ASP.NET

Re: Dropdownlist not responding to the "OnSelectedIndexChanged" method.

22-Jul-09 9:48

I have several dropdownlists on my page. The first works as expected and populated the the datasets for the other two and displays them on the screen.

My issue arises once I make a selection from the 2nd and 3rd dropdownlists. It appears that the onSelectedIndexChanged method is not firing.....

<asp:Label ID="Label3" runat="server" Text="Study Selection"></asp:Label>&nbsp;&nbsp;
<asp:DropDownList ID="DropDownList3" runat="server" AutoPostBack="True" onSelectedIndexChanged="displayDefinitions" >
</asp:DropDownList>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<asp:Label
    ID="Label1" runat="server" Text="Row Selection" Visible="False"></asp:Label>&nbsp;&nbsp;
<asp:DropDownList ID="DropDownList1" runat="server" Visible="false" onSelectedIndexChanged="nextStep"  >
</asp:DropDownList>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<asp:Label
    ID="Label2" runat="server" Text="Column Selection" Visible="False"></asp:Label>&nbsp;&nbsp;
<asp:DropDownList ID="DropDownList2" runat="server" Visible="false" onSelectedIndexChanged="nextStep" >
</asp:DropDownList>

DropDownList3 works fine.
DropDownList1 and DropDownList2 do not. I can make a selection, but the underlying code is not called.

I'm sure it's going to be something deceptively simple, but I'm just not seeing it.
Thanks for any help offered.

Blue_Boy22-Jul-09 9:54

Blue_Boy

22-Jul-09 9:54

Did you set AutoPostBack="True" to DropDownList1 and DropDownList2 ?

Why you don't rename controls with better meaningful names?!

I Love T-SQL
"Don't torture yourself,let the life to do it for you."
If my post helps you kindly save my time by voting my post.

Re: Dropdownlist not responding to the "OnSelectedIndexChanged" method.

Brij22-Jul-09 9:55

Re: Dropdownlist not responding to the "OnSelectedIndexChanged" method.

22-Jul-09 9:55

Set AutoPostBack true for DropDownList1 and DropDownList2 as you did in DropDownList3 as below

<asp:DropDownList ID="DropDownList1" runat="server" Visible="false" AutoPostBack="True" onSelectedIndexChanged="nextStep"  ></asp:DropDownList>

<asp:DropDownList ID="DropDownList2" runat="server" Visible="false" AutoPostBack="True" onSelectedIndexChanged="nextStep"  ></asp:DropDownList>

Cheers!!
Brij

TMFoust22-Jul-09 10:06

Re: Dropdownlist not responding to the "OnSelectedIndexChanged" method.

22-Jul-09 10:06

Nope, that's not it. If I set AutoPostBack, the dropdownlist does not retain the selected change.

(As a side note, this is proof of concept page, so will not be retained, otherwise, yes, I'd have more meaningful element names.)

Christian Graus answererd a similar question (Re: Problem in handling SelectedIndexChanged event of a dynamically created drop down) and stated that the dropdownlist needed to be created before page load. I tried that and got an error that the variable I need to populate the next dropdownlist is not valid.

I'm close. I know it.

Abhijit Jana22-Jul-09 10:13

Re: Dropdownlist not responding to the "OnSelectedIndexChanged" method.

22-Jul-09 10:13

TMFoust wrote:
Nope, that's not it. If I set AutoPostBack, the dropdownlist does not retain the selected change.

That because you did not check the Page.ISPostBack Property. Where you bind the data in Dropdown list?

Try this in Page_Load()

if(!Page.ISPostBack)     // This will load the data if the page is not a post back request.
   {
    //Bind Data in Dropdown list
   }

TMFoust wrote:
Christian Graus answererd a similar question (Re: Problem in handling SelectedIndexChanged event of a dynamically created drop down) and stated that the dropdownlist needed to be created before page load.

