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FindControl() always returns null from DataList Textbox

I have 8 items in a SQL table with a Description, ItemNumber, and ImagePath.
protected void Page_Load(object sender, EventArgs e)
{
//fill the datalist for the Signs Table
string tCallFrom = "Program." + System.Reflection.MethodBase.GetCurrentMethod().Name;
string tQry = #"SELECT * FROM [js_Signs]";
DataTable tblSigns = objCommMethods.fReturnTableFromQry(clsDBSelect.enumDBSelect.ProjectMaster, tQry, tCallFrom);
SignsList.DataSource = tblSigns;
SignsList.DataBind();
}
I am using a DataList to show all of the items along with a textbox that will allow a user to input the number of items they want:
<asp:DataList ID="SignsList" runat="server" RepeatColumns="4" CellPadding="2" Width="90%" ItemStyle-HorizontalAlign="Center">
<ItemTemplate>
<table>
<tr>
<th>
<%#DataBinder.Eval(Container.DataItem, "Description") %>
</th>
</tr>
<tr>
<th>
<%#DataBinder.Eval(Container.DataItem, "ItemNumber") %>
</th>
</tr>
<tr>
<td>
<asp:Image ID="SignImage" runat="server" ImageUrl='<%#DataBinder.Eval(Container.DataItem, "ImagePath") %>' />
</td>
</tr>
<tr style="text-align: center;">
<td>
<asp:TextBox ID="txtSignQuantity" runat="server" CssClass="txtBox" BackColor="White" Enabled="true"
type="number" min="0" ToolTip="Please choose quantity of signs needed."/>
</td>
</tr>
<tr>
<td>
<p> </p>
</td>
</tr>
</table>
</ItemTemplate>
</asp:DataList>
<div class="btnGroup">
<div class="btnDiv">
<asp:Button ID="btnSave" runat="server" Text="Save" CssClass="btnSave" Width="90px" Visible="true" OnClick="btnSave_Click"/>
</div>
<div class="btnDiv">
<asp:Button ID="btnCancel" runat="server" Text="Clear" CssClass="btnCancel" Width="90px" Visible="true" OnClick="btnCancel_Click"/>
</div>
</div>
After the saved button is clicked in C# I want to find out the value that a user entered but it is always returning null:
protected void btnSave_Click(object sender, EventArgs e)
{
TextBox txtSignQuantity;
string tempSignQuantity;
try
{
foreach (DataListItem item in SignsList.Items)
{
txtSignQuantity = item.FindControl("txtSignQuantity") as TextBox;
tempSignQuantity = txtSignQuantity.Text;
}
}
catch (Exception ex)
{
Console.WriteLine(ex);
}
}
I also checked and the Count of SignsList.Items was 8, so I know that it is retrieving the correct information. Sorry, I've never used a Data List before so I'm not really sure how to go about this...

The short answer is that data binding on postback is causing the problem. Check the Page.IsPostBack property before doing data binding:
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
//fill the datalist for the Signs Table
string tCallFrom = "Program." + System.Reflection.MethodBase.GetCurrentMethod().Name;
string tQry = #"SELECT * FROM [js_Signs]";
DataTable tblSigns = objCommMethods.fReturnTableFromQry(clsDBSelect.enumDBSelect.ProjectMaster, tQry, tCallFrom);
SignsList.DataSource = tblSigns;
SignsList.DataBind();
}
}
ASP.NET WebForms attempts to abstract away the fact that the control instances that were used to render the page are not the same instances it has when handling postback events. Data binding compounds the abstraction because it has to create controls in response to the DataBind call, and then on postback, recreate them based on the ViewState it saved.
Initializing controls from ViewState happens on the Init event, so when the Load event is fired later in the page lifecycle and you call DataBind on the control, everything it restored gets wiped out and recreated.
As for why you were getting null, it may have been that the controls were wiped out but not recreated; it may have had to do with other event handlers that didn't get rewired after the second data binding.

