CODEWITHSUNDEEP
entity-frameworkmappingt4
Ucodia
Ucodia

Reputation: 7710

Implementing a custom non-mapped property on entities

I am currently developping an application which object model and persistence layer is built using the Entity Framework model designer.

One of the requirements I have is to provide a status to my entities that could let me know whenever they are in a "dirty" state (modified), when the status change occurs and, most important, working in a disconnected mode. So I started modifying the T4 template to add a IsDirty boolean property upon generation of those entities, added an event that is fired whenever IsDirty changes and added this.IsDirty = true in the xxxChanged methods of all scalar properties.

Everything works great when the entity is not attached to its context but when attached, whenever a property is changed, thus changing the IsDirty value to false, I receive this exception:

The property 'IsDirty' does not have a valid entity mapping on the entity object. For more information, see the Entity Framework documentation.

So what am I doing wrong here? I don't want this property to be mapped in my database as it is just an object status that only matters when the object is "alive". Is there an attribute I should use to decorate the IsDirty property? Or should I derive EntityObject and implement the status mechanism? Or maybe you have any better advice on how to implement this?

Thanks.

Edit: I am using Entity Framework 4.0 with EDM designer.

Here is the piece of code generated into every base entity:

private bool isDirty;   
public event EventHandler DirtyStatusChanged;

public bool IsDirty
{
    get
    {
        return this.isDirty;
    }

    internal set
    {
        if (this.isDirty != value)
        {
            ReportPropertyChanging("IsDirty");
            this.isDirty = value;
            ReportPropertyChanged("IsDirty");
            ReportDirtyStatusChanged();
        }
    }
}

protected void ReportDirtyStatusChanged()
{
    var handler = this.DirtyStatusChanged;

    if(handler != null)
    {
        handler(this, EventArgs.Empty);
    }
}

Upvotes: 1

Views: 692

Answers (1)

Ucodia
Ucodia

Reputation: 7710

I finally found the error myself. The problem lied inside my property setter. Instead of calling ReportPropertyChanged/ing I should have called OnPropertyChanged/ing.

ReportPropertyChanged/ing implies for the context to search for changes between the original and the current entity value but as this property is just a status object that has no mapping to a store, the concept of original value makes no sense, thus making the context failing to find a correct mapping for this property.

Using OnPropertyChanged/ing just fixed it.

Upvotes: 1

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