problem with dropdownlist selected item

[Aaron Prohaska]

I'm having the problem with this drop down list on postback. For some
reason both the ListItems get selected when I change the selected item.
Using the code below I'm building the drop down list in the overriden
CreateChildControls method and setting the selected item. Then when I
change the item in the drop down list the list is rebuilt from
viewstate, but the initial item is still selected causing the error
below.

I also have a number of other drop down lists in this custom control
that work just fine, so its a bit confusing to me why only this one
doesn't work.

Can anyone see what might be causing this?

ERROR:

System.Web.HttpException: A DropDownList cannot have multiple items
selected.

CODE:

CreateChildControls()
{
this.rearTravelList =
(DropDownList)Page.FindControl("rearTravelList");

this.rearTravelList.AutoPostBack = true;
this.rearTravelList.SelectedIndexChanged += new EventHandler(
this.SelectedRearTravelChanged );
if ( !Page.IsPostBack )
this.BuildRearTravelList();
}

private void BuildRearTravelList()
{
ListItem xCountryItem = new ListItem();
ListItem freeRideItem = new ListItem();

xCountryItem.Text = "X Country 2.25-4.49in";
xCountryItem.Value = RidingStyle.XC.ToString();

freeRideItem.Text = "Free Ride 4.5-6in";
freeRideItem.Value = RidingStyle.FR.ToString();

this.rearTravelList.Items.Add( xCountryItem );
this.rearTravelList.Items.Add( freeRideItem );

this.SetSelectedItem( this.rearTravelList,
this.RidingStyle.ToString()
);
}

private void SetSelectedItem(ListControl list, string textValue)
{
list.ClearSelection();
ListItem item = list.Items.FindByValue( textValue );
if ( item != null )
item.Selected = true;
}

 

[Aaron Prohaska]

I have an update to this problem. In the CreateChildControls method I
add the line

this.rearTravelList.ClearSelection();

so the code looks like this.

CreateChildControls()
{
this.rearTravelList =
(DropDownList)Page.FindControl("rearTravelList");

this.rearTravelList.ClearSelection();
this.rearTravelList.AutoPostBack = true;
this.rearTravelList.SelectedIndexChanged += new EventHandler(
this.SelectedRearTravelChanged );
if ( !Page.IsPostBack )
this.BuildRearTravelList();
}

After adding the new line of code I can now select the new item and it
works correctly in selecting the item in the dropdownlist and doesn't
give me the multiple items selected error, but in the process of doing
this the SelectedIndexChanged event is not being fired.

Can anyone explain this?

Aaron

 

[NoOne]

You have to note when CreateChildControls is called in the page lifecycle
and be careful what you do there, especially if your control is put onto a
web form as opposed to added in the codebehind logic. If its called early in
the page construction then IsPostBack might not be set yet, which would
explain why you were getting duplicated items. Also this would also explain
why your selected changed event is not getting fired.

 

[Aaron Prohaska]

Ok, I understand that, but I don't know what to do about it. Would you
please take a look at another post that I just made to this group with
the subject "Composite control building architecture problem". It has a
much more complete example of my problem with all the code that goes
along with it.

thanks for the reply,

Aaron