Save data in Temporary Table and do sorting to display in GridView using C# in ASP.Net

Hi Debug,

I have created a sample which full fill your requirement

HTML

<div>
    <table>
        <tr>
            <td>
                CustomerId:
            </td>
            <td>
                <asp:TextBox ID="txtCustomerId" runat="server" />
            </td>
        </tr>
        <tr>
            <td>
                Name:
            </td>
            <td>
                <asp:TextBox ID="txtName" runat="server" />
            </td>
        </tr>
        <tr>
            <td>
                Country:
            </td>
            <td>
                <asp:TextBox ID="txtCountry" runat="server" />
            </td>
        </tr>
        <tr>
            <td>
            </td>
            <td align="center">
                <asp:Button ID="btnSave" OnClick="Save" Text="Save" runat="server" />
            </td>
        </tr>
    </table>
    <br />
    <asp:GridView ID="gvDetails" runat="server" />
</div>

C#

DataTable dt = new DataTable();

protected void Page_Load(object sender, EventArgs e)
{
    dt.Columns.AddRange(new DataColumn[] { new DataColumn("CustomerId"), new DataColumn("Name"), new DataColumn("Country") });
    if (!IsPostBack)
    {
        BindGrid();
    }
}

private void BindGrid()
{
    dt.Rows.Add(2, "Mudassar Khan", "India");
    dt.Rows.Add(3, "Suzanne Mathews", "France");
    dt.Rows.Add(5, "Robert Schidner", "Russia");
    gvDetails.DataSource = dt;
    gvDetails.DataBind();
}

protected void Save(object sender, EventArgs e)
{
    dt.Rows.Add(txtCustomerId.Text.Trim(), txtName.Text.Trim(), txtCountry.Text.Trim());
    dt.DefaultView.Sort = "CustomerId";
    BindGrid();
}

Screenshot