Sharepoint 2007 Webpart variables problem on reload - sharepoint

Question

I'm having trouble with the webparts variables... I came from standard ASP language, so, to me, store variables in session and other parts is the common way to do everything =)
Now i had to create a webpart, the wp has to write a graph from parameter and i cannot understand HOW variables works: i cannot understand WHEN saved and WHEN erased and other thing like this!
Let me explain: i have a web part with the configuration toolbar on the right in which i put the values.. Everytime a button is pressed or a value in the dropdown list changes, it raises an event which causes the "CreateChild" function..
Many times the data is "stored", other time they are not!
That's the way i used to store value (in the ApplyChanges override function):
WPChartGenerator wpParent = (WPChartGenerator)this.ParentToolPane.SelectedWebPart;
wpParent.WebUrl = txtWebUrl.Text.Trim();
And in the CreateChild event i get the value like:
WPChartGenerator wpParent = (WPChartGenerator)this.ParentToolPane.SelectedWebPart;
this.ddlWeb = new DropDownList();
this.ddlWeb.ID = "ddlweb" + wpParent.ID;
ddlWeb.SelectedValue = wpParent.WebService;
Now.. Sometimes this works, for example, when i push a button I invoke in the code of the button and then the code to store every value.. In some case (like buttons) this works, in other (like dropdown list index changed event) this fails and i found every object in the wpParent equal to it's initial value.
Another thing i noticed, is that in certain cases when an event is triggered, the first thing to be executed (even first than the event's associated code) il CreateChild (even first than OnLoad!!!)
Can anybody tell me what I'm doing in the wrong way? Do anybody has a good tutoria for this matter?
Thanks & sorry 4 my School level English =)
Forget to say that every variable has been implemented as a Property, like that:
[WebBrowsable(false)]
[Personalizable(PersonalizationScope.Shared)]
[WebPartStorage(Storage.Shared)]
public string WebUrl
{
get
{
return this.webUrl;
}
set
{
this.webUrl = value;
}
}

Answer 1

I can't see all the code there so I don't really know what you're doing wrong (i.e. do you actually have an ApplyChanges method) but from the way you've worded your question it sounds like you really need to start at the beginning, follow one of these walkthrough tutorials and make sure you understand the basics and then start adding in the code for your project.
MSDN - Creating Web Parts for SharePoint (VS2010)
MSDN - Walkthrough: Creating a Basic SharePoint Web Part (WSS 3.0)
Developing SharePoint 2007 Web Parts