jqgrid MVC omit some columns from ModelState - asp.net-mvc

Question

I have a jqGrid in MVC setup as:
<script type="text/javascript">
jQuery(document).ready(function () {
jQuery("#list").jqGrid({
url: '/Home/DynamicGridData/',
datatype: 'json',
mtype: 'POST',
colNames: ['id', 'note', 'tax', 'PaymentType', 'CreatedByUsername', 'Actions'],
colModel: [
{ name: 'id', index: 'id', hidden: true, key: true, editable: true, editrules:{ required:false } },
{ name: 'note', index: 'note', width: 40,align:'center', editable: true, editrules: { required : true } },
{ name: 'tax', index: 'tax', width: 400, align: 'center', editable: true, editrules: { required : true } },
{ name: 'PaymentTypeId', index: 'PaymentTypeId', width: 400, align: 'center', editable: true, edittype:"select",
editoptions: { dataUrl: '/Home/PaymentTypes/' }},
{ name: 'CreatedByUsername', index: 'CreatedByUsername', hidden: true, editable: true, editrules:{ required:false } },
{ name: 'act',index:'act',width:55,align:'center',sortable:false,formatter:'actions',
formatoptions:{
keys: true, // we want use [Enter] key to save the row and [Esc] to cancel editing.
beforeSubmit:function(postdata, formid) {
alert("Hi");
jQuery("#ValidationSummary").show('slow');
},
},}
],
pager: jQuery('#pager'),
rowNum: 10,
rowList: [5, 10, 20, 50],
sortname: 'Id',
sortorder: "desc",
viewrecords: true,
imgpath: '',
caption: 'My first grid',
editurl: '/Home/Save/'
});
jQuery("#list").navGrid('#pager', { edit: false, search: false, add: true });
});
</script>
When creating on submit it goes to the save method on the controller.
As you can see CreatedByUsername and id are hidden for normal view and edit.
When I add new data though I find that ModelState.IsValid = false.
I've managed to make it so that CreatedByUsername does not added an error to the ModelState even though no data is added for it on insert through editrules:{ required:false }.
The problem is this same piece of code doesn't work for the id and is adding an Error to the ModelState of "The id field is required."
Can anyone please tell me how to prevent this from happening for the id field?

Answer 1

The problem is that your id field has the key attribute and besides your validation rule this field is required. A workaround is to define a custom function for validation an always return true

Answer 2

Can you set the id field in your viewmodel to nullable? Like this:
public int? Id { get; set; }
If the id is not nullable, mvc will automatically create a validation error. If you're not using a viewmodel, but just using parameters on your save action, you can set the id parameter to nullable.