How to compare viewbag value with model another value in mvc 4 - asp.net-mvc

Question

I am trying to send viewbag from action method to view. When first page loads viewbag value will be null. when I call CheckPermissions action method viewbag gets some value and it will return the same view that time viewbag contains some value and now I want to compare viewbag value with another value. I tried but following error appearing. Cannot perform runtime binding on a null reference.
This is my Index view code.
#model c3card.Models.GroupPermissionVM
#{
ViewBag.Title = "Index";
}
#using (Html.BeginForm())
{
#Html.LabelFor(m=>m.GroupID)
#Html.DropDownListFor(m => m.GroupID, Model.GroupList, "Please select", new { id = "ddlgrp" })
foreach(var permission in Model.Permissions)
{
if (ViewBag.marlid.equals(permission))
{
<label>
#Html.RadioButtonFor(m => m.perm_id, permission.perm_id, new {#checked="true"})
<span>#permission.perm_levelname</span>
</label>
}
else
{
<label>
#Html.RadioButtonFor(m => m.perm_id, permission.perm_id)
<span>#permission.perm_levelname</span>
</label>
}
}
This is my action method
public ActionResult CheckPermissions(int id)
{
var groups = db.tm_grp_group.Where(a => a.grp_isactive == true);
var permissions = db.tm_perm_level;
GroupPermissionVM model = new GroupPermissionVM
{
marlid=db.ts_grp_perm_mapping.Select(p=>p.grp_id==id).Count(),
GroupList = new SelectList(groups, "grp_id", "grp_name"),
Permissions = permissions.Select(p => new PermissionVM
{
perm_id = p.perm_id,
perm_levelname = p.perm_levelname
})
};
ViewBag.marlid = db.ts_grp_perm_mapping.Select(p => p.grp_id == id).Count();
return View("Index",model);
}
Any suggestion why I am not able to compare values inside if condition? Thanks in advance. This line causing me error if (ViewBag.marlid.equals(permission))
I edited as follows
foreach(var permission in Model.Permissions)
{
if(Model.marlid==permission.perm_id)
{
<label>
#Html.RadioButtonFor(m => m.perm_id, permission.perm_id,new { #checked = true } )#Model.marlid.ToString()
<span>#permission.perm_levelname</span>
</label>
}

Answer 1

You can change the code given below
if(ViewBag.marlid != null && Model.Permissions != null)
{
foreach(var permission in Model.Permissions)
{
if(ViewBag.marlid == permission.perm_id)
{
<label>
#Html.RadioButtonFor(m => m.perm_id, permission.perm_id,new { #checked = true } )#Model.marlid.ToString()
<span>#permission.perm_levelname</span>
</label>
}
}
}
Hope this helps.