• Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 414
  • Last Modified:

Problems with Dropdownlist and postback

I am populating a page with user controls dynamically. One of the control two dropdownlists. Once you make a selection in the first dropdown it populates the second. Here is the problem it only works on the second try. When you make a selection the first time it posts back, but no results are returned, if you try again, it works perfectly. I will post some code in the hopes that someone can help me find an answer.

as always I appreciate your help.
CJSantora

aspcx:

    <tr>
        <td align="left"><asp:Label ID="lblSearchManufacturers" runat="server" Text="Search By Manufacturer"></asp:Label></td>
        <td style="width: 81px" align="left"><asp:DropDownList ID="cboMakes" DataTextField="name" DataValueField="Makeid" runat="server" AutoPostBack=true Width="200px" OnSelectedIndexChanged="cboMakes_SelectedIndexChanged"></asp:DropDownList></td>
    </tr>
    <tr>
        <td align="left"><asp:Label ID="lblSearchByModel" runat="server" Text="Search By Model" Width="149px"></asp:Label></td>
        <td style="width: 81px" align="left"><asp:DropDownList ID="cboModels" DataTextField="name" DataValueField="modelid" runat="server" Width="200px"></asp:DropDownList></td>
    </tr>

code bhind:

public partial class includes__public_pubQuicktruckLocator : System.Web.UI.UserControl
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Page.SetFocus(cboMakes);
        populateMakes(0);
    }

    protected void cboMakes_SelectedIndexChanged(object sender, EventArgs e)
    {  
        int intmakeid = 0;            
        intmakeid = Convert.ToInt32(cboMakes.SelectedItem.Value);

        Response.Write(intmakeid);
        Response.Write(sender.ToString() + "<br>");
        Response.End();

        populateMakes(intmakeid);
        populateModels(intmakeid);
    }


    private void populateMakes(int intmakeid)
    {        
        cboMakes.DataSource = data.GetUniqueTrucksFromAds();
        cboMakes.DataBind();
        cboMakes.Items.Insert(0,new ListItem("All Makes","0"));
        cboMakes.Items.FindByValue(intmakeid.ToString()).Selected = true;
    }

    private void populateModels(int intmakeid)
    {
        cboModels.DataSource = data.GetUniqueTruckModelsFromAds(intmakeid);
        cboModels.DataBind();
        cboModels.Items.Insert(0, new ListItem("All Models", "0"));
    }

    protected void cmdQuickSearch_Click(object sender, ImageClickEventArgs e)
    {
        int intmakeid = 0;
        int intmodelid = 0;

        if (Convert.ToInt32(e.X) != 0 && Convert.ToInt32(e.Y) != 0)
        {

            if (cboMakes.SelectedIndex != 0)
            {
                intmakeid = Convert.ToInt32(cboMakes.SelectedItem.Value);
            }
            if (cboModels.SelectedIndex != 0)
            {
                intmodelid = Convert.ToInt32(cboModels.SelectedItem.Value);
            }
            Response.Redirect("~/default.aspx?pg=results&make=" + intmakeid + "&model=" + intmodelid);
        }
    }

}
0
CJSantora
Asked:
CJSantora
  • 5
  • 4
1 Solution
 
dstanley9Commented:
in this case, you don't need to DataBind() the Makes on each call.  In fact, re-binding the data will cause you to lose your SelectedItem value. try:

    protected void Page_Load(object sender, EventArgs e)
    {
        Page.SetFocus(cboMakes);
        if(!IsPostBack)
          populateMakes(0);
    }
0
 
CJSantoraAuthor Commented:
I really appreciate your feedback dstanley9. I tried your suggestion, however the dropdownlist does not populate under this condition. The control is activated by a tabbed imagemap, so I think when you click on the tab to display the truck search it causes a postback and this is why there was no data bound to the control.


