Insert value in DataTable empty cell in ASP.Net using C#

Hii Amar,

Kindly refer below Sample.

HTML

<table>
    <tr>
        <th>Number:</th>
        <td><asp:TextBox runat="server" ID="txtNUmber" /></td>
    </tr>
    <tr>
        <th colspan="2"><asp:Button Text="Save" ID="btnSave" runat="server" OnClick="OnAdd" /></th>
    </tr>
</table>
<asp:GridView runat="server" ID="gvNumber" AutoGenerateColumns="false">
    <Columns>
        <asp:BoundField DataField="ID" HeaderText="Number" />
    </Columns>
</asp:GridView>

Namespace

using System.Data;

Code

protected void BindGrid()
{
    DataTable dt = new DataTable();
    dt.Columns.AddRange(new DataColumn[1] { new DataColumn("Id", typeof(Int64)) });
    dt.Rows.Add(Convert.ToInt64(txtNUmber.Text));
    gvNumber.DataSource = dt;
    gvNumber.DataBind();
}

protected void OnAdd(object sender, EventArgs e)
{
    BindGrid();
}

Screenshot