Develop Reference

Strange conflict between get postback control and RegisterStartupScript

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:
<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

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.

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

How to get a radio button excluyent in a repeater element?

I have a repeater using for getting an image nad a radio button on the bottom. I want to achieve a combination of this radio button (repeater speaking) with the property of autoexcluyent feature. How can I achieve it?
As far as I got ...
<asp:Repeater runat="server" ID="repeater1">
<ItemTemplate>
<div class="col-xs-12 col-sm-4 col-md-3">
<asp:Image ID="img" runat="server" ImageUrl="<%#GetRutaImagen(Eval("id").ToString())%>" />
<span>
<asp:RadioButton runat="server" ID="rb1" Text='<%#Eval("description").ToString()%>' GroupName="nameGroup"/>
</span>
</div>
</ItemTemplate>
</asp:Repeater>
With this code I am getting a one radio button per each image but no one autoexcuyent even I am using GroupName property
USING NET FRAMEWORK 4.6.2.

I don't know if easy way to manage this situation however you can manage by below code. It will be good to wrap your contents into update panel so you can prevent page refresh on checkbox changed.
Additionally, IsChecked property being used to initialize checked on page load. You can remove if not required.
.ASPX
<asp:Repeater runat="server" ID="repeater1">
<ItemTemplate>
<div class="col-xs-12 col-sm-4 col-md-3">
<span>
<asp:RadioButton runat="server" ID="rb1" Checked='<%# Eval("IsChecked") %>' AutoPostBack="true" OnCheckedChanged="rb1_CheckedChanged" Text='<%#Eval("description").ToString()%>' />
</span>
</div>
</ItemTemplate>
</asp:Repeater>
.CS
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
List<test1> lst = new List<test1>();
lst.Add(new test1() { Id = 1, description = "R1", IsChecked = false });
lst.Add(new test1() { Id = 3, description = "R2", IsChecked = true });
lst.Add(new test1() { Id = 2, description = "R3", IsChecked = false });
lst.Add(new test1() { Id = 4, description = "R4", IsChecked = false });
repeater1.DataSource = lst;
repeater1.DataBind();
}
}
protected void rb1_CheckedChanged(object sender, EventArgs e)
{
foreach (RepeaterItem item in repeater1.Items)
{
(item.FindControl("rb1") as RadioButton).Checked = false;
}
(sender as RadioButton).Checked = true;
}

After researching between SOF and a few forums I implemented a quite right solution using JS. I am handling another problem related with OnCheckedChanged´s event on RadioButton...
But the initial issue is fixed.
Forum Solution
I am posting the solution that works for me, using as base as a help coming from a forum, hoping it helps others as well with this bug.
REPEATER.
<asp:Repeater runat="server" ID="repeater1" OnItemDataBound="repeater1_ItemDataBound">
<ItemTemplate>
<div class="col-xs-12 col-sm-4 col-md-3">
<asp:Image ID="img" runat="server" ImageUrl="<%#GetRutaImagen(Eval("id").ToString())%>" />
<span>
<asp:RadioButton runat="server" ID="rb1" Text='<%#Eval("description").ToString()%>' GroupName="nameGroup" OnCheckedChanged="rb1_CheckedChanged"/>
</span>
</div>
</ItemTemplate>
</asp:Repeater>
JS
<script>
function SetUniqueRadioButton(nameregex, current) {
for (i = 0; i < document.forms[0].elements.length; i++) {
elm = document.forms[0].elements[i]
if (elm.type == 'radio') {
elm.checked = false;
}
}
current.checked = true;
}
</script>
BACKEND
protected void repeater1_ItemDataBound(object sender, RepeaterItemEventArgs e)
{
try
{
if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
{
RadioButton rbLogoSeleccionado = (RadioButton)e.Item.FindControl("rb1");
string script = "SetUniqueRadioButton('repeater1.*nameGroup',this)";
rbLogoSeleccionado.Attributes.Add("onclick", script);
}
}
catch (Exception ex)
{
PIPEvo.Log.Log.RegistrarError(ex);
throw;
}
}