CJSantora
0
 
dstanley9Commented:
Can you move the code:

          populateMakes(0);

to the event hadler fired when the tab is selected?
0
Free Tool: Site Down Detector

Helpful to verify reports of your own downtime, or to double check a downed website you are trying to access.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

 
CJSantoraAuthor Commented:
I am not sure if that is a possibility or not, I will look into it. I have an additional question, and this may be a strech, but can you determine if the Postback was from a specific user control?

CJSantora
0
 
dstanley9Commented:
I've never tried it myself, but you can try this method:

http://www.eggheadcafe.com/articles/20050609.asp
0
 
CJSantoraAuthor Commented:
I thought I would post an additional finding that may offer some new ideas. The drowdownlist is using OnSelectedIndexChanged="cboMakes_SelectedIndexChanged to trigger the population of the next dropdownlist. I have determined that this is not happening on the first post, can anyone think of any reasons that the page would not see the OnSelectedIndexChanged="cboMakes_SelectedIndexChanged?

CJSantora
0
 
dstanley9Commented:
IIRC, When you re-bind a control in Page_Load, it "clears" any events that would be triggered by the control (including SelectedIndexChanged).  That is one reason why you don't re-bind unless the request is not a post back.
0
 
CJSantoraAuthor Commented:
I remmber you stating that in an earlier post and I continued trying to modify the code to eliminate that possibility. The code that is currently being executed does not do a second databind, but still does not return the proper id from the dropdownlist on the first post;

    protected void Page_Load(object sender, EventArgs e)
    {
        //Response.Write(cboMakes.Items.Count + "<br>");
        if (cboMakes.Items.Count == 0)
        {
            populateMakes();
        }
        else
        {
            populateModels();
        }

    }

    private void populateMakes()
    {        
        cboMakes.DataSource = data.GetUniqueTrucksFromAds();
        cboMakes.DataBind();
        cboMakes.Items.Insert(0, new ListItem("All Makes", "0"));
    }

    protected void cboMakes_SelectedIndexChanged(object sender, EventArgs e)  // NOT BEING CALLED AT ALL NOW
    {
        Response.Write("Index Changed");
        populateModels();
    }

    private void populateModels()
    {

        int intmakeid = 0;
        intmakeid = Convert.ToInt32(cboMakes.Selecteditem.Value);  // IS ALWAYS RETURNING ZERO ON FIRST PASS
        Response.Write(intmakeid);

        cboModels.DataSource = data.GetUniqueTruckModelsFromAds(intmakeid);
        cboModels.DataBind();
        cboModels.Items.Insert(0, new ListItem("All Models", "0"));
    }

    protected void cmdQuickSearch_Click(object sender, ImageClickEventArgs e)
    {
        int intmakeid = 0;
        int intmodelid = 0;

        if (Convert.ToInt32(e.X) != 0 && Convert.ToInt32(e.Y) != 0)
        {

            if (cboMakes.SelectedIndex != 0)
            {
                intmakeid = Convert.ToInt32(cboMakes.SelectedItem.Value);
            }
            if (cboModels.SelectedIndex != 0)
            {
                intmodelid = Convert.ToInt32(cboModels.SelectedItem.Value);
            }
            Response.Redirect("~/default.aspx?pg=results&make=" + intmakeid + "&model=" + intmodelid);
        }
    }

I really appreciate your help.
CJSantora
0
 
dstanley9Commented:
I think you may have PopulateModels() in the wrong spot:  try:

    protected void Page_Load(object sender, EventArgs e)
    {
        //Response.Write(cboMakes.Items.Count + "<br>");
        if (cboMakes.Items.Count == 0)
        {
            populateMakes();
        }
        else
        {
            //do not populate here as it will be populated when the make index changes
            //populateModels();
        }

    }
0

Featured Post

Hire Technology Freelancers with Gigs

Work with freelancers specializing in everything from database administration to programming, who have proven themselves as experts in their field. Hire the best, collaborate easily, pay securely, and get projects done right.

  • 5
  • 4
Tackle projects and never again get stuck behind a technical roadblock.
Join Now