On a recent project, one of my developers was trying to extend the combobox in a winforms project.  We wanted to reuse the same combobox in several places. 

The combobox would always have the same objects bound to it, and we wanted a few functions extra functions on the combobox that would centralize some functionality.

So we inherited from combobox, and in the constructor of our class we created the 5 objects that we need in the dropdown and we added them to the combobox items collection.

So far so good.

But we found that when we made a change in the designer for a form that uses this combobox, the designer put stuff in the designer.vb file.  Lines that were trying to add items to our combobox.

It used the .items.AddRange(…) function and tried to add 1 item for every item that we add in the contructor.

Basically it was looking like the designer instantiated the control, and then was trying to serialize the items in the combobox when we would change anything on the form.

This would eventually cause the designer to blow up, as well as a similar error when we tried to run the compiled code.

The solution was elusive and quite a pain.

Some credit needs to go to Andre for his post.

Basically we needed a way to tell in our code if the control was being hosted in the VS designer.  If it was, then we skipped the part where we populated this dropdown.

So first thing we did was create 2 functions to figure out where the control is hosted:

Private Function IsDesignerHosted() As Boolean
    Return Me.IsControlDesignerHosted(Me)
End Function
Private Function IsControlDesignerHosted(ByVal ctrl As Control) As Boolean
    If ctrl IsNot Nothing Then
        If ctrl.Site IsNot Nothing Then
            If ctrl.Site.DesignMode Then
                Return True
            Else
                Return IsControlDesignerHosted(ctrl.Parent)
            End If
        Else
            Return IsControlDesignerHosted(ctrl.Parent)
        End If
    Else
        Return False
    End If
End Function

Then, because it turns out that testing the DesignMode is useless when you are doing the testing from the constructor, so I had to move the databinding into it’s own function along with a instance variable to make sure we only do this one time.

Private cbInit As Boolean = False
Private Sub MyControl_VisibleChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.VisibleChanged
    If Not cbInit Then
        cbInit = True
        If Not Me.IsDesignerHosted Then
            '*** add items here
        End If
    End If
End Sub

There it is!

I have been accepting resumes for a while now trying to find developers for a client of mine.

I will be updating this article from time to time with new stuff.

DO have someone proofread your resume, cover letter, and email body.  Espically if you are not a native english speaker.  If you want your resume to go directly into the trash, then please, write your email with lots of grammer and spelling problems.

DON’T write in your cover letter that, while you don’t have the skills/experience they are looking for, you DO have the skills/experience that really matters.  You have just managed to tell the person reading your resume that a) you don’t have the skills they need, b) you think you are smarter than the person who came up with the needed skills/experience, and c) you are probably not easy to get along with.  All in the first sentence of your cover letter: BRAVO!

DON’T send a 9 page resume including every project you have ever worked on and details about said project.  I remember when I was told that resumes should be 1 page long (2 at the most) and I thought how wrong that was.  “My resme will be so awesome, 2 pages can’t contain it!”  I realized very quickly how wrong I was.  I don’t need to know the specifics of some project you worked on for 3 months back in 2002, and I don’t need to know a list of every programming langauge, technique, or technology that you have ever touched. 

DO supply a cover letter, or at least turn your email into your cover letter.  It will get you bonus points.

DON’T include a stupid signature on your emails.  I actually received a resume that was signed like this:

—
If fishes could talk they’d ask for legs

Ok I guess that is somewhat funny in a Jack Handy kinda way, but it really doesn’t belong on an job application email.

DON’T list “Internet Connection Technologies” that you have experience with.  I swear I got a resume with this as the 2nd heading (after education).  It listed “AOL Dial Up, AOL High Speed DSL, SBC DSL”.  Before you start thinking, ok well maybe these were projects they worked on, you know, like working on the team to create AOL’s dial up service… no this was not what they meant, it was clear from the rest of the resume.

DON’T just make up stuff if you don’t know the answer to a question.  This isn’t the ACT: there are penalities for guessing (it makes you look really stupid).  Now clearly there is a difference between making an educated guess (or talking in generalities instead of specifics) and trying to totally pull something out of thin air.  I recently interviewed a candidate who said he didn’t have any project experience using AJAX but was aware of AJAX technologies.  So I asked him, can you explain how AJAX works?  I wasn’t expecting much, just something about using client side script to make calls to the server w/o reloading the entire page.  Instead the answer we got back was “It’s like JAVA running on top of Microsoft.”  Up until that point I hadn’t decided if this guy was qualified, and had he simply said “No, I am sorry I am not that familiar with AJAX” I probably would have still been considering him, but his terrible attempt at an answer removed all doubt that he was not qualified.

You were a good developer and created an enum to represent the integer values that are being passed into your method.

It makes life easy for everyone.  Good job.

But now you realize that ANY integer can be passed into your function, even though your type only defines a handful of values.

Well, you need to validate the enum values that are coming into your method.

This can be done quickly with the following code snippet:

If Not [Enum].IsDefined(localId.GetType, localId) Then
    Throw New System.ComponentModel.InvalidEnumArgumentException("Invalid local value.")
End If

In this example localId is the variable name of type LocalType.