How to set the value of an Ultracombo to null when it's bound to a string?

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Tom posted over 10 years ago

I've come across a bit of odd behaviour in the ultracombo: When it is bound to field of a nullable type (e.g. a nullable int), and AllowNulls is set to true then when you blank the combo's text via the UI the property the control is bound to is correctly set to null. However, if the combo is bound to a string field then when you clear the text from the combo the underlying property is not updated at all. The combo allows you to move the focus away and is blanked, but the field underneath is still retaining the original value.

Is there a way to change this behaviour?

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Offline Mike Saltzman posted over 10 years ago

Hi Tom,

I tried this out and it's working just fine for me.

I'm attaching my sample here. The grid is there just so you can navigate the current row and see the data. But clear he comb0 and click on another grid row and you can see that the grid cell is blanked out - so the data source is being updated correctly.

WindowsFormsApplication7.zip
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1125

Tom posted over 10 years ago in reply to Mike Saltzman
Hi Mike

Thanks for testing it out and creating the sample - I see what you mean, but actually if you set the value of the cleared cell again via the combo (e.g. to Banana so both the combo and cell say Banana) and then clear the combo again the cell text will then remain as Banana. That's the same symptoms as I had I think, but I haven't used the UltraDataSource before so I'm not completely sure what is going on.

I've attached an example that hopefully illustrates our issue. It consists of a simple class (Class1) with a string property (Class1.SomeText) and a nullable int property (Class1.NullableInt). There are then combos with either a list of strings or a list of ints as their data sources that are bound to those properties. All the binding is using standard .net bindingsources. The combos are set to LimitToList = true and AllowNulls = true.

Steps to reproduce our issue:

Press the top button - message box pops up showing that Class1.SomeText's value is 'Nothing'

pick the value of 'B' in the top combo, press the button, message box pops up showing 'B'

clear the value from the top combo by highlighting the text and pressing backspace

move the cursor to another text box (just to be sure)

press the button again - message box pops up showing Class1.SomeText's value is still 'B' - this is the unexpected behaviour

highlight and delete the 'B' text in the bound textbox

press the button again - message box pops up showing Class1.SomeText's value is now Nothing as expected

(What has also surprised me is that I am now getting the same issues as above when bound to a nullable int which I didn't think we did previously)
NullStringBindingInUltraCombo.zip
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Verified Answer
Offline Mike Saltzman posted over 10 years ago in reply to Tom
Hi Tom,

I tried again using my sample and I am not getting the results you describe. Here's exactly what I did:

Run the sample. Focus is in the UltraCombo and the text "A" is selected.

Press Del - the text disappears.

Press tab - this sets focus to the grid and the grid cell and the combo are both blank.

Click back on the combo and select "Banana"

Press tab - The Combo and the grid cell both show "Banana"

Click back on the combo and clear the text.

Press tab - once again, both the combo and the grid cell are empty.

So then I tried it out with your sample and I am not getting the results you describe there, either. When I get to step 5, both Combos and the TextBox are all blank and when I press the button, I get "Nothing".

So this seems like a problem on your machine. Maybe you need to get the latest service release for NetAdvantage.
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1125

Tom posted over 10 years ago in reply to Mike Saltzman

Hi Mike

Mike Saltzman"]
So this seems like a problem on your machine. Maybe you need to get the latest service release for NetAdvantage.

That was the answer. I upgraded to 13.1 and all was well. Well, it was after I then upgraded everything to .net 4.

As ever, thanks for responding so quickly and helping us get going again.
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