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Error in getting Nullreferenceexception even though there is text assigned to the label

I have been getting the NullrefernceException on my aspx.cs page even though I already assigned a text for the label in my aspx page. At first i thought it could be the session but i log in and try i still get the same error. I have checked my database and the spelling and there is nothing wrong
My aspx.cs code:
protected void Page_Load(object sender, EventArgs e)
{
Label Lefthowmanylabel =(Label)DataList1.FindControl("Lefthowmanylabel");
Label quantitylabel = (Label)DataList1.FindControl("quantitylabel");
if (int.Parse(quantitylabel.Text) < 11)
{
Lefthowmanylabel.Visible = true;
}
else
{
Lefthowmanylabel.Visible = false;
}
}
My datalist item in aspx page:
<asp:Label ID="Lefthowmanylabel" runat="server" Text="Only 10 Left!! While stock last!" Visible="False"/>
<asp:Label ID="quantitylabel" runat="server" Text='<%# Eval("Quantity") %>' Visible="False" />
</td>

If you want to access access controls inside DataList and manipulate them, you want to use ItemDataBound.
For example,
<asp:DataList ... OnItemDataBound="Item_Bound" runat="server">
</asp:DataList>
void Item_Bound(Object sender, DataListItemEventArgs e)
{
if (e.Item.ItemType == ListItemType.Item ||
e.Item.ItemType == ListItemType.AlternatingItem)
{
Label lefthowmanylabel =(Label)e.Item.FindControl("Lefthowmanylabel");
Label quantitylabel = (Label)e.Item.FindControl("quantitylabel");
if (int.Parse(quantitylabel.Text) < 11)
{
lefthowmanylabel.Visible = true;
}
else
{
lefthowmanylabel.Visible = false;
}
}
}

How to make button visible inside repeater?

Here I have kept two button(btnhide and btnunhide) and a label inside the repeater and I have made button btnunhide invisible initially. Now what I want is that as I press button btnhide then btnunhide which is invisible intially should be visible.
Solution Will Be great help.
Html used
<asp:Repeater ID="Repeater1" runat="server" OnItemCommand="Repeater1_ItemCommand" >
<ItemTemplate>
<asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
<asp:Button ID="btn" CommandName="h" runat="server" Text="Hide" />
<asp:Button ID="btnhide" Visible="false" runat="server" Text="Unhide" />
</ItemTemplate>
</asp:Repeater>
Code behind
protected void Repeater1_ItemCommand(object source, RepeaterCommandEventArgs e)
{
if (e.CommandName == "h")
{
}
}

You can achieve this by just a single button by changing the Text to hide/unhide and do the functionality as required by just checking the Text property of the button.
protected void Repeater1_ItemCommand(object source, RepeaterCommandEventArgs e)
{
if (e.CommandName == "h")
{
Button btn = (Button)(e.CommandSource);
if(btn.Text == "hide")
{
btn.Text = "unhide";
//Do additional work here, when unhiding.
}
else
{
btn.Text = "hide";
//Do additional work here, when hiding.
}
}
}
I Hope, this helps. Thanks

How to add web user controls to repeater

Scenario:
UsrControl: custom user control, which contains a textbox and a button, rederend horizontally (in one line).
UsrControlContainer: custom user control, which should be able to display multiple UsrControl objects (each object in seperate line, so the Seperator template will probably be <br />. This control also contains a button, which adds new UsrControl to the collection.
My code:
<asp:Button ID="Button1" runat="server" Text="Button" onclick="Button1_Click"/>
<asp:Repeater ID="rptExample" runat="server">
<ItemTemplate>
</ItemTemplate>
<SeparatorTemplate><br /></SeparatorTemplate>
</asp:Repeater>
And:
protected void Button1_Click(object sender, EventArgs e)
{
rptExample.DataSource = new List<UsrControl> {new UsrControl(), new UsrControl()};
rptExample.DataBind();
}
Simple question - what should I put in ItemTemplate to make this work?
Edit - I also want to pass some parameters to UsrControl before rendering it.

<asp:Repeater ID="rptExample" runat="server">
<ItemTemplate>
<uc:UsrControl runat="server" />
</ItemTemplate>
<SeparatorTemplate><br /></SeparatorTemplate>
</asp:Repeater>
protected void Button1_Click(object sender, EventArgs e)
{
rptExample.DataSource = Enumerable.Range(0, 2);
rptExample.DataBind();
}

Following your question in answer. You can catch every binding object in ItemDataBound event. So for example, as i used, set whole object as user control property.
protected void PersonesRepeater_ItemDataBound(object sender, RepeaterItemEventArgs e)
{
if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
{
PersonLine line = (PersonLine)e.Item.FindControl("Person1");
line.Person = e.Item.DataItem as Osoba;
}
}
Ofcourse, you have to add the event handler to your repeater:
<asp:Repeater runat="server" ID="PersonesRepeater" OnItemDataBound="PersonesRepeater_ItemDataBound"><ItemTemplate>
<my:Person ID="Person1" runat="server" />
</ItemTemplate>
</asp:Repeater>