Session value lost after clicking the button

I use a session to save the hashtable. It has different key-value pairs in it and some of the keys refer to 'List' object.
I have different buttons in the repeater control to change the value of the List and then put it back to hashtable. Then use the same session to save that hashtable. But sometimes the change made get lost in the session. Don't know why. I tried on my test server. It can work fine. While on Prod server, I met this problem.
Any suggestions?
<asp:Repeater ID="rptCountry" runat="server" OnItemDataBound="rptCountry_ItemDataBound" OnItemCommand="rptCountry_ItemCommand">
<ItemTemplate>
<asp:Button ID="btnCountry" runat="server" Text='<%#DataBinder.Eval(Container.DataItem, "Country").ToString() %>' CssClass="iButton Disabled" Enabled="false" UseSubmitBehavior="False" CommandName="Select" />
<asp:Label ID="hdnCountryCode" runat="server" Text='<%#DataBinder.Eval(Container.DataItem, "CountryCode")%>' Visible="false" />
</ItemTemplate>
</asp:Repeater>
protected void rptCountry_ItemCommand(object sender, RepeaterCommandEventArgs e)
{
if (e.CommandName.Equals("Select"))
{
Button btnCountry = (Button)e.Item.FindControl("btnCountry");
Label hdnCountryCode = (Label)e.Item.FindControl("hdnCountryCode");
if (Session["SearchFilter"] != null)
{
Hashtable htSearchFilter = (Hashtable)Session["SearchFilter"];
List<string> countries = (List<string>)htSearchFilter["Country"];
if (countries != null && countries.Count > 0)
{
bool countriesExists = false;
foreach (string country in countries)
{
if (country.Equals(hdnCountryCode.Text.Trim()))
{
countriesExists = true;
}
}
if (!countriesExists)
{
countries.Add(hdnCountryCode.Text.Trim());
btnCountry.CssClass = "iButton Active";
}
else
{
countries.Remove(hdnCountryCode.Text.Trim());
btnCountry.CssClass = "iButton";
}
}
else
{
countries.Add(hdnCountryCode.Text.Trim());
btnCountry.CssClass = "iButton Active";
}
htSearchFilter["Country"] = countries;
Session["SearchFilter"] = htSearchFilter;
ProvinceReloadControl(countries);
}
}
InitControl();
}

How to find control in ListView on Page Load

I am trying to find the formview inside my listview on the page load. However, my result is always null. I called the DataBind method first but still nothing.
Code Behind
protected void Page_Load(object sender, EventArgs e)
{
String list = itemdropdownlist.SelectedValue;
switch (list)
{
case "Section Item":
SectionListView.DataBind();
//SectionListView.Enabled = false;
var temp = (FormView)SectionListView.FindControl("SectionFormView");
temp.Enabled = true;
renderView(SectionListView, "hidden"); // hide listview on page load
break;
}
}
ASP.net code
<InsertItemTemplate>
<tr style="">
<td>
<div style="font-size: .8em;">
<asp:FormView ID="SectionFormView" runat="server" DataKeyNames="SectionItemID" DataSourceID="SectionDataSource">
<ItemTemplate>
<asp:Button ID="InsertButton" runat="server" Text="Insert" OnClick="SectionItemButton_Click" Font-Size="1.2em" />
<asp:Button ID="CancelButton" runat="server" CommandName="Cancel" Text="Clear" Font-Size="1.2em" />
<asp:Label ID="SectionItemLabel" runat="server" Text="SectionItem" Font-Bold="true" Font-Size="1.2em" />
<asp:TextBox ID="SectionItemTextBox" runat="server" />
<asp:Label ID="SectionItemSubLabel" runat="server" Text="SectionItem Label" Font-Bold="true" Font-Size="1.2em" />
<asp:TextBox ID="SectionItemLabelTextBox" runat="server" />
</ItemTemplate>
</asp:FormView>
</div>
</td>
</tr>
</InsertItemTemplate>
<ItemTemplate>

You got that error, because the listview was not binded yet, so i think the best way would be to do all this on the ItemDataBound event. You would find the FormView like:
if (e.Item.ItemType == ListViewItemType.DataItem)
{
FormView SFormView= (FormView)e.Item.FindControl("SectionFormView");
if (SFormView!= null)
{
//code here
}
}