He tolds about the dynamic Control. Cause All the view state and Postback data loads just before the Page_Load(). So if your creates any control after Page_Load(), it will not able to load Pastback and View State Data. So that it is recomanded to Create Dynamic control in Page_PreInit() Event.

Hope this will clear your doubts. Smile | :)

cheers,
Abhijit
CodeProject MVP
Web Site:abhijitjana.net
When you ask a question, remember to click "Good Answer", If the Answer is helps you.

Brij22-Jul-09 10:13

Re: Dropdownlist not responding to the "OnSelectedIndexChanged" method.

22-Jul-09 10:13

Do you create Dropdownlist dynamically?

If yes,then you need to to create it before pageload mainly in Page_Init or PreInit, for getting all the properties of Dropdownlist like viewstate etc.

Debug your application you must be resetting it somewhere after postback Smile | :)

Cheers!!
Brij

TMFoust22-Jul-09 10:30

Re: Dropdownlist not responding to the "OnSelectedIndexChanged" method.

22-Jul-09 10:30

Abijit, thanks, but when I add the (!page.ispostback) the dropdownlists no longer get dynamically created.

Brij, I can't initialize DropDownList1 and DropDownList2 in Page_init because they depend on a selection from DropDownList3 to populate the datasets? I get variable not valid errors when I try.

Like I said, I feel wretchedly dumb, but this is frustrating me.

Abhijit Jana22-Jul-09 10:38

Re: Dropdownlist not responding to the "OnSelectedIndexChanged" method.

22-Jul-09 10:38

Just Tell me what is your exact requirments? Smile | :)

cheers,
Abhijit
CodeProject MVP
Web Site:abhijitjana.net
When you ask a question, remember to click "Good Answer", If the Answer is helps you.

TMFoust22-Jul-09 10:47

Re: Dropdownlist not responding to the "OnSelectedIndexChanged" method.

22-Jul-09 10:47

Dropdownlist3 has a list of studies (databases).
The user selects which one to use and then gets 2 lists (Dropdownlist1 and dropdownlist2) containing lists of definition files.
The user has to select a row file and a column file to populate a webgrid for statistical analysis. These selections are supposed to enable a button allowing the webgrid dataset creation.

I have the function to take the row selection and column selection and combine them into a dataset to create the webgrid, but if I cannot get the method to call that routine....

Abhijit Jana22-Jul-09 11:01

Re: Dropdownlist not responding to the "OnSelectedIndexChanged" method.

22-Jul-09 11:01

Then where Dynamic creation of Dropdown list comes into the picture, where as you have three specific dropdown list. if you dont want to show the third one you can make it Visiable=False, and show it when necessary. You need to create dynamic control when you donot need the specific number of control. As fer as I am seeing, There is no need of creation of dynamic control.

cheers,
Abhijit
CodeProject MVP
Web Site:abhijitjana.net
When you ask a question, remember to click "Good Answer", If the Answer is helps you.

Brij22-Jul-09 10:41

Re: Dropdownlist not responding to the "OnSelectedIndexChanged" method.

22-Jul-09 10:41

As Abhijit says can you tell what is your actual requirement?

Cheers!!
Brij

Christian Graus22-Jul-09 11:09

Christian Graus

22-Jul-09 11:09

I would say that the code which you've not posted, as far as I can see, is resetting the content of the other two lists, and thus killing the event.

Christian Graus

Driven to the arms of OSX by Vista.

Read my blog to find out how I've worked around bugs in Microsoft tools and frameworks.

Re: Dropdownlist not responding to the "OnSelectedIndexChanged" method.

TMFoust22-Jul-09 11:18

Re: Dropdownlist not responding to the "OnSelectedIndexChanged" method.

