A field or property with the name 'bname' was not found on the selected data source

Question

I know this type of question has been asked multiple times, with solved answers. I've tried them all, but none of it seems to work. Please have a look and maybe help me in understanding where I am going wrong.

.aspx

      <asp:view ID="view2" runat="server">
            <asp:GridView ID="gvBatches" runat="server" AutoGenerateColumns="False" CssClass="table-hover table" GridLines="None" Width="900px" ShowFooter="True" >
            <columns>
               <asp:BoundField  DataField="bname" HeaderText="Batch Name" />
            </columns>  
            </asp:GridView>
  </asp:view>

.aspx.cs

        protected void Page_Load(object sender, EventArgs e)
         {

            if (!Page.IsPostBack)
            {
                if (ViewState["query"] == null)
                {
                    ViewState["query"] = "select course from tblCourses";
                }
                if (MultiView1.ActiveViewIndex == '1')
                {
                    bindgrid1();
                }

                bindgrid();
            }
        }

    protected void bindgrid1()
    {
        SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["DBCS"].ConnectionString);
        DataTable dt1 = new DataTable();
        using (SqlDataAdapter sda = new SqlDataAdapter(ViewState["query"].ToString(), con))
        {
            sda.Fill(dt1);
        }
        gvBatches.DataSource = dt1;
        gvBatches.DataBind();
    }
if (e.CommandName == "viewbat")
        {
            ViewState["query"] = "select bname from tblBatches where course='" + e.CommandArgument.ToString() + "'";
            MultiView1.ActiveViewIndex = 1;
        }

Multiview index is changed when a LinkButton(commandName="viewbat") is clicked on a different GridView(gvCourses with datafield="course" and that works fine).

The code throws same error even if the query is changed to simple:

select * from tblBatches

Database design:

Database design is as shown, consists 'bname'