Add dynamic rows to GridView and export to Word document in ASP.Net

It seem that you are having TemplateField. Please use BoundField instead.

And you have to save the file first and then open it.

HTML:

<form id="form1" runat="server">
    <div>
        <table border="0" cellpadding="0" cellspacing="0">
            <tr>
                <td>
                    Name
                </td>
                <td>
                    <asp:TextBox ID="txtName" runat="server" />
                </td>
            </tr>
            <tr>
                <td>
                    LastName
                </td>
                <td>
                    <asp:TextBox ID="txtLastName" runat="server" />
                </td>
            </tr>
            <tr>
                <td>
                    Cell
                </td>
                <td>
                    <asp:TextBox ID="txtCell" runat="server" />
                </td>
            </tr>
            <tr>
                <td colspan="2" align="left">
                </td>
            </tr>
        </table>
        <br />
        <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" Font-Names="Arial"
            Font-Size="11pt" AlternatingRowStyle-BackColor="#C2D69B" HeaderStyle-BackColor="green">
            <Columns>
                <asp:BoundField ItemStyle-Width="150px" DataField="Name" HeaderText="Name" />
                <asp:BoundField ItemStyle-Width="150px" DataField="LastName" HeaderText="LastName" />
                <asp:BoundField ItemStyle-Width="150px" DataField="Cell" HeaderText="Cell" />
            </Columns>
        </asp:GridView>
        <asp:Button ID="btnExportToWord" runat="server" Text="Export to Word" OnClick="ExportToWord" />
        <br />
        <asp:Button Text="Add" OnClick="Add" runat="server" />
    </div>
    </form>

You need to add this code in the page load without this GridView will not be exported:

protected void Page_Load(object sender, EventArgs e)
    {
        if (Session["myDatatable"] != null)
        {
            DataTable dt = (DataTable)Session["myDatatable"];
            GridView1.Visible = true;
            GridView1.DataSource = dt;
            GridView1.DataBind();
            btnExportToWord.Visible = true;
        }
    }

 Other function and event.

 public void AddNewData()
    {
        DataTable dt = new DataTable();
        if (Session["myDatatable"] != null)
        {
            dt = (DataTable)Session["myDatatable"];
        }
        else
        {
            dt.Columns.Add("Name");
            dt.Columns.Add("LastName");
            dt.Columns.Add("Cell");
        }

        DataRow drow = dt.NewRow();
        drow["Name"] = this.txtName.Text.Trim();
        drow["LastName"] = this.txtLastName.Text.Trim();
        drow["Cell"] = this.txtCell.Text.Trim();
        dt.Rows.Add(drow);
        Session["myDatatable"] = dt;
        this.txtName.Text = string.Empty;
        this.txtLastName.Text = string.Empty;
        this.txtCell.Text = string.Empty;
    }

    public void BindMyGridview()
    {
        if (Session["myDatatable"] != null)
        {
            DataTable dt = (DataTable)Session["myDatatable"];

            if ((dt != null) && (dt.Rows.Count > 0))
            {
                GridView1.Visible = true;
                GridView1.DataSource = dt;
                GridView1.DataBind();
                btnExportToWord.Visible = true;
            }
            else
            {
                GridView1.Visible = false;
                btnExportToWord.Visible = false;
            }
        }

    }

    protected void Add(object sender, EventArgs e)
    {
        AddNewData();
        BindMyGridview();
    }
    public override void VerifyRenderingInServerForm(Control control)
    {
        /* Verifies that the control is rendered */
    }
    protected void ExportToWord(object sender, EventArgs e)
    {
        Session["myDatatable"] = null;
        Response.Clear();
        Response.Buffer = true;
        Response.AddHeader("content-disposition", "attachment;filename=GridViewExport.doc");
        Response.Charset = "";
        Response.ContentType = "application/vnd.ms-word ";
        StringWriter sw = new StringWriter();
        HtmlTextWriter hw = new HtmlTextWriter(sw);
        GridView1.AllowPaging = false;
        GridView1.DataBind();
        GridView1.RenderControl(hw);
        Response.Output.Write(sw.ToString());
        Response.Flush();
        Response.End();        

    }

Image:

Thank You.