Disable asp imagebutton

I am trying to get the image button in this table to get hidden via the code behind in C# (so that I can hide it after an action).
<asp:UpdatePanel runat="server" ID="upEmpListContainer" UpdateMode="Conditional"
OnPreRender="upEmpListContainer_PreRender" OnInit="upEmpListContainer_Oninit">
<ContentTemplate>
<asp:ListView ID="lvEmpList" OnItemDataBound="lvEmpList_ItemDataBound" OnDataBound="lvEmpList_DataBound"
OnLayoutCreated="lvEmpList_LayoutCreated" runat="server" OnPreRender="lvEmpList_PreRender">
<LayoutTemplate>
<table class="formData_tb" cellspacing="0" style="margin: 0px; width: 100%;">
<tr>
<th colspan="9" class="currentManagerLabel" style="text-align: center">
<span>Currently displaying
<asp:Label ID="lblManager" runat="server" />
employees </span>
<asp:ImageButton ID="DrillUp" AlternateText="Move up in reporting heirarchy" runat="server"
CommandName="DrillDown" ImageUrl="~/images/icoDoubleArrowUp.gif" OnCommand="butDrillDown_Click" />
</th>
</tr>
</table>
</LayoutTemplate>
</asp:ListView>
</ContentTemplate>
</asp:UpdatePanel>
I just can't seem to access it from its ID. I've tried DrillUp.Enabled = false; but Visual Studio is saying that it can't resolve symbol 'DrillUp'.

Your imagebutton is inside layout template, you cant access it directly.
Try this
ImageButton b = (ImageButton)lvEmpList.FindControl("DrillUp");
b.Visible = false;

In your code behind method lvEmpList_ItemDataBound, you need to use the following:
((e.Item.FindControl("DrillUp")) as ImageButton).Visible = false;
Also, you should add a check that this is done only for the DataItem items like this:
if (e.Item.ItemType == ListViewItemType.DataItem)
{
((e.Item.FindControl("DrillUp")) as ImageButton).Visible = false;
}

Try to:
1-remove that imagebutton from aspx
1-clean the solution
2- Write manually again that asp:imagebutton...
It will work fine

Text box getting cleared because of update panel

I've have one table, in that table within one I've one and within that , I've update panel whose update mode is set to conditional. Within this update panel I've another table. The table contains 3 text boxes as: old password, new password and confirm password. On the textChanged event of the old password I am checking the user entered value with the value in db. But when the function completes its execution all the 3 text boxes looses its values regardless of whether I update the update panel or not. I don't know why it clears text boxes. I want to prevent text boxes from getting cleared. I tried to get the text box text in string variable and again assign it to text boxes (both in text box text changed event and in page load event under isPostBack condition) but its too, not working.
asp code:
.
.
.
<tr>
<td colspan="3">
<div>
<asp:UpdatePanel ID="updPnlChngPwd" runat="server" UpdateMode="Conditional">
<ContentTemplate>
<table style="width:100%">
<tr>
<td>
Old Password
</td>
<td>:</td>
<td>
<asp:TextBox ID="txtOldPwd" runat="server" Height="21px" MaxLength="50" TextMode="Password" Width="60%" ontextchanged="txtOldPwd_TextChanged"
AutoPostBack="True"></asp:TextBox>
</td>
</tr>
<tr>
<td></td>
<td></td>
<td>
<asp:Label ID="lblWrongOldPwd" runat="server" Text="Wrong Old Password" ForeColor="Red" Visible="False"></asp:Label>
</td>
</tr>
<tr>
<td>
Password
</td>
<td>:</td>
<td></td>
</tr>
<tr>
<td></td>
<td>:</td>
<td>
<asp:TextBox ID="txtSuppRePwd" runat="server" Height="21px" MaxLength="50" TextMode="Password" Width="60%"></asp:TextBox>
</td>
</tr>
<tr>
<td></td>
<td>
<asp:Button ID="btnUpdPwd" runat="server" Text="Change Password" onclick="btnUpdPwd_Click"/></td>
<td>
</td>
</tr>
</table>
</ContentTemplate>
</asp:UpdatePanel>
</div>
<td>
</tr>
.
.
.
C# code for tetxt box textChanged event:
protected void txtOldPwd_TextChanged(object sender, EventArgs e)
{
DataTable dtOldPwd = Obj.DBAccess("select Pwd from Customer where Cust_Id = " + Convert.ToInt32(Session["SuppID"]) + " and Supp_Pwd = '" + txtOldPwd.Text + "'");
if (dtOldPwd.Rows.Count == 1)
{
lblWrongOldPwd.Visible = false;
}
else
{
lblWrongOldPwd.Visible = true;
updPnlChngPwd.Update();
}
}
Now I am not able to understand what exactly wrong I am doing, does having update panel inside the table causing problem?

