The case of the blank Visual Studio properties window — part 2

Earlier this year I suffered from a case of a Visual Studio properties window that appeared to get “stuck” in the middle of developing an application. It would show up blank and the only way to get it to work was to fix the project and restart Visual Studio (not just close and reopen the solution). For more details, please read the first article.

Blank Properties window in Visual Studio

Although I haven’t written about it, after applying the solution from the first article, my problems weren’t entirely over. Every once in a while, the properties window would get stuck again, and after tweaking the .xsd file a little or reverting it to a previous revision, I could get it to work again. But I never got the feeling that I really understood what I was doing. It would just work sometimes, or not. I even got hesitant to make any changes to the dataset, unless absolutely necessary. But it only happened on that single solution.

Until last week. In an entirely different solution, all of a sudden the properties window was blank again. It’s subtle, you don’t always notice immediately and because of that I could not simply undo the last the thing I did. This solution contained a dataset file too, so after cursing a little (I admit) the first thing I did was revert that and reapply the changes one by one. But this time, that didn’t work. I reverted the dataset to points way before the property editor got broken but still nothing. It was starting to look like the dataset file being the solution was not a generic one, but just the solution for that first project. This time, it was something else. Lees meer over dit bericht

Error when compiling .resx file – Attempt to load a program with an invalid structure

I have seen this before and fixed it, but ran into it again today and could not remember what is was. When compiling a WinForms application in Visual Studio 2010, I got an error message stating “Kan bestand of assembly (…) of een van de afhankelijkheden hiervan niet laden. Poging om een programma te laden met een onjuiste indeling. ” (Roughly translated, “Can not load assembly (…) or one of its dependencies. Attempt to load a program with an invalid structure.”).

When double-clicking the error, it points to a base64-encoded piece of a resx-file, in this case an image stream for an image list.

This is a bug in Visual Studio 2010 that has not yet been fixed. See here on Microsoft Connect.

The workaround suggested by Pellet21 works for me in the mean time. I’ll copy it here to save myself from Googling for it next time:

1.    Open Form in Designer and make needed GUI changes. Close designer and save
2.    Compile project and receive RESX compile error (only forms with Imagelist should have this problem)
3.    Double-click resx compile error to open resx file.
4.    Scroll to top of imagestream.
5.    Edit the top line of the Image stream:
6.    Close and save resx file and recompile.
**NOTE: the only difference are the characters at end “j00LjAuMC4w’ to “j0yLjAuMC4w”

This needs to be done EVERY TIME you open the form in Designer mode.

Initializing a combobox to a blank value might be harder than you think

Combobox troubles again today. No matter how hard I tried to have Comboboxes in my dialog form to initially display blank (SelectedIndex = -1), as soon as the dialog was displayed, the combos would always show the first item in the List that populated it. Despite being set to -1 explicitly. It was driving me nuts.

When created at runtime using a List as DataSource, getting this (empty combos) might be harder than you think

The situation: I had a dialog form that should have a variable number of comboboxes on it, determined at runtime. So the form had an Init method where I dynamically added the comboboxes, and set its DataSource to a List of items (directly, no BindingSource). The form also has a LoadData method, that sets the SelectedIndex of each combo to the actual value from the data, or to -1 of it was unknown or uninitialized at that time. This was to be able to make the combo appear blank instead of preselecting the first item, which was undesired. The caller of the dialog executes Init(), LoadData() and finally ShowDialog().

I was expecting a blank combobox, but it showed the first item in the list preselected. I triple checked that the SelectedIndex was correctly set to -1 at the end of LoadData(), but as soon as the form was displayed, it was 0. What the *** happened there in between and “who” was secretly setting my property!? Lees meer over dit bericht

Jet OleDB 4.0 provider not registered on the local computer

I have a C# WinForms program that attempts to import some data from Excel into a SQL Server database using the Ole DB provider. Today the import suddenly failed with an error message saying that the Jet Ole DB provider was not registered on the local computer.

InvalidOperationException: Jet OleDB 4.0 provider not registered on the local computer

Well, I was pretty sure that it was. So what was wrong then?

Turned out that the Configuration Manager accidentally got reset to “Any CPU” setting. I have an x64 machine on which that leads to running the application in 64-bit mode, in which there is indeed no Jet OleDB provider available (and no Edit-and-Continue either, among other things…).

Setting the target platform to compile to x86 immediately solved the problem.

WinForms ComboBox does not always fire SelectionChangeCommitted

Today I ran into the problem that a ComboBox in my project did not always fire the SelectionChangeCommitted event when I expected it to. To be specific, if a user dropped down the list, used the arrow keys to move to an item, and then TABbed to the next control, the new item would be selected but the event never fired. This was a problem for me, because I relied on this event to filter the items in the next control, depending on the selection made in the first.

Some googling quickly learned that this was a known problem with the ComboBox, although the thread is about the SelectedIndexChanged event, it appears the same error prevents SelectionChangeCommitted from behaving as expected. As user comecme in that thread pointed out, there even was a knowledgebase item including a workaround available from Microsoft. But as he also points out… the workaround does not work.

So I decided to cook up my own solution. This would involve subclassing the Combobox to change the behavior I needed. I had one advantage, I was already using a subclassed ComboBox in all places I needed this behavior, so no Find+Replace was required to replace all standard ComboBoxes with my own.

To this subclassed combobox (named CatalogComboBox) I added the following code:

private CatalogComboItem keepSelection;

protected override void OnEnter(EventArgs e) {
  keepSelection = this.SelectedItem;

protected override void OnLeave(EventArgs e) {
  if (this.SelectedItem != keepSelection)

protected override void OnSelectionChangeCommitted(EventArgs e) {
  keepSelection = this.SelectedItem;

(I used CatalogComboItem because my combo items where typed as such, but you can always use object.) It’s a not spectacularly elegant or high-tech solution, but it works like a charm.

The case of the Visual Studio blank properties window

I experienced the strangest thing with my installation of Visual Studio 2008 last Friday. In the middle of developing a Windows Forms application, I noticed that the Properties window had stopped working. It was still there, just blank, and so was the dropdown above it where the components usually reside.

Update 19-12: This blog post will be revised soon. I have since experienced this same error under different conditions which had a different solution.

Update 20-12: This blog post is superseeded by this one. I have now found a generic strategy to follow if this situations occurs. The solution presented below was probably a one-time fix that will most probably not help you. Please read the new article.

Blank Properties window in Visual Studio

This was not just with the current file, but for all files in my solution. It would not even display the mainly informal properties of the current file selected in the Solution Explorer. Closing the solution and re-opening it did not help. Hiding the properties window and re-showing it did not help. Google led me to several suggestions, most of them telling me to execute a command in the Visual Studio command prompt (devenv /setup) would fix things. Nope, not for me. Starting VS in safe mode to eliminate plugins. Still blank. Even other solutions I opened now had a blank properties window. Oh dear. I was now getting worried that I broke something very serious in my VS installation.

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