checkbox checked inside data list c#

Question

i have a form in which  i will bind out off stock product in data list 

 

and inside data list  have check box

 

i want when which item checked then it convert  into  out of stock to available   product

 

this is work properly but when first item checked then it convert   into out of stock to available product but facing error like:

Collection was modified; enumeration operation may not execute.  

 

and my code is like:  on check box checkedchande

 

foreach (DataListItem item in divProducts.Items)

{

Label ProductId = (Label)item.FindControl("label_product");

CheckBox chkbox = (CheckBox)item.FindControl("chkbox");

if (chkbox.Checked)

{

objAdmin.OperationName = "update_avail";

objAdmin.ProductId = Convert.ToInt16(ProductId.Text);

objAdmin.Pro_avail = "Available";

objAdmin.Quantity = 30;

DataSet ds = objAdmin.selectoutofstock();

BindGrid();

}

}