Question

I am dynamically adding a custom user control to an update panel. My user control contains two dropdownlists and a textbox. When a control outside of the update panel triggers a postsback, I am re-adding the user control to the update panel.

The problem is…on postback when I re-add the user controls, it’s firing the “SelectedIndexChanged” event of the dropdownlists inside the user control. Even if the selectedindex did not change since the last postback.

Any ideas?

I can post the code if necessary, but there’s quite a bit in this particular scenario.

Thanks in advance!

EDIT…CODE ADDED BELOW

*.ASCX

<asp:DropDownList ID="ddlColumns" OnSelectedIndexChanged="ddlColumns_SelectedChanged" AppendDataBoundItems="true" AutoPostBack="true" runat="server">

*.ASCX.CS

List<dataColumnSpecs> dataColumns = new List<dataColumnSpecs>();

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        fillDDLColumns();
    }        
}

public void fillDataColumnsList()
{
    dataColumns.Clear();
    //COMMON GETDATATABLE RETURNS A DATA TABLE POPULATED WITH THE RESULTS FROM THE STORED PROC COMMAND
    DataTable dt = common.getDataTable(storedProcs.SELECT_COLUMNS, new List<SqlParameter>());
    foreach (DataRow dr in dt.Rows)
    {
        dataColumns.Add(new dataColumnSpecs(dr["columnName"].ToString(), dr["friendlyName"].ToString(), dr["dataType"].ToString(), (int)dr["dataSize"]));
    }
}

public void fillDDLColumns()
{
    fillDataColumnsList();
    ddlColumns.Items.Clear();
    foreach (dataColumnSpecs dcs in dataColumns) 
    { 
        ListItem li = new ListItem(); 
        li.Text = dcs.friendlyName; 
        li.Value = dcs.columnName; 
        ddlColumns.Items.Add(li);
    }
    ddlColumns.Items.Insert(0, new ListItem(" -SELECT A COLUMN- ", ""));
    ddlColumns.DataBind();  
}

protected void ddlColumns_SelectedChanged(object sender, EventArgs e)
{
    //THIS CODE IS BEING FIRED WHEN A BUTTON ON THE PARENT *.ASPX IS CLICKED
}

*.ASPX

<asp:UpdatePanel ID="upControls" runat="server">
    <ContentTemplate>
        <asp:Button ID="btnAddControl" runat="server" Text="+" OnClick="btnAddControl_Click" />
    </ContentTemplate>
</asp:UpdatePanel>
<asp:Button ID="btnGo" runat="server" Text="Go" OnClick="btnGo_Click" ValidationGroup="vgGo" />
<asp:GridView...

*.ASPX.CS

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        uc_Counter = 0;
        addControl();
        gridview_DataBind();
    }
    else
    {
        reloadControls();
    }
}

protected void btnGo_Click(object sender, EventArgs e)
{
    if (Page.IsValid)
    {
        //THIS BUTTON CLICK IS WHAT'S TRIGGERING THE 
        //SELECTEDINDEXCHANGED EVENT TO FIRE ON MY *.ASCX
        gridview_DataBind();
    }   
}

private void reloadControls()
{
    int count = this.uc_Counter;

    for (int i = 0; i < count; i++)
    {
        Control myUserControl = Page.LoadControl("~/Controls/myUserControl.ascx");
        myUserControl.ID = "scID_" + i;
        upControls.ContentTemplateContainer.Controls.AddAt(i, myUserControl);
        ((customUserControl)myUserControl).fillDDLColumns();
    }
}

private void addControl()
{
    Control myUserControl = Page.LoadControl("~/Controls/myUserControl.ascx");
    myUserControl.ID = "scID_" + uc_Counter.ToString();
    upControls.ContentTemplateContainer.Controls.AddAt(upControls.ContentTemplateContainer.Controls.IndexOf(btnAddControl), myUserControl);            
    //((customUserControl)myUserControl).fillDDLColumns();
    this.uc_Counter++;
}

protected int uc_Counter
{
    get { return (int)ViewState["uc_Counter"]; }
    set { ViewState["uc_Counter"] = value; }
}

Answer 1

I found my answer in this post .net DropDownList gets cleared after postback

I changed my counter that I was storing in the viewstate to a session variable.
Then I moved my reloadControls() function from the Page_Load of the *.ASPX to the Page_Init.

The key was dynamically adding my user control in the Page_Init so it would be a member of the page before the Viewstate was applied to controls on the page.