Batch deletion after the GridView is selected in ASP.net

<form id= "Form1" runat= "Server" >
<asp:button id= "Delall" runat= "server" text= "Delete selected" onclick= "Delall_click"
<div>
<asp:gridview id= "Gvuser" runat= "Server"
autogeneratecolumns= "False" datakeynames= "UserId"
Datasourceid= "Objectdatasourceuser" onrowdeleted= "gvuser_rowdeleted"
Cellpadding= "4" forecolor= "#333333" gridlines= "None" allowpaging= "True"
Pagesize= "3" >
<alternatingrowstyle backcolor= "White" forecolor= "#284775"/>

<Columns>
<asp:TemplateField>
<HeaderTemplate>
<input id= "Checkall" type= checkbox "onclick=" SelectAll (this); "/> Select All
</HeaderTemplate>
<ItemTemplate>
<asp:checkbox runat= "Server" id= "Checksingle"/>
</ItemTemplate>
<itemstyle width= "100px"/>

</asp:TemplateField><asp:boundfield datafield= "UserId" headertext= "UserId"
sortexpression= "UserId"/>
<asp:boundfield datafield= "UserName" headertext= "UserName"
sortexpression= "UserName"/>
<asp:boundfield datafield= "Userpass" headertext= "Userpass"
sortexpression= "Userpass"/>
<asp:boundfield datafield= "role" headertext= "role" sortexpression= "role"/>
<asp:boundfield datafield= "Regtime" headertext= "Regtime"
sortexpression= "Regtime"/>
<asp:boundfield datafield= "Lognum" headertext= "Lognum"
sortexpression= "Lognum"/>
<%--<asp:commandfield showeditbutton= "True"/>--%>
<asp:TemplateField>
<EditItemTemplate>
<asp:linkbutton id= "LinkButton4" runat= "Server" commandname= "Update" > Update </asp:LinkButton>
<asp:linkbutton id= "LinkButton5" runat= "Server" commandname= "Cancel" > Cancel </asp:LinkButton>
</EditItemTemplate>
<ItemTemplate>
<asp:linkbutton id= "LinkButton3" runat= "Server" commandname= "edit" > Edit </asp:LinkButton>
</ItemTemplate>
</asp:TemplateField>
<asp:templatefield headertext= "Action" showheader= "False" >
<ItemTemplate>
<asp:linkbutton id= "Lbdelete" runat= "Server" causesvalidation= "False"
onclientclick= "return confirm (' Are you sure you want to delete it? ')" text= "Delete" commandname= "delete" ></asp:LinkButton>
</ItemTemplate>
<itemstyle horizontalalign= "Center" verticalalign= "Middle"/>
</asp:TemplateField>
</Columns>
<editrowstyle backcolor= "#999999"/>
<footerstyle backcolor= "#5D7B9D" font-bold= "True" forecolor= "white"/>
<pagerstyle backcolor= "#284775" forecolor= "white" horizontalalign= "Center"/>
<rowstyle backcolor= "#F7F6F3" forecolor= "#333333"/>
<selectedrowstyle backcolor= "#E2DED6" font-bold= "True" forecolor= "#333333"/>
<sortedascendingcellstyle backcolor= "#E9E7E2"/>
<sortedascendingheaderstyle backcolor= "#506C8C"/>
<sorteddescendingcellstyle backcolor= "#FFFDF8"/>
<sorteddescendingheaderstyle backcolor= "#6F8DAE"/>
</asp:GridView>
<asp:objectdatasource id= "Objectdatasourceuser" runat= "Server"
Dataobjecttypename= "User" deletemethod= "DeleteUser" insertmethod= "AddUser"
Selectmethod= "GetAllUsers" typename= "UserService" updatemethod= "ModifyUser" >
</asp:ObjectDataSource>
</div>
</form>
<script type= "Text/javascript" >
function SelectAll (obj) {
var chkall = obj;
state = chkall.checked;
Elem = chkall.form.elements;
for (i = 0; i < elem.length; i++) {
if (Elem[i].type = = "checkbox" && Elem[i]!= chkall.id) {
if (elem[i].checked!= state) {
Elem[i].click ();
}
}
}
}

</script>

protected void Delall_click (object sender, EventArgs e)
{
Int intcount = This.gvUser.Rows.Count;
for (int i = 0; i < intcount; i++)
{
CheckBox checksingle = this.gvuser.rows[i]. Cells[0]. FindControl ("Checksingle") as CheckBox;
if (checksingle.checked)
{
Userservice.deleteuserbyuserid (Convert.ToInt16 (this.gvuser.datakeys[i). Values[0]));
}
}
Post-delete Updates
Gvuser.databind ();
}