Align GridView Center of Page using Bootstrap and CSS in ASP.Net

Hi anjali600,

Refer below code.

HTML

<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@4.5.3/dist/css/bootstrap.min.css"
    integrity="sha384-TX8t27EcRE3e/ihU7zmQxVncDAy5uIKz4rEkgIXeMed4M0jlfIDPvg6uqKI2xXr2" crossorigin="anonymous" />
<script type="text/javascript" src="https://code.jquery.com/jquery-3.5.1.slim.min.js"
    integrity="sha384-DfXdz2htPH0lsSSs5nCTpuj/zy4C+OGpamoFVy38MVBnE+IbbVYUew+OrCXaRkfj" crossorigin="anonymous"></script>
<script type="text/javascript" src="https://cdn.jsdelivr.net/npm/popper.js@1.16.1/dist/umd/popper.min.js"
    integrity="sha384-9/reFTGAW83EW2RDu2S0VKaIzap3H66lZH81PoYlFhbGU+6BZp6G7niu735Sk7lN" crossorigin="anonymous"></script>
<script type="text/javascript" src="https://cdn.jsdelivr.net/npm/bootstrap@4.5.3/dist/js/bootstrap.min.js"
    integrity="sha384-w1Q4orYjBQndcko6MimVbzY0tgp4pWB4lZ7lr30WKz0vr/aWKhXdBNmNb5D92v7s" crossorigin="anonymous"></script>
<table class="table table-sm">
    <tr>
        <td align="center">
            <asp:GridView ID="grdTest" runat="server" GridLines="Horizontal" Width="25%" Style="min-width: 160px"
                CssClass="table table-sm table-bordered table-condensed table-responsive-sm table-hover table-striped">
            </asp:GridView>
        </td>
    </tr>
</table>

Code

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        DataTable dt = new DataTable();
        dt.Columns.AddRange(new DataColumn[] { new DataColumn("Calculation"), new DataColumn("Value") });
        dt.Rows.Add("Test 1", 1235);
        dt.Rows.Add("Test 2", 66666);
        dt.Rows.Add("Test 3", 9999);
        dt.Rows.Add("Test 4", 666555);
        grdTest.DataSource = dt;
        grdTest.DataBind();
    }
}