IDataErrorInfo validation in DataGrid with CellTemplate and CellEditingTemplate

Question

I'm having trouble concerning validation in DataGrid. I'm using IDataErrorInfo validation in model classes.

The problem is in editable DataGrid with separate CellTemplate and CellEditingTemplate (Note is a not-null property - validation returns Error if null or empty):

<!-- some other validated columns -->
<DataGridTemplateColumn Header="Note">
    <DataGridTemplateColumn.CellEditingTemplate>
        <DataTemplate>                                    
            <TextBox Name="textBoxNote" Text="{Binding Note, ValidatesOnDataErrors=True}" />                                    
        </DataTemplate>
    </DataGridTemplateColumn.CellEditingTemplate>
    <DataGridTemplateColumn.CellTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding Note}" />
        </DataTemplate>
    </DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>

On Save button, I check MyObject.Error validation property and if not null I show a MessageBox. The problem is that when changing the first column (not the Note one) to a valid value and then clicking Save button, the .Error property is null - this is expected (although unwanted) behavior because the binding with ValidatesOnDataError on Note property never happened (the TextBox control never even existed!). But if I set the ValidatesOnDataErrors to true on TextBlock then I get the undesired validation on every object shown in a DataGrid (say from a database) that I'm not concerned about; validation can also take a lot of time in this case...

What would be the proper way to handle this issue? I would like to keep validation in model classes (the object should know about whether it's valid or not). Is there any way to force validation of a row-bound object in codebehind (Save button event)? Or should I somehow initialize .Error on object construction? Any other ideas?

EDIT: how could I put the whole row (all cells) into edit mode (CellEditingTemplate)? Then, all of the controls would be loaded and databound, this also means validated...

Thanks to all, DB

Answer 1

Ok, I managed to revalidate the IDataErrorInfo object - kind of forced IDataErrorInfo validation. Otherwise I could add new object to the DataGrid, but properties (except of the edited ones) never got validated.

In the superclass of all of my model objects (that extends IDataErrorInfo) I added this method:

public virtual void Revalidate() // never needed to override though
{
    Type type = this.GetType();

    // "touch" all of the properties of the object - this calls the indexer that checks
    // if property is valid and sets the object's Error property 
    foreach (PropertyInfo propertyInfo in type.GetProperties())
    {                
        var indexerProperty = this[propertyInfo.Name];
    }
}

Now when the user adds new object to DataGrid I manually call myNewObject.Revalidate() method to set the Error property which I check before saving the object to the database. Maybe this is not the best possible solution, but it works for me very painlessly.

Thanks and regards, DB