I had got solution after a day war.Here it goes.I got solution from nokia developer site. you can get whether checkbox inside datatemplate is checked and its corresponding Textblock value.
//Variables to store the count of checked Checkboxes and their data
public string option_selected = "";
public int check_count = 0;
//SearchElement populates above variables for checkboxes in specified "targeted_control"
public void SearchElement(DependencyObject targeted_control)
{
var count = VisualTreeHelper.GetChildrenCount(targeted_control); // targeted_control is the listbox
if (count > 0)
{
for (int i = 0; i < count; i++)
{
var child = VisualTreeHelper.GetChild(targeted_control, i);
if (child is CheckBox) // specific/child control
{
CheckBox targeted_element = (CheckBox)child;
if (targeted_element.IsChecked == true)
{
if (targeted_element.Tag!= null)
{
// get the value associated with the "checked" checkbox
option_selected = targeted_element.Tag.ToString();
}
// count the number of "Checked" checkboxes
//check_count = check_count + 1;
return;
}
}
else
{
SearchElement(child);
}
}
}
else
{
return;
}
}