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Strange conflict between get postback control and RegisterStartupScript – Asp.net

Please consider this scenario:

I have a simple page and I want to log all controls causing postback. I create this simple page. It contains a grid to show some URLs and when user click on an icon a new tab should open:

enter image description here

<form id="form1" runat="server">
<div>
        <table style="width: 100%;">
            <tr>
                <td style="background-color: #b7ffbb; text-align: center;" colspan="2">
                    <asp:Button ID="Button3" runat="server" Text="Click Me First" Height="55px" OnClick="Button3_Click" />
                </td>
            </tr>
            <tr>
                <td style="background-color: #f1d8fe; text-align: center;" colspan="2">
                    <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" BackColor="White" OnRowCommand="GridView1_RowCommand">
                        <Columns>
                            <asp:BoundField DataField="SiteAddress" HeaderText="Address" />
                            <asp:TemplateField>
                                <ItemTemplate>
                                    <asp:ImageButton ID="ImageButton1" ImageUrl="~/download.png" runat="server" CommandArgument='<%# Eval("SiteAddress") %>' CommandName="GoTo" Height="32px" Width="32px" />
                                </ItemTemplate>
                            </asp:TemplateField>
                        </Columns>
                    </asp:GridView>
                </td>
            </tr>
        </table>
    </div>
</form>

and code behind:

public partial class WebForm2 : Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    protected void Button3_Click(object sender, EventArgs e)
    {
        List<Address> Addresses = new List<Address>()
        {
            new Address(){ SiteAddress = "https://google.com" },
            new Address(){ SiteAddress = "https://yahoo.com" },
            new Address(){ SiteAddress = "https://stackoverflow.com" },
            new Address(){ SiteAddress = "https://learn.microsoft.com/}" }
        };

        GridView1.DataSource = Addresses;
        GridView1.DataBind();
    }

    protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        ScriptManager.RegisterStartupScript(this, this.GetType(), "MyScript", "window.open('" + e.CommandArgument.ToString() + "', '_blank')", true);
    }
}

class Address
{
    public string SiteAddress { get; set; }
}

every thing is fine till here. Now I create a base class for all of my pages and add below codes for finding postback control:

public class MyPageBaseClass : Page
{
    protected override void OnInit(EventArgs e)
    {
        if (!IsPostBack)
        {
            
        }
        else
        {
            var ControlId = GetPostBackControlName();   <------
            //Log ControlId 
        }
        base.OnInit(e);
    }

    private string GetPostBackControlName()
    {
        Control control = null;

        string ctrlname = Page.Request.Params["__EVENTTARGET"];
        if (ctrlname != null && ctrlname != String.Empty)
        {
            control = Page.FindControl(ctrlname);
        }

        else
        {
            foreach (string ctl in Page.Request.Form)
            {
                Control c;
                if (ctl.EndsWith(".x") || ctl.EndsWith(".y"))
                {
                    string ctrlStr = ctl.Substring(0, ctl.Length - 2);
                    c = Page.FindControl(ctrlStr);
                }
                else
                {
                    c = Page.FindControl(ctl);
                }
                if (c is System.Web.UI.WebControls.Button ||
                         c is System.Web.UI.WebControls.ImageButton)
                {
                    control = c;
                    break;
                }
            }

        }

        if (control != null)
            return control.ID;
        else
            return string.Empty;
    }
}

and change this line:

public partial class WebForm2 : MyPageBaseClass

Now when I click on icons grid view disappears…(STRANGE…) and nothing happened. When I comment specified line then every thing will be fine…(STRANGE…).

In GetPostBackControlName nothings changed to Request but I don’t know why this happened. I checked and I see if I haven’t RegisterStartupScript in click event every thing is fine. Please help we to solve this problem.
Thanks

Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    The problem is related to OnInit event. I replaced it with OnPreLoad and every things is fine now.

    For search engines: OnInit event has conflict with RegisterStartupScript


  2. 0

    when I click on icons grid view disappears…

    ASP.Net page class object instances only live long enough to serve one HTTP request, and each HTTP request rebuilds the entire page by default.

    Every time you do a postback, you have a new HTTP request and therefore a new page class object instance and a completely new HTML DOM in the browser. Any work you’ve done for a previous instance of the page class — such as bind a list of addresses to a grid — no longer exists.

    You could fix this by also rebuilding your grid code on each postback, but what I’d really do is skip the whole "RegisterStartupScript" mess and instead make the grid links open the window directly, without a postback at all.

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