function select_deselectAll (chkVal, idVal)
{
   var frm = document.forms[0];
    // Loop through all elements
   for (i=0;i< frm.length; i++)
   {
     // Look for our Header Template's Checkbox
       if (idVal.indexOf ('CheckAll') != -1)
       {
         // Check if main checkbox is checked, then select or deselect datagrid checkboxes
	if(chkVal == true)
	{
	  frm.elements[i].checked = true;
	}
	else
	{
	frm.elements[i].checked = false;
	}
	// Work here with the Item Template's multiple checkboxes
         }
       else if (idVal.indexOf ('DeleteThis') != -1)
       {
    	 // Check if any of the checkboxes are not checked, and then uncheck top select all checkbox
	 if (frm.elements[i].checked == false)
	 {
	   frm.elements[1].checked = false; 
	   //Uncheck main select all checkbox
	 }
        }
  }
}
function confirmDelete (frm)
{
  // loop through all elements
  for (i=0; i<frm.length; i++)
  {
    // Look for our checkboxes only
   if (frm.elements[i].name.indexOf("DeleteThis") !=-1)
    {
      // If any are checked then confirm alert, otherwise nothing happens
      if(frm.elements[i].checked)
      {
       return confirm ('Are you sure you want to delete your selection(s)?')
      }
    }
 }
}


<ASP:DataGrid id="MyDataGrid" runat="server" Width="700" BackColor="white" BorderColor="black"
CellPadding="3" CellSpacing="0" Font-Size="9pt" AutoGenerateColumns="False" HeaderStyle-BackColor="darkred" HeaderStyle-ForeColor="white">
< Columns>
< asp:TemplateColumn>
< HeaderTemplate>
< asp:CheckBox ID="CheckAll" OnCheckedChanged="javascript: return select_deselectAll (this.checked,this.id);" runat="server" />
< font face="Webdings" color="white" size="4">< /font>
< /HeaderTemplate>
< ItemTemplate>
< asp:CheckBox ID="DeleteThis" OnCheckedChanged="javascript: return select_deselectAll (this.checked, this.id);"	runat="server" />
< /ItemTemplate>
< /asp:TemplateColumn>
< asp:TemplateColumn>
< HeaderTemplate>
ID
< /HeaderTemplate>
< ItemTemplate>
< asp:Label ID="StoreID" Text='< %# DataBinder.Eval (Container.DataItem, "ID") %>' runat="server"/>
< /ItemTemplate>
< /asp:TemplateColumn>
< asp:BoundColumn HeaderText="Store" Datafield="Store" runat="server" />
< asp:BoundColumn HeaderText="Address" Datafield="Address" runat="server" />
< asp:BoundColumn HeaderText="City" Datafield="City" runat="server" />
< asp:BoundColumn HeaderText="State" Datafield="State" runat="server" />
< asp:BoundColumn HeaderText="Zip" Datafield="Zip" runat="server" />
< /Columns>
< /ASP:DataGrid>


< asp:Button Text="Delete Items" OnClick="DeleteStore" ID="Confirm" runat="server" />
< span id="OutputMsg" runat="server" />

public void DeleteStore (Object sender, EventArgs e) 
{
	string dgIDs = "";
	bool BxsChkd = false; 
	foreach (DataGridItem i in MyDataGrid.Items) 
	{
	CheckBox deleteChkBxItem = (CheckBox) i.FindControl ("DeleteThis");
	if (deleteChkBxItem.Checked) 
	{
	BxsChkd = true;
	// Concatenate DataGrid item with comma for SQL Delete
	dgIDs += ((Label) i.FindControl ("StoreID")).Text.ToString() + ",";
	}
}
// Set up SQL Delete statement, using LastIndexOf to remove tail comma from string.
string deleteSQL = "DELETE from Stores WHERE stor_id IN (" + dgIDs.Substring (0, dgIDs.LastIndexOf (",")) + ")";
if (BxsChkd == true) 
{
 // Execute SQL Query only if checkboxes are checked, otherwise error occurs with initial null string
try 
{
SqlHelper.ExecuteNonQuery (objConnect, CommandType.Text, deleteSQL);
} 
catch (SqlException err) 
{ 
//Exception Catching code as usual displaying message
}
//Refresh data
BindData();
}
}
public void BindData() 
{
String sqlQuery = "Select stor_id As Id, stor_name As Store, City, State, Zip from Stores";
MyDataGrid.DataSource = SqlHelper.ExecuteDataset(objConnect, CommandType.Text, sqlQuery);
MyDataGrid.DataBind();
objConnect.Close();
objConnect = null;
}