Rotate ASP.NET GridView: Convert GridView Columns to Rows and Rows to Columns

<asp:GridView ID="GridView1" CssClass="Grid" HeaderStyle-CssClass="header" runat="server" AutoGenerateColumns="true">
</asp:GridView>
<br />
<asp:Button ID="btnConvert1" runat="server" Text="Convert Rows to Columns" OnClick="Convert" CommandArgument="1" />
<asp:Button ID="btnConvert2" runat="server" Text="Convert Columns to Rows" OnClick="Convert" CommandArgument="2" Visible="false" />

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        DataTable dt = new DataTable();
        dt.Columns.AddRange(new DataColumn[3]
        {
            new DataColumn("Item"), new DataColumn("Quantity"), new DataColumn("Price")
        });
        dt.Rows.Add("Shirt", 145, 500);
        dt.Rows.Add("Jeans", 0, 2000);
        dt.Rows.Add("Trousers", 190, 1545);
        dt.Rows.Add("Tie", 30, 200);
        dt.Rows.Add("Cap", 0, 300);
        dt.Rows.Add("Hat", 90, 350);
        dt.Rows.Add("Scarf", 290, 140);
        dt.Rows.Add("Belt", 150, 400);
        ViewState["dt"] = dt;
        BindGrid(dt, false);
    }
}
private void BindGrid(DataTable dt, bool rotate)
{
    GridView1.ShowHeader = !rotate;
    GridView1.DataSource = dt;
    GridView1.DataBind();
    if (rotate)
    {
        foreach(GridViewRow row in GridView1.Rows)
        {
            row.Cells[0].CssClass = "header";
        }
    }
}

protected void Convert(object sender, EventArgs e)
{
    DataTable dt = (DataTable) ViewState["dt"];
    if ((sender as Button).CommandArgument == "1")
    {
        btnConvert1.Visible = false;
        btnConvert2.Visible = true;
        DataTable dt2 = new DataTable();
        for (int i = 0; i <= dt.Rows.Count; i++)
        {
            dt2.Columns.Add();
        }
        for (int i = 0; i < dt.Columns.Count; i++)
        {
            dt2.Rows.Add();
            dt2.Rows[i][0] = dt.Columns[i].ColumnName;
        }
        for (int i = 0; i < dt.Columns.Count; i++)
        {
            for (int j = 0; j < dt.Rows.Count; j++)
            {
                dt2.Rows[i][j + 1] = dt.Rows[j][i];
            }
        }
        BindGrid(dt2, true);
    } else
    {
        btnConvert1.Visible = true;
        btnConvert2.Visible = false;
        BindGrid(dt, false);
    }
}