Getting exact error type in from DbValidationExcep

问题:

I have the situation where I'm initializing my model in DatabaseInitializer() for EF 4.1 and get this annoying error "Validation failed for one or more entities. See 'EntityValidationErrors' property for more details." So, I go to this EntityValidationErrors and there is a field {System.Data.Entity.Validation.DbEntityValidationResult} which gives me no information at all about what field it was unable to initialize. Is there a way to get more info about this error?

To clear things out:

I know how to fix the string length problem. What I'm asking is how do I get the exact field name that is breaking the model.

回答1:

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

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.

For Visual 2012+ users who care only about the first error and might not have a catch block, you can even do:

((System.Data.Entity.Validation.DbEntityValidationException)$exception).EntityValidationErrors.First().ValidationErrors.First().ErrorMessage

回答2:

You could try this in a try/catch block?

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);
        }
    }
}

回答3:

The best solution in my opinion, is to handle this kind of errors in a centralized way.

just add this method 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.PropertyName + ": " + 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.

hope this is helpful.

回答4:

Well, I had same problem. My model worked good in EF CTP5 but failed to build in 4.1 with the same error ""Validation failed for one or more entities" when I tried to initalize it. I figured out that I had property:

public string Comment {get; set;}

Then in seed method in overrided initializer, I had quite a bit long (about 600 letters) comment.

I think the point is: in EF 4.1 you have to set data annotations explicitly in some cases. For me, setting:

[StringLength(4000)] 
public string Comment {get; set;}

helped. It's weird since CTP5 had no problems with that.

回答5:

I found it useful to create a SaveChanges wrapper which makes the EntityValidationErrors more readable:

Public Sub SaveChanges(entities As Entities)

    Try
        entities.SaveChanges()

    Catch ex As DbEntityValidationException

        Dim msg As New StringBuilder
        msg.AppendLine(ex.Message)

        For Each vr As DbEntityValidationResult In ex.EntityValidationErrors
            For Each ve As DbValidationError In vr.ValidationErrors
                msg.AppendLine(String.Format("{0}: {1}", ve.PropertyName, ve.ErrorMessage))
            Next
        Next

        Throw New DbEntityValidationException(msg.ToString, ex.EntityValidationErrors, ex)

    End Try

End Sub

and then changed 'entities.SaveChanges()' to 'SaveChanges(entities)' in my entire project