function onGridClick(event) {
    var selectedIndex = grid.focus.rowIndex;
    var selectedItem = grid.getItem(selectedIndex);
    selectedId = grid.store.getValue(selectedItem, 'id');
}

<button id="btnDel" dojotype="dijit.form.Button" onclick="DeleteDoc(selectedId)">
                Удалить</button>

function DeleteDoc(selectedId)
{
    alert(selectedId.toString());

    $.ajax({
      type: "POST",
      url: '../Index/DeleteDoc',
      data: { 'selectedId' : selectedId},
    success: function (msg) {
       alert(msg);

    },
    error: function (request, status, error) {
            alert('Ошибка запроса к серверу');
            return false;
      }
    });
}

[HttpPost]
public ActionResult DeleteDoc(int selectedId)
{
    DOCS currentDoc = database.DOCS.First(x => x.ID == selectedId);
    database.DOCS.DeleteObject(currentDoc);
    database.SaveChanges();
    string msg = "Complete!";
    return Json(msg);
}