check/uncheckbox in gridview tracking - asp.net

Question

i have a below gridview control with a checkbox on it, so my question is when i hit on save button i able to find the checkbox which have been checked and till here no problem, but the problem started when the user tries to uncheck the checkedbox so how would i track the changes and save it into the db that has been checked. anyhelp?
List<Employee> result = new List<Employee>();
long Id = (long)Session["Id"];
result = Employee.GetEmployeeById(Id);
foreach (GridViewRow row in gv.Rows)
{
CheckBox chkBox = row.FindControl("chkSelected") as CheckBox;
if (c != null)
{
if (result.Count > 0)
{
foreach (Employee item in result)
{
Label Id = row.FindControl("lblId") as Label;
if (Id.Text == item.Id.ToString())
{
chkBox.Checked = true;
}
else
{
chkBox.Checked = false;
}
}
}
<asp:TemplateField HeaderText="Select">
<ItemTemplate>
<asp:CheckBox ID="chkSelected" runat="server" Checked="false"></asp:CheckBox>
</ItemTemplate>
</asp:TemplateField>

Answer 1

<script language="javascript" type="text/javascript">
function SelectAll(cb)
{
var gvVar = document.getElementById("<%= gv.ClientID %>");
var cell;
if (gvVar.rows.length > 0)
{
for (i=1; i<gvVar.rows.length; i++)
{
cell = gvVar.rows[i].cells[0];
for (j=0; j<cell.childNodes.length; j++)
{
if (cell.childNodes[j].type =="checkbox")
{
cell.childNodes[j].checked = document.getElementById(cb).checked;
}
}
}
}
}
//--------------------------------------------------------------------------------------------.
function Select(cb)
{
var total = parseInt('<%= this.gv.Rows.Count %>');
var counter=0;
var cbSelectAll=document.getElementById(cb);
var gvVar = document.getElementById("<%= gv.ClientID %>");
var cell;
if (gvVar.rows.length > 0)
{
for (i=1; i<gvVar.rows.length; i++)
{
cell = gvVar.rows[i].cells[0];
for (j=0; j<cell.childNodes.length; j++)
{
if (cell.childNodes[j].type =="checkbox")
{
if(cell.childNodes[j].checked)
counter++;
else
counter--;
}
}
}
}
if(counter==total)
cbSelectAll.checked=true;
else if(counter<total)
cbSelectAll.checked=false;
}
</script>
//----------------------------------------------------------------------------------------
protected void gv_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow && (e.Row.RowState == DataControlRowState.Normal || e.Row.RowState == DataControlRowState.Alternate))
{
CheckBox cbSelect = (CheckBox)e.Row.Cells[0].FindControl("cbSelect");
CheckBox cbSelectAll = (CheckBox)this.gv.HeaderRow.FindControl("cbSelectAll");
cbSelect.Attributes.Add("onclick", "javascript:Select('" + cbSelectAll.ClientID + "')");
cbSelectAll.Attributes.Add("onclick", "javascript:SelectAll('" + cbSelectAll.ClientID + "')");
}
}

Answer 2

Yes, store the original value in a hidden field. If always starting with false, you could use JavaScript to set the hidden value to true when the user clicked the checkbox. Using JQuery, you could do:
<asp:TemplateField HeaderText="Select" ItemStyle-CssClass="Checked">
<ItemTemplate>
<asp:CheckBox ID="chkSelected" runat="server" Checked="false"></asp:CheckBox>
<asp:HiddenField iD="dh" runat="server" />
</ItemTemplate>
</asp:TemplateField>
$("#<%= Grid.ClientID %>").find(".Checked > :checkbox").each(function() {
$(this).siblings("input[type='hidden']").attr("value", "True");
});
Something like that. On Server side, parse the value and if true, then you know it changed.
HTH.

Answer 3

It may not be the brightest idea, but you can query the database for the current state, and the compare with what you have got from the web page during a postback button click, or something like that. Or you can go with Brians answer.
It is possible to persist a list of objects into the Viewstate and access it in a consequent postback. The only thing is that the object you are trying to persist must be defined as serializable.
Update:
The ViewState approach
I feel this may be suitable for your need, and it requires a bit of linq. You'd need to create a class as follows:
[Serializable()]
public class OptionState
{
//the id of the item
int ID {get;set;}
//state of the checkbox
bool Checked {get;set;}
}
Note the Serializable attribute. This is required for the instance to persist to the viewstate.
Add the list of options to the viewstate:
var lstOptions = (from x in <your_option_store>
select new OptionState{ID = x.ID, Checked = x.Checked}).ToList();
ViewState.Add("options", lstOptions);
Here is a bit of code that should go into your button click:
foreach(GridViewRow row in gvOptions.Rows)
{
//not writing the bit of code
//which gets the ID and the
//state of checkbox of
//the gridview row being processed
OptionState currentState = GetOptionStateObjectFromRow(row);
List<OptionState> lstStates = (List<OptionState>) ViewState["options"];
OptionState originalState = lstStates.FirstOrDefault(x => x.ID == currentState.ID);
if(currentState.Checked != originalState.Checked)
{
//the appropriate db call needs to be done here.
}
}