How to get two input values to two parameters in MVC View Button OnClick method?

You can implement your requirement by jQuery like this

Update cshtml

<input type="text" id="txtRemarks" value="Test" />
<input type="text" id="txtCost" value="10" />
<input type="button" id="btnAddtoGrid" value="Add" class="btn btn-group" />
<input type="button" id="btnAddtoGrid" value="Add" class="btn btn-group" />
<input type="button" id="btnAddtoGrid" value="Add" class="btn btn-group" />
<input type="button" id="btnAddtoGrid" value="Add" class="btn btn-group" />
<input type="button" id="btnAddtoGrid" value="Add" class="btn btn-group" />
<input type="button" id="btnAddtoGrid" value="Add" class="btn btn-group" />

Add script tag to cshtml

<script src="~/Scripts/jquery-1.10.2.min.js"></script>
<script>
    $(document).ready(function() {
       updateAttr();
    });
    $("#txtRemarks, #txtCost").change(function() {
        updateAttr();
    });

    function updateAttr() {
        $('input[type="button"]').each(function(index, item) {

            var onclick = 'location.href=';
            onclick += '@Url.Action("ServiceDetails", "ServiceHeaders")';

            onclick += "?Remark=" + $('#txtRemarks').val();
            onclick += "?Cost=" + $('#txtCost').val();
            $(item).attr('onclick', onclick);
        });
    }

</script>

I tested and it worked

I would rely on the standard ASP.NET MVC helpers:

chtml

@using (Html.BeginForm("AddServiceHeaders", "ServiceDetails", FormMethod.Post))  
{ 
    @Html.EditorFor(model => model.Remark)  
    @Html.EditorFor(model => model.Cost)  

    <input type="button" id="btnAddtoGrid" value="Add" class="btn btn-group" />
}

c#

public sealed class Model {
    public string Remark { get; set; }
    public int Cost { get; set; }
}

public class ServiceDetailsController : Controller {

    [HttpPost]
    public ActionResult AddServiceHeaders(Model model){
        // ..
    }

}

See example: Music Store.

I would recommend to:

• use POST-verb for any data update (pass params to the server in the request body, not the query string)
• use input-validation
• protect your data from malicious actions - see AntiForgeryToken