Ignore blank ASP.Net GridView rows while Sorting using C#

I have ASP.Net GridView with 5 TextBoxes in every row. Page size of GridView is 20 records on each page.

I have enabled sorting on every column. When GridView is getting populated, then we are getting 28 filled records and 12 empty records.

When I hit sorting in asc mode on any column, it gives blank rows earlier then records are coming. I wanted to ignore those blank records while sorting.

I tried using custom onsorting method on GridView but it’s not working.

<asp:GridView runat="server" ID="gvDetails" AllowPaging="true" PageSize="20" Allow AutoGenerateColumns="false" 
    DataKeyNames="ProdId" OnPageIndexChanging="gvDetails_PageIndexChanging" OnSorting="gvDetails_OnSorting">
    <HeaderStyle CssClass="headerstyle" />
    <Columns>
        <asp:TemplateField SortExpression="ProdName">
            <ItemTemplate>
                <asp:TextBox ID="txtProductName" runat="server" Text='<%# Eval("ProdName") %>' />
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField SortExpression="ProdDesc">
            <ItemTemplate>
                <asp:TextBox ID="txtProdDesc" runat="server" Text='<%# Eval("ProdDesc") %>' />
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField SortExpression="ProdPrice">
            <ItemTemplate>
                <asp:TextBox ID="txtProdPrice" runat="server" Text='<%# Eval("ProdPrice") %>' />
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField SortExpression="ProdCat">
            <ItemTemplate>
                <asp:TextBox ID="txtProdCat" runat="server" Text='<%# Eval("ProdCat") %>' />
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        BindGridview();
    }
}

protected DataTable BindGridview()
{
    DataSet ds = new DataSet();
    using (SqlConnection con = new SqlConnection("#"))
    {
        con.Open();
        SqlCommand cmd = new SqlCommand("crudoperations", con);
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.Parameters.AddWithValue("@status", "SELECT");
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        da.Fill(ds);
        con.Close();
        if (ds.Tables[0].Rows.Count > 0)
        {
            gvDetails.DataSource = ds;
            gvDetails.DataBind();
        }
        else
        {
            ds.Tables[0].Rows.Add(ds.Tables[0].NewRow());
            gvDetails.DataSource = ds;
            gvDetails.DataBind();
            int columncount = gvDetails.Rows[0].Cells.Count;
            gvDetails.Rows[0].Cells.Clear();
            gvDetails.Rows[0].Cells.Add(new TableCell());
            gvDetails.Rows[0].Cells[0].ColumnSpan = columncount;
            gvDetails.Rows[0].Cells[0].Text = "No Records Found";
        }
    }
    return ds.Tables[0];
}

public void gvDetails_OnSorting(Object sender, GridViewSortEventArgs e)
{
    string sortingDirection = string.Empty;
    if (direction == SortDirection.Ascending)
    {
        direction = SortDirection.Descending;
        sortingDirection = "Desc";

    }
    else
    {
        direction = SortDirection.Ascending;
        sortingDirection = "Asc";

    }
    DataView sortedView = new DataView(BindGridView());
    sortedView.Sort = e.SortExpression + " " + sortingDirection;
    gvDetails.DataSource = sortedView;
    gvDetails.DataBind();
}