,
            KeyMappings = keyMappings
        };
    }
}

Let’s examine the code.

We pass to the controller an JSON object , that we want deserialized in order to correctly manage the error; note in the catch management code: is explicitly created an SaveResult object , instead of the automatic creation.

Setting the Errors field to something != null , in our case the error message serialization, we cause the call of the javascript failure callback , and in the javascript failure code the message must be read as

var strMsg = error.httpResponse.data.Errors[0].toLowerCase();

because when the code is falling back we have this , now:


So we can manage the things as in the next rows.

This is valid also for Ie11 , and Firefox, Chrome under Windows, Linux, Mac, Android.

At least, this is the situation with the current latest Breeze (1.3.8)

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