Using dropdownlist selection I want to update my web grid

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C#

HTML5

MVC4

Using dropdown list selection(Application Name) I am updating my web grid here the problem is while returning from controller like this
return PartialView("_CreateRoles", objPermList);
My dropdown list also getting updated automatically but I don't want this how can I achieve this can you give me any sample example
COntroller
[MustBeLoggedIn, Filters.Compress]
public ActionResult GetPermissionByAppName(string Appname)
{
//some coding
return PartialView("_CreateRoles", objPermList);
}
VIEW

<select id="AppList" onchange="AJAXCall_Fun_LinkRole(GetSelected())">
@foreach (var AppName in Model.ApplicationList)
{
<option id="hid_AppId">@AppName.AppName</option>
}
</select>
<div id="gridcal" style="padding: 20px;">

WebGrid grid = new WebGrid(Model.Permission, rowsPerPage: 20, selectionFieldName: "selectedRow", ajaxUpdateContainerId: "gridcal");
                     grid.Pager(WebGridPagerModes.NextPrevious);}
                @grid.GetHtml(
                tableStyle: "webgrid-table",
                headerStyle: "webgrid-header",
                footerStyle: "webgrid-footer",
                alternatingRowStyle: "webgrid-alternating-row",
                selectedRowStyle: "webgrid-selected-row",
                rowStyle: "webgrid-row-style",
               columns:
            grid.Columns(
            grid.Column("PermName","Permision Name",style: "colWidth"),
            grid.Column(format: @<text><input type="image"  onclick="AJAXCall_Fun_LinkPermission('@item.PermName    ');" src="~/Images/icon-plus.png" name="image" width="9" height="9" /></text>)
              ))