what a feisty little interface. I had about 10 edit controls, 6 of them with similar behavior, they should all be validated and it should be possible to do a database lookup based on the edit fields content. I figured a 'search icon' next to each edit field would be the best UI design here. Fine I placed a picturebox on 6 of the edit controls' right side, looked ok, but what troubled me was the decoupling between the edit controls and the lookup icon + each time I changed my design it got messy moving all them edit controls and pictureboxes around..if only each edit control was bundled with the picturebox and all the validation and searching functionality was associated with the edit control. My thoughts actually went back to the good old Win32/16 days ... remember the SetProp function! where you could associate custom data with each Control. After a quick walk down memory lane, I stumbled over the IExtenderProvider interface while trying to squeeze ErrorProvider onto my form also.
You must implement only 1 method, the CanExtend method where cast your vote on what type of control you want to extend.
[ProvideProperty(Search, typeof(string))]
public class SearchProvider : Component, IExtenderProvier
{
......
.......
private Hashtable hash = new Hashtable();
//Forms designer will pass in every control to see if we will extend the control
public bool CanExtend(object ctrl)
{
//make sure my edit control is on my form.
if(ctrl.GetType()== typeof(TextBox))
{
if((((Control)ctrl).FindForm()==null)
return false;
else
return true;
}else {
return false;
}
}
public void SetSearchProp(Control ctrl, string sValidate)
{
if(!DesignMode)
{
//create a class that handles the validation with Regex
JCSharp.Utility.ValidateSearch vs = new JCSharp.Utility.ValidateSearch(ctrl, sValidate);
//register the validating event
ctrl.Validating += new CancelEventHandler(vs.OnValidating);
//create my search box
JCSharp.utility.SearchHelper sh = new JCSharp.utility.SearchHelper(ctrl);
.....
}
hash[ctrl]=sValidate;
}
public string GetSearchProp(Control ctrl)
{
return (string)hash[ctrl];
}
........
}
we need to provide accessor method which we indicate with the ProvideProperty
....
....
public class SearchHelper
{
public SearchHelper(Control ctrl)
{
PictureBox pic = new PictureBox();
pic.Image = GetImage();
pic.Size = new Size(16,16);
pic.Location = new Point(ctrl.Right + 10, ctrl.Top);//looks okay to me.
ctrl.Parent.Control.Add(pic);
//when we click on the picturebox, do a database loopup based on the content of the edit control
pic.Click += new EventHandler(OnLookup);
}
.......
}
now call the searchProvider like this on your form
searchProvider1.SetSearchProp(TextBox1,".*@.*"); //validate email.
searchProvider1.SetSearchProp(TextBox1,"");
The IExtenderProvider interface, a very sparse interface, very easy to ignore :) but solves all your problems when you want to extend a control with extra properties.
"Have you seen any code reuse lately ?"
-- Anonymous attendee, OOPSLA 2004 :)
8:50:19 PM 
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