"Define a Csla Property" VB snippet

Lnk posted on Wednesday, August 30, 2006

Hi all...

We have an exception ocurred in our project due to the use of "Define a Csla Property" snippet:

    Set(ByVal value As $PropertyType$)
        CanWriteProperty(True)
        If Not $PrivateVariable$.Equals(value) Then
          $PrivateVariable$ = value
          PropertyHasChanged()
        End If
    End Set

When editing a string property in a grid. If you delete the cell content the $PrivateVariable$ value will be Nothing. The equals function causes an exception when setting a correct value because $PrivateVariable$ is Nothing.

We propose to change the line, as in Project Tracker, for using the <> operator.

The only side effect is that all our property types must implement the <> operator. But this can be noticed when coding. The we could choose to use Equals with Nothing check or implement the <> operator.

What do you think about?

Thanks.

Emilio.

Tim FOrd replied on Wednesday, August 30, 2006

I think I understand what you are trying to say, I had an issue with this before.

I found that the declaration was causing the issue, if you have a string value you will need to set it to string.empty in the declaration.

Dim _Value as String = String.Empty and then you can evaluate the value when setting the property.

If you don't i believe it throws and error because the variable hasn't been initiated.

Tim.

Lnk replied on Thursday, August 31, 2006

Tim, is not a question of variable inizialization.

The thing is that the Datagridview is sending Nothing to my property when I delete the cell contents (in this case the property is a string). Then when I write a correct value on the cell the equals fuction fails becasuse the member variable is nothing.

Thanks anyway...

Emilio.