dataAdapter = new SqlDataAdapter("SELECT *  FROM Turs", sqlcn);
    dt = new DataTable("Turs");
    dataAdapter.Fill(dt);
    GridView1.DataSource = dt;
    GridView1.DataBind();

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
        {
            e.Row.Cells[0].Width = 100;
            e.Row.Cells[1].Width = 150;
        }

<asp:GridView ID="GridView1" runat="server" AllowPaging="True" AllowSorting="True"
            BorderColor="Black" BorderStyle="Solid" BorderWidth="1px" Font-Size="Medium"
            ShowHeaderWhenEmpty="True" AutoGenerateColumns="True" 
            onrowdatabound="GridView1_RowDataBound">
            <EditRowStyle BorderColor="Black" BorderStyle="Solid" BorderWidth="1px" />
            <HeaderStyle Font-Bold="True" Font-Size="Larger" ForeColor="Blue" />
            <RowStyle BorderColor="Black" BorderStyle="Solid" BorderWidth="1px" />
        </asp:GridView>