You could use this code to find about anything. I used it before to find Literals that I created in code behind. Use this code to find your FormView
private readonly List<FormView> _foundControls = new List<FormView>();
public IEnumerable<FormView> FoundControls
{
get { return _foundControls; }
}
public void FindChildControlsRecursive(Control control)
{
foreach (Control childControl in control.Controls)
{
if (childControl.GetType() == typeof(FormView))
{
_foundControls.Add((FormView)childControl);
}
else
{
FindChildControlsRecursive(childControl);
}
}
}
FindChildControlsRecursive(<Insert relevent Code Here: Whatever element you want to search inside of like your listView, find that using FindControl>);
FormView[] strControl = new FormView[200];
strControl = FoundControls.ToArray();
foreach (FormView i in strControl)
{
if (i.ID.Equals("< insert controlId of your FormView>"))
{
// do something when you find it
}
}

Data isn't posted in ASP.NET C# in postback using ViewState

I'm trying to post data to the same page after postback with the help of ViewState. I fill out the contents of the page and post the form and display the input on the same page but the validator says that the firstname cannot be null while I just filled out the textbox before I submitted the form.
Default.aspx
<asp:Content ContentPlaceHolderID="Main" runat="server" EnableViewState="true">
<form id="form1" runat="server">
<div>
<table>
<tr>
<td>
<asp:Label ID="lbl1" Text="First Name" runat="server" />
</td>
<td>
<asp:TextBox ID="tFirstName" runat="server" />
</td>
<td>
<asp:RequiredFieldValidator ControlToValidate="tFirstName" ErrorMessage="This field cannot be empty."
runat="server" />
</td>
</tr>
<tr>
<td>
<asp:Label ID="lbl2" Text="Last Name" runat="server" />
</td>
<td>
<asp:TextBox ID="tLastName" runat="server" />
</td>
</tr>
</table>
</div>
<asp:Button ID="id" Text="Submit" runat="server" OnClick="Submit" />
<div>
<p>
<asp:Label ID="lTest" runat="server" /></p>
</div>
<asp:Label ID="lSubmit" runat="server" />
</form>
Default.aspx.cs
protected void Page_Load(object sender, EventArgs e)
{
if (Page.IsPostBack)
{
tFirstName.Text = (string)ViewState["tFirstName"];
tLastName.Text = (string)ViewState["tLastName"];
}
else
{
ViewState["tFirstName"] = tFirstName.Text;
ViewState["tLastName"] = tLastName.Text;
}
}
protected void Submit(object sender, System.EventArgs args)
{
try
{
lTest.Text = tFirstName.Text + " " tLastName.Text;
}
catch (Exception ex)
{
throw;
}
}

It seems my logic was wrong. The correct condition should be Page_Load() function:
if (!Page.IsPostBack)
{
tFirstName.Text = (string)ViewState["tFirstName"];
tLastName.Text = (string)ViewState["tLastName"];
}

It should be if (!Page.IsPostBack) instead of if (Page.IsPostBack)
:D
Have fun!

You are getting too confuse on this,
Below is the possible way to solve your issues. Before this, please learn about postback in page load
Seems you are passing the null values to the ViewState,
if (Page.IsPostBack)
{
tFirstName.Text = (string)ViewState["tFirstName"];
tLastName.Text = (string)ViewState["tLastName"];
}
else
{
ViewState["tFirstName"] = tFirstName.Text;
ViewState["tLastName"] = tLastName.Text;
}
Proceed as following
protected void Page_Load(object sender, EventArgs e)
{
if(IsPostback==true)
{
if(ViewState["tFirstName"]!=null && ViewState["tLastName"]!=null)
{
tFirstName.Text = (string)ViewState["tFirstName"];
tLastName.Text = (string)ViewState["tLastName"];
}
}
}
protected void Submit(object sender, System.EventArgs args)
{
try
{
ViewState["tFirstName"] = tFirstName.Text;
ViewState["tLastName"] = tLastName.Text;
lTest.Text = tFirstName.Text + " " tLastName.Text;
}
catch (Exception ex)
{
throw;
}
}

I only want to point out, that you do NOT have to reassign values to the textboxes after a Postback. This is the normal asp.net web control behavior when EnableViewstate is turned on.
Remove your code from Page_Load and you should notice that textboxes remember values after a postback (unless you specifically remove it in behind code like tFirstName.Text = "")