Problem with a hyperlink

I put a hyperlink inside a datalist..
<ItemTemplate>
<asp:HyperLink ID="HyperLink1" runat="server">'<%# Eval("ThreadTitle") %>'</asp:HyperLink>
<br />
<br />
</ItemTemplate>
I want it to enable it to be pressed so that the datalist event will be triggered and transfer me to another page:
protected void DataList1_SelectedIndexChanged(object sender, EventArgs e)
{
Server.Transfer("AnswerQuestion.aspx?x=" + DataList1.DataKeyField + "&question=" + DataList1.SelectedValue + "&time=" + DateTime.Now);
}
Unfortunately, the link seems to be disabled and I cant press on it to trigger the DataList Selected event..
How can I make the hyperlink active ?

If you want to trigger a selecteditemchaned event use a LinkButton instead of hyperlink.
<asp:DataList ID="DataList1" runat="server"
onselectedindexchanged="DataList1_SelectedIndexChanged">
<ItemTemplate>
<asp:LinkButton ID="sjdj" runat="server" CommandName="Select">
<%# Container.DataItem %></asp:LinkButton>
</ItemTemplate>
</asp:DataList>
In the code behind have
protected void DataList1_SelectedIndexChanged(object sender, EventArgs e)
{
Server.Transfer("~/jjtestjj.aspx?" + DataList1.DataKeyField);
}

why arent you using the Hyperlink as a hyperlink?
You can set the NavigationURL and Text using the OnItemDataBound (or equivalent) event.
this code works with an asp:Repeater:
protected void Row_DataItem(object row, RepeaterItemEventArgs args)
{
if (args.Item.ItemType == ListItemType.AlternatingItem || args.Item.ItemType == ListItemType.Item)
{
var item = (DataItemPOCO)args.Item.DataItem;
var link = (HyperLink)args.Item.FindControl("HyperLink1");
link.Text = item.LinkText;
link.NavigateUrl = item.URL;
}
}

C# Pass textbox content via CommandArgument in Repeater

<asp:Repeater ID="Cartridges" runat="server" onitemcommand="Cartridges_ItemCommand">
<ItemTemplate>
<p class="cartprice"><%#String.Format("{0:C}", Eval("Price"))%></p>
<hr class="hr4" />
<p class="cartqty">QTY <asp:TextBox ID="cartQty" Text="0" runat="server"></asp:TextBox> </p>
<div class="cartbuy2"><asp:LinkButton ID="buy" runat="server" CommandName="AddtoCart" CommandArgument=<%#Eval("cartID") %> Text="Buy"></asp:LinkButton></div>
</ItemTemplate>
</asp:Repeater>
How can I pass the textbox value within CommandArgument? Sorry totally lost...

Did you try: CommandArgument='<%#Eval("cartID") %>'
this is different from yours as it is surrounded by a single quote, I guess this is the correct syntax.

Use FindControl to get other items in the repeater Item. For Example:
protected void repeater_ItemCommand(object sender, RepeaterCommandEventArgs e)
{
LinkButton lb = (LinkButton)e.CommandSource;
string textBoxValue = ((TextBox)lb.Parent.FindControl("cartQty")).Text;
}

you need to bind the cartId to the linkbutton onItemDataBound and then access it onItemCommand, I have modified code for you, give this a go
<asp:Repeater ID="Cartridges" runat="server" onitemcommand="Repeater_OnItemCommand" OnItemDataBound="Repeater_OnItemDataBound">
<ItemTemplate>
<p class="cartprice"><%#String.Format("{0:C}", Eval("Price"))%></p>
<hr class="hr4" />
<p class="cartqty">QTY <asp:TextBox ID="cartQty" Text="0" runat="server"></asp:TextBox> </p>
<div class="cartbuy2"><asp:LinkButton ID="buy" runat="server" CommandName="AddtoCart" Text="Buy"></asp:LinkButton></div>
your onItemdatabound should look like this
protected void Repeater_OnItemDataBound(object sender, RepeaterItemEventArgs e)
{
if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
{
//your code...
LinkButton add = (LinkButton)e.Item.FindControl("buy");
add.CommandArgument = cartID.ToString();
}
and then you can access the text box on item command like this
protected void Repeater_OnItemCommand(object source, RepeaterCommandEventArgs e)
{
if (e.CommandName == "AddtoCart")
{
LinkButton btnEdit = (LinkButton)e.CommandSource;
if (btnEdit != null)
{
string editId = btnEdit.CommandArgument;
string text = ((TextBox)e.Item.FindControl("cartQty")).Text;
//do some stuff with your cartid and quantity
}
}
}
You can also extend your code with edit/delete command arguments by adding more linkbuttons and binding them to the correct command and then accessing them in on item command
Thanks