<td>
<asp:TextBox ID="txtSuppRePwd" runat="server" Height="21px" MaxLength="50" TextMode="Password" Width="60%"></asp:TextBox>
</td>
You have TextMode set to password which will not save your textbox value .
However you will get your textbox value as string on textchange event
protected void txtbx_TextChanged(object sender, EventArgs e)
{
string txtValue = txtbx.Text;
ViewState["xyz"]= txtValue;
}
and you have to save this value in ViewState to use it for btnClick event .
OR
You can also set textbox attribute at Page_Load event which is a very bad practice to do like this
protected void Page_Load(object sender, EventArgs e)
{
txtbx.Attributes.Add("value", txtbx.Text);

TextBox with TextMode="Password" will be cleared after postback or partial postback. This is the default behavior of the password textbox so submit all the data at a time and do the validation in your code.
Alternatively, You can store password in in viewstate or session and restore after postback.

textbox not displaying in code behind c# file

I have a sales simulator written in C#. I did not write this however I am currently modifying it to suit different requirements.
It basically displays a list of products from a database, and has a textbox for each product where you can enter in the quantity sold. The quantity sold is calculated based on it's price in the database.
Now it's all working fine, however there is one SMALL issue. When "Buy" is clicked, it returns me back to the list of products which IS correct, however the quantity I have entered for the previous product remains.
I would like to know how to restore the text boxes to their default value when the after the data is submitted to the database.
I always thought the way to do this would be in the .cs code behind file
txtQuantity.Text = "";
However, for some odd reason, txtQuantity will not show up.
Can anyone think of anything I am doing wrong? Here is a snippet of code from the aspx file.
<form id="form1" runat="server">
Date:
<asp:TextBox ID="txtDate" runat="server" />
Retailer:
<asp:DropDownList ID="dlStore" runat="server"
onselectedindexchanged="dlStore_SelectedIndexChanged" />
<asp:ListView ID="lbProducts" runat="server">
<LayoutTemplate>
<layouttemplate>
<table border="1" cellpadding="1" style="width:800px">
<tr style="background-color:#E5E5FE">
<th>ID</th>
<th>ProductCode</th>
<th>Product Title</th>
<th>RRP $</th>
<th>Quantity</th>
<th>Sale Price $</th>
</tr>
<tr id="itemPlaceholder" runat="server"></tr>
</table>
</layouttemplate>
</LayoutTemplate>
<ItemTemplate>
<tr>
<td style="width: 50px;">
<%#Eval("ProductID") %>
</td>
<td>
<%#Eval("ProductCode") %>
</td>
<td>
<%#Eval("ProductTitle") %>
</td>
<td>
<%#Eval("USListPrice") %>
</td>
<td style="width: 50px;">
<asp:TextBox ID="txtQuantity" runat="server" Text="0" />
</td>
<td style="width: 50px;">
<asp:TextBox ID="txtSalePrice" runat="server" Text="0.00" />
</td>
</tr>
</ItemTemplate>
</asp:ListView>
<asp:Button ID="btnBuy" Text="Buy These Items" runat="server" OnClick="btnBuy_Click" />
<asp:Button ID="btnClear" Text="Clear Existing Sales" runat="server"
onclick="btnClear_Click" />
</form>
There's a lot going on in the code behind file and I wouldn't expect anyone to go through it, but how I collect the data from txtQuantity is done with the following line of code:
Int32 quantity = Int32.Parse(((TextBox)item.FindControl("txtQuantity")).Text);
So what I want to be able to do is set this textbox either to be empty, or back to zero.
Any help is appreciated, thanks.