22-Jul-09 11:18

Here is the code behind my page...

public partial class _Default : System.Web.UI.Page
{
    public string study = "";
    public string rowfile = "";
    public string colfile = "";
    public string path = "";
    public string weight = "";
    public TabEngineClass tab;

    protected void Page_Load(object sender, EventArgs e)
    {
        if (this.Page.IsPostBack == false)
        {
          DataSet StudyList = new DataSet();
          StudyList.ReadXml("C:\\WorkingFiles\\TestChartGrid\\TestChartGrid\\StudiesList.xml");
          DropDownList3.DataSource = StudyList;
          DropDownList3.DataValueField = "path";
          DropDownList3.DataTextField = "cycle";
          DropDownList3.DataBind();
        }
    }

    protected void displayDefinitions(object sender, EventArgs e)
    {
        study = DropDownList3.SelectedItem.Text;
        path = DropDownList3.SelectedItem.Value;
        Label1.Visible = true;
        Label2.Visible = true;
        DropDownList1.Visible = true;
        DropDownList2.Visible = true;

        DataSet RowList = new DataSet();
        RowList.ReadXml(path + ".xml");
        DropDownList1.DataSource = RowList;
        DropDownList1.DataValueField = "path";
        DropDownList1.DataTextField = "file";
        DropDownList1.DataBind();
        DataSet ColumnList = new DataSet();
        ColumnList.ReadXml(path + ".xml");
        DropDownList2.DataSource = ColumnList;
        DropDownList2.DataValueField = "path";
        DropDownList2.DataTextField = "file";
        DropDownList2.DataBind();
    }

TMFoust22-Jul-09 11:19

Re: Dropdownlist not responding to the "OnSelectedIndexChanged" method.

22-Jul-09 11:19

Forgot one routine...

protected void nextStep(object sender, EventArgs e)
{
    if (rowfile != "")
    {
        if (colfile != "")
        {
            RadioButtonList1.Visible = true;
        }
        else
        {
            colfile = DropDownList2.SelectedItem.Value + DropDownList2.SelectedItem.Text;
        }
    }
    else
    {
        rowfile = DropDownList1.SelectedItem.Value + DropDownList1.SelectedItem.Text;
    }
}

Christian Graus22-Jul-09 13:37

Christian Graus

22-Jul-09 13:37

Ignoring the sheer idiocy of your naming conventions, have you set breakpoints to step through all this code. Relying on paths to xml files like this for all your data seems very fragile to me.

I notice that that dropdownlist 1 and 2 both are set together, is there not an instance where you set the second list's value and want to update only the value in the third list ?

Christian Graus

Driven to the arms of OSX by Vista.

Read my blog to find out how I've worked around bugs in Microsoft tools and frameworks.

Re: Dropdownlist not responding to the "OnSelectedIndexChanged" method.

TMFoust23-Jul-09 3:28

Re: Dropdownlist not responding to the "OnSelectedIndexChanged" method.

23-Jul-09 3:28

This is a throw-away app to show proof of concept to the upper echelon....

Yes, I have set breakpoints. Dropdownlist1 and 2 both need to have the same source (i.e. the same definition list from the database) because the user has to chose both a row source and a column source for the grid. So, no, there will never be a time that one will key off the other.

The issue I am encountering is that once the code from the displayDefinitions routine runs, none of my subsequent breakpoints gets hit. I can change the selection in DDL1 and DDL2 but it is not triggering the event to call the next Step routine.

TMFoust23-Jul-09 4:43

bar chart graph in asp.net when data is fed from database??

23-Jul-09 4:43

Thanks all.

I found my solution. I had to go a different route to achieve the same effect.

solo_gaurav22-Jul-09 8:55

solo_gaurav

22-Jul-09 8:55

hello friends i need your guidence as soon as possible i want to know how can we draw bar charts using asp.net while the data to bar chart graph is fed from a database
plz buddies help me....really need a way!!!! Frown | :(

Re: bar chart graph in asp.net when data is fed from database??

Brij22-Jul-09 9:09

Re: bar chart graph in asp.net when data is fed from database??

22-Jul-09 9:09

you have several options .you can use microsoft chart controls or any third party chart controls like fusion chart etc.. for the same

Cheers!!
Brij

Abhijit Jana22-Jul-09 9:16