I've browsed through loads of posts on more or less my type of problem, but I'm unable to find the exact solution to my problem.

I based my datatype on the http://www.nibble.be/?p=24 example. It's a listbox with static list items, which triggers some other controls in it's selectedindexchanged event. That's also where I set the umbracoValue to selected listeitem. 

I've registered  the datatype as database datatype nvarchar, and I run my datatype without problems, but the value I hope to assign is not saved to the database/xml data.

When I run my usercontrol from VS2010 the umbraco value is both got and set.
My code (the interesting part of it):

 
 
public string umbracoValue;
 
 
public object value
{
 
 
get
{
 
 
return umbracoValue;
}
 
 
set
{
umbracoValue = 
 
value.ToString();
}
}
 
 
protected void Page_Load(object sender, EventArgs e)
{
 
 
if (!Page.IsPostBack)
{
 
 
if (umbracoValue != null)
{
 
 
if (umbracoValue.ToString() != "")
{
lbTemplates.SelectedValue = umbracoValue.ToString();
mvTemplates.ActiveViewIndex = lbTemplates.SelectedIndex;
lblTemplateDescription.Text = getDescription(lbTemplates.SelectedIndex);
}
 
 
else
{
umbracoValue = 
 
"template1";
lbTemplates.SelectedIndex = 0;
mvTemplates.ActiveViewIndex = 0;
lblTemplateDescription.Text = getDescription(0);
}
}
 
 
else
{
umbracoValue = 
 
"template1";
lbTemplates.SelectedIndex = 0;
mvTemplates.ActiveViewIndex = 0;
lblTemplateDescription.Text = getDescription(0);
}
}
}
 
 
protected void lbTemplates_SelectedIndexChanged(object sender, EventArgs e)
{
mvTemplates.ActiveViewIndex = lbTemplates.SelectedIndex;
lblTemplateDescription.Text = getDescription(lbTemplates.SelectedIndex);
umbracoValue = lbTemplates.SelectedValue;
}