dropdownlist postback not firing

Discussion in 'ASP .Net' started by =?iso-8859-1?B?R2VhcvNpZA==?=, Mar 5, 2007.

  1. =?iso-8859-1?B?R2VhcvNpZA==?=, Mar 5, 2007
    #1
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  2. =?Utf-8?B?TWlsb3N6IFNrYWxlY2tpIFtNQ0FEXQ==?=, Mar 5, 2007
    #2
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  3. Strange

    I have tried the following

    <asp:DropDownList ID="DropDownListMake" runat="server"
    CssClass="selectComparison" AutoPostBack="True"
    OnSelectedIndexChanged="DropDownListMake_SelectedIndexChanged" >
    <asp:ListItem>1</asp:ListItem>
    <asp:ListItem>2</asp:ListItem>
    <asp:ListItem>3</asp:ListItem>
    </asp:DropDownList>

    --------

    protected void DropDownListMake_SelectedIndexChanged(object
    sender,EventArgs e)
    {
    int x ;

    if (!DropDownListMake.SelectedIndex.Equals("-1"))
    x = Int32.Parse(DropDownListMake.SelectedValue);
    }

    --------

    and it did work
    perhaps the AutoPostBack="True"
    doesn't fire if the DDL isn't bound to any data

    -------------------------------------------
    If my answer helped you please press "Yes" bellow

    Adlai Maschiach
    http://blogs.microsoft.co.il/blogs/adlaim/


    "Gearóid" wrote:

    > Sorry to repost, but please see below... this is driving me mad at
    > this point.
    >
    > http://groups.google.com/group/micr...4de068d5333/55a7318a2f318442#55a7318a2f318442
    >
    >
     
    =?Utf-8?B?QWRsYWkgTWFzY2hpYWNo?=, Mar 5, 2007
    #3
  4. The bizarre thing is the AutoPostBack="True" does fire. If I place a
    breakpoint in my code on the Page_Load it is hit after I select
    something in the DropDownList. But when it hitsthe line to see if
    it's a postback or not it says it isn't. If I hover over if(!
    this.IsPostBack) it tells me IsPostBack is false.

    So even the the postback has fired and the breakpoint has been
    triggered in my Page_load method, it thinks it's not a postback.
    That's what baffles me...

    snippet of Page_Load to bind data...

    protected void Page_Load(object sender, EventArgs e)
    {
    if (!this.IsPostBack)
    {
    LoadMakes();
    }
    else // postback
    {
    nMakeID = int.Parse(DropDownListMake.SelectedValue);
    }
    }


    private void LoadMakes()
    {
    DataTable dtMakes = new NewBike().GetMakes("Bike");

    ClearDropDowns(true, true);
    PopulateDropDown(DropDownListMake, dtMakes, "makeid", "makename",
    "Make");
    }

    private void PopulateDropDown(DropDownList ddlList, DataTable dtData,
    string strValueField, string strTextField, string strDefaultPromt)
    {
    ddlList.DataSource = dtData;
    ddlList.DataValueField = strValueField;
    ddlList.DataTextField = strTextField;
    ddlList.DataBind();
    ddlList.Items.Insert(0, new ListItem("Choose " + strDefaultPromt,
    "-1"));
    ddlList.SelectedIndex = 0;
    }
     
    =?iso-8859-1?B?R2VhcvNpZA==?=, Mar 5, 2007
    #4
  5. Hi

    each time you populate a DDL ( or every other control )
    it's previous ViewState is Cleared/Ignored
    that may be the cause for that
    the SelectedIndexChange isn't fired
    becuse according to the Page the contence has
    change , thus irrelevant ( even if it's contence is the same )

    -------------------------------------------


    If my answer helped you please press "Yes" bellow

    Adlai Maschiach
    http://blogs.microsoft.co.il/blogs/adlaim/


    "Gearóid" wrote:

    > The bizarre thing is the AutoPostBack="True" does fire. If I place a
    > breakpoint in my code on the Page_Load it is hit after I select
    > something in the DropDownList. But when it hitsthe line to see if
    > it's a postback or not it says it isn't. If I hover over if(!
    > this.IsPostBack) it tells me IsPostBack is false.
    >
    > So even the the postback has fired and the breakpoint has been
    > triggered in my Page_load method, it thinks it's not a postback.
    > That's what baffles me...
    >
    > snippet of Page_Load to bind data...
    >
    > protected void Page_Load(object sender, EventArgs e)
    > {
    > if (!this.IsPostBack)
    > {
    > LoadMakes();
    > }
    > else // postback
    > {
    > nMakeID = int.Parse(DropDownListMake.SelectedValue);
    > }
    > }
    >
    >
    > private void LoadMakes()
    > {
    > DataTable dtMakes = new NewBike().GetMakes("Bike");
    >
    > ClearDropDowns(true, true);
    > PopulateDropDown(DropDownListMake, dtMakes, "makeid", "makename",
    > "Make");
    > }
    >
    > private void PopulateDropDown(DropDownList ddlList, DataTable dtData,
    > string strValueField, string strTextField, string strDefaultPromt)
    > {
    > ddlList.DataSource = dtData;
    > ddlList.DataValueField = strValueField;
    > ddlList.DataTextField = strTextField;
    > ddlList.DataBind();
    > ddlList.Items.Insert(0, new ListItem("Choose " + strDefaultPromt,
    > "-1"));
    > ddlList.SelectedIndex = 0;
    > }
    >
    >
     
    =?Utf-8?B?QWRsYWkgTWFzY2hpYWNo?=, Mar 5, 2007
    #5
  6. Thanks for your help. I got this sorted.

    I have the following method

    protected override object LoadPageStateFromPersistenceMedium()
    {

    LosFormatter Format = new LosFormatter();
    //return Format.Deserialize (Request.Form["__VIEWSTATE"]);
    string strSession = "";

    if (Session["_ViewState"] != null)
    {
    strSession = Session["_ViewState"].ToString();
    return Format.Deserialize(strSession);
    }
    else
    {
    return null;
    }
    }

    This was being called in a basepage. Before it was called the
    postback was there, but after it executed it was lost. It appears
    this was clearing my viewstate, and in turn losing my postback
     
    =?iso-8859-1?B?R2VhcvNpZA==?=, Mar 5, 2007
    #6
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