Because that txtQuantity control is within a ListView, there could be any number of instances of that control generated. So you can't access all of them through a single variable.
You will need to look through all controls within that ListView (and several levels deep) to find all your txtQuantity controls.
The same of course for the txtSalePrice control.
EDIT
You could find those textboxes with code like (untested)
public IEnumerable<TextBox> FindTextBoxes(Control parent)
{
if (parent == null) yield break;
foreach (Control child in parent.Controls)
{
TextBox tb = child as TextBox;
if (tb != null)
yield return tb; // found one!
else
foreach(TextBox tb in FindTextBoxes(child))
yield return tb; // found it deeper
}
}
and call it like:
foreach(TextBox tb in FindTextBoxes(lbProducts)
{
if (tb.Name == "txtQuantity")
{
// found a quantity
}
else if (tb.Name == "txtSalePrice")
{
// found the salesprice
}
}

How can I set a table row color in my repeater based on the values databound to that row in ASP.NET?

I have a repeater control:
<table style="width: 100%">
<asp:Repeater runat="server" ID="rptOptions" OnItemDataBound="rptOptions_ItemDataBound">
<HeaderTemplate>
<tr>
<td class="GridHeader">Account</td>
<td class="GridHeader">Margin</td>
<td class="GridHeader">Symbol</td>
<td class="GridHeader">Price</td>
</tr>
</HeaderTemplate>
<ItemTemplate>
<tr>
<td class="GridRow"><asp:Label runat="server" ID="lblOptionAccount"></asp:Label></td>
<td class="GridRow"><asp:Label runat="server" ID="lblOptionMargin"></asp:Label></td>
<td class="GridRow"><asp:Label runat="server" ID="lblOptionSymbol"></asp:Label></td>
<td class="GridRow"><asp:Label runat="server" ID="lblOptionPrice"></asp:Label></td>
</tr>
</ItemTemplate>
</asp:Repeater>
</table>
And the following code-behind databound method:
protected void rptOptions_ItemDataBound(object sender, RepeaterItemEventArgs e)
{
if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
{
Option rowOption = (Option)e.Item.DataItem;
((Label)e.Item.FindControl("lblOptionAccount")).Text = rowOption.Account;
((Label)e.Item.FindControl("lblOptionMargin")).Text = rowOption.Margin ? "Y" : "N";
((Label)e.Item.FindControl("lblOptionSymbol")).Text = rowOption.Symbol;
((Label)e.Item.FindControl("lblOptionPrice")).Text = rowOption.Price.ToString("C", currencyFormat);
}
}
There are more columns in that grid, but I've slimmed it down just for the question.
Now, what I would like to do is change the tr's background color based on the price amount. If it is within different levels, I would like to change the rows background color correspondingly.
Do I have to do this with javascript or is there some way I can get access to the table rows in the code-behind to set this color?

make it to runat="Server"
<tr runat="server" ID="trHeader"></tr>
Then find that Table Row in by ID in your code behind in databound event, like what you are doing for other server side control and change color.

another option:
<tr class="<%# GetClassForPrice( Container.DataItem ) %>">
and in code-behind
protected string GetClassForPrice( object data )
{
var rowOption = (Option)data;
if(rowOption.Price > 100) return "red";
else return "green";
}
also... any reason you're not using data binding? it would let you eliminate your ItemDataBound code-behind method.
<tr>
<td class="GridRow"><%# Eval("Account") %></td>
<td class="GridRow"><%# ((bool)Eval("Margin")) ? "Y" : "N" %></td>
<td class="GridRow"><%# Eval("Symbol") %></td>
<td class="GridRow"><%# Eval("Price", "{0:c}") %></td>
</tr>

use this code inside repeter databound event.
HtmlTableRow tr = (HtmlTableRow)e.Item.FindControl("trID");
tr.Visible = false;

Another option you can use is jQuery. Seeing you're using a repeater, that gives you full control over your output. Jquery can get into your table, look at the data and format it how you want it.
Look at:
http://plugins.jquery.com/project/Plugins/category/54
http://plugins.jquery.com/project/Colorize
http://franca.exofire.net/js/demo_cross.html
Alternately you can use the Code behind in the repeater to set the CSS Class of the cells/rows/columns you need changed.
You'll need to make those controls server controls (require: ID="my_thing" runat="server"), create those controls (use the find control and bind them), then set the CSS class after you determine the value.

Dave Thieben's answer works nicely, except that the css is missing.
If you add the following then the example will work:
table tr.red td { background-color:red; }
table tr.green td { background-color:green; }