Finding in which row a Button was clicked in a GridView/Repeater - asp.net

Question

I am binding a Repeater. Each row (is that the right word?) in the Repeater has a Button and a HiddenField. How do I determine the Value of the HiddenField based on which Button was clicked?
Code behind for Button's OnClick event:
protected void btnButton1_Click(object sender, EventArgs e)
{
Button btnButton1 = (Button)sender;
// how do i get this row's HiddenField Value?
}
edit: the CommandArgument suggestion from Pleun works but I am still having issues. I need to find the row(?) in the Repeater that the Button belongs to as there is also a TextBox in each row and I would need its value. So ideally I want to get that row and go FindControl("TextBox1") etc etc. Sorry, should have stated that in my initial question

Answer 1

What I like to do is add a CommandArgument to the button. In this code its an imagebutton but the idea is the same. So also no need for an extra hidden field.
<asp:ImageButton ID="btnMail" ImageUrl="~/imgnew/prof/sendlink.png"
CommandArgument='<%# Eval("id")%>'
And in the _Click event do
string id = ((ImageButton)sender).CommandArgument;
Update:
If you need all the data, you need a different event. The data in the repeater is available as Item in
RepeaterCommandEventArgs
in the Command event (RepeaterCommandEventArgs)
for handling the Command event see this example
http://www.asp.net/data-access/tutorials/custom-buttons-in-the-datalist-and-repeater-cs
or
http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.repeatercommandeventargs.aspx

Answer 2

If you using Repeater you can identify elements in each row in the ItemDataBound.
If you using gridview use RowDataBound
Hope this helps

Answer 3

You can traverse upwards by getting the button's Parent, then doing a FindControl() on that control.
Row parentRow = (Row)((Button)sender).Parent;
var tBox = (System.Web.UI.WebControls.TextBox)parentRow.FindControl("myTextBox")
You may have to play around to see how deep the button is nested and with what control types to get to the appropriate parent.

Answer 4

My markup code:
<asp:Repeater ID="RptFiles" runat="server">
<HeaderTemplate>
<table>
</HeaderTemplate>
<ItemTemplate>
<tr>
<td>--</td>
<td><%#Eval("title")%></td>
<td>
<asp:FileUpload ID="fuVersion" runat="server" />
<asp:Button ID="btnUploadVersion" Text="Last opp" runat="server" OnClick="btnUploadVersion_Click" CommandArgument='<%#Eval("Id") %>' />
</td>
</tr>
</ItemTemplate>
<FooterTemplate>
</table>
</FooterTemplate>
</asp:Repeater>
My code behind
protected void Upload_Click(object sender, EventArgs e)
{
Button btn = (Button)sender;
var documentId = btn.CommandArgument;
//Get the Repeater Item reference
RepeaterItem item = btn.NamingContainer as RepeaterItem;
var fuVersion = (FileUpload)item.FindControl("fuVersion");
var filename = fuVersion.PostedFile.FileName
}