I am using delphi xe2 (fully updated) and Express QuantumGridSuite 13.2.2 . I've much columns on grid and i set RepositoryItem for some columns. EditREpository component is on another form. Some times that columns repositoryItem property is clearing randomly. I think that something is triggering that but i couldn't found what is this about and how is that do? Tnks for your helps.
This problem of component values becoming "lost" at design time is a known phenomenon, even with EMBA's own components. Usually, it manifests itself when forms are first opened in the IDE.
In my experience, ymmv, it nearly always happens with a property of some component of form A which references a component on form B, and it seems to happen more frequently if form A is opened in the IDE before form B.
Anyway, there are things you can do to try and identify the problem and at least one work-around you can use until you do. But, before you start, the very first thing to do, if you haven't already, is to ask Devex whether they know about the problem. No disrespect to the readership here but they are more likely to know, and it may turn out that you've missed a maintenance update that fixed it.
When I've had it happen with components I've written myself, usually it has been caused by some error in my coding of the component's initialization and/or property setters. In my own components' cases, I've always been lucky in that although at first the behaviour seems random, in fact there has turned to be a specific sequence of actions in the IDE that triggers it. If you can identify a reproducible sequence of actions, you're 90% of the way to getting the problem fixed.
The best place to start is to make a reference back-up of your code in its pre-problem state. Then try out various sequences of actions in the IDE, rolling back to your reference in between, until you find one that provokes the problem. If this sounds tedious, it is, but you may get lucky and spot a pattern early on. If you don't, then keep reminding yourself that the problem only seems random because you haven't spotted the pattern yet.
However, I have the impression (though no proof) that another misbehaving component can disturb the setting of the properties of the component which is losing the value. So, one thing to look at is what other components are on the same form as your affected one. Not all have the same pedigree as the Quantum Grid and its siblings from Devex.
Things I've found effective to isolate the problem with components I've written myself are:
As you may have noticed, one of the most troublesome things about this problem is that if the component is on a rarely-used form, often the first you hear of it is when a user reports it.
Anyway, with all that said, if you can come up with a reproducible test case involving only Devex components and the standard ones, that can be submitted to them for investigation, I'm sure it won't take them long to find and fix the problem. And I'm sure they will fix it if it's in their own code (I wish the same were true of EMBA themselves).
However, without a reproducible test case, I think the best you can hope to do is to add explicit code to your form's creation to set the component value at run-time, e.g. when the form is first created. With my own problem components, once or twice I've found that careful tracing into the code I've added to do this has led me to the cause of the problem.