How to add new row in a gridview on button click - asp.net

Question

I am new to asp.net and i want to add new row in a gridview on button click... see my code kindly help me..its been 2 days i am working on it but didn't find the solution....
HTML CODE
<div>
<asp:GridView ID="GridView1" runat="server" ShowFooter="true" AutoGenerateColumns="false"
DataKeyNames="PRODUCTID" CellPadding="3" GridLines="Both" OnRowEditing="gridOnRowEditing"
OnRowCancelingEdit="gridOnRowCancelingEdit" OnRowUpdating="gridOnRowUpdating">
<HeaderStyle BackColor="Cyan" ForeColor="White" BorderColor="Red" />
<Columns>
<asp:CommandField ButtonType="Button" ShowCancelButton="true" ShowEditButton="true"
HeaderText="Edit & Update" />
<asp:BoundField DataField="PRODUCTID" HeaderText="PRODUCT ID" ReadOnly="true" />
<asp:TemplateField HeaderText="PRODUCT NAME">
<ItemTemplate>
<asp:TextBox runat="server" ID="txtProduct1" Text='<%# Eval("PRODUCTNAME") %>'></asp:TextBox>
</ItemTemplate>
<EditItemTemplate>
<asp:TextBox runat="server" ID="txtProduct" Text='<%# Eval("PRODUCTNAME") %>'></asp:TextBox>
</EditItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="UNIT PRICE">
<ItemTemplate>
<asp:TextBox runat="server" ID="txtPrice1" Text='<%# Eval("UNITPRICE") %>'></asp:TextBox>
</ItemTemplate>
<EditItemTemplate>
<asp:TextBox runat="server" ID="txtPrice" Text='<%# Eval("UNITPRICE") %>'></asp:TextBox>
</EditItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
<asp:Button runat="server" OnClick="button1_click" ID="button1" Text="Add New Row" />
<%-- <input type="button" id="btnNew" value="Add New" onclick="addNew()" />--%>
</div>
C SHARP CODE
public partial class WebForm1 : System.Web.UI.Page
{
SqlConnection con = new SqlConnection("Data Source=localhost;Initial Catalog=practice;Integrated Security=true;");
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
BindData();
}
}
protected void BindData()
{
SqlDataAdapter sda = new SqlDataAdapter("Select * From PRODUCTDETAILS order by PRODUCTID asc", con);
DataTable dt = new DataTable();
sda.Fill(dt);
GridView1.DataSource = dt;
GridView1.DataBind();
ViewState["CurrentTable"] = dt;
}
protected void gridOnRowEditing(object sender, GridViewEditEventArgs e)
{
GridView1.EditIndex = e.NewEditIndex;
BindData();
}
protected void gridOnRowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
{
GridView1.EditIndex = -1;
BindData();
}
protected void gridOnRowUpdating(object sender, GridViewUpdateEventArgs e)
{
GridViewRow row = (GridViewRow)GridView1.Rows[e.RowIndex];
TextBox txtProductName = (TextBox)row.FindControl("txtProduct");
TextBox UNITPRICE = (TextBox)row.FindControl("txtPrice");
string ProductName = txtProductName.Text;
string txtUnitPrice = UNITPRICE.Text;
int ProductID = Convert.ToInt32(GridView1.DataKeys[e.RowIndex].Value);
UpdateRecord(ProductID, ProductName, txtUnitPrice);
}
protected void UpdateRecord(int ProductID, string ProductName, string UnitPrice)
{
try
{
SqlCommand cmd = new SqlCommand("Update PRODUCTDETAILS set ProductName=#ProductName,UnitPrice=#UnitPrice WHERE ProductID=#ProductID", con);
cmd.Parameters.Add(new SqlParameter("#ProductID", ProductID));
cmd.Parameters.Add(new SqlParameter("#ProductName", ProductName));
cmd.Parameters.Add(new SqlParameter("#UnitPrice", UnitPrice));
con.Open();
cmd.ExecuteNonQuery();
con.Close();
GridView1.EditIndex = -1;
BindData();
}
catch (Exception ex)
{
throw ex;
}
}
protected void AddNewRow()
{
//dt = new DataTable();
//DataRow dr = null;
//dt.Columns.Add(new DataColumn("PRODUCTID", typeof(string)));
//dt.Columns.Add(new DataColumn("PRODUCTNAME", typeof(string)));
//dt.Columns.Add(new DataColumn("UNITPRICE", typeof(string)));
//dr = dt.NewRow();
//dr["PRODUCTID"] = 14;
//dr["PRODUCTNAME"] = string.Empty;
//dr["UNITPRICE"] = string.Empty;
//dt.Rows.Add(dr);
//ViewState["CurrentTable"] = dt;
//GridView1.DataSource = dt;
//GridView1.DataBind();
int rowIndex = 0;
if (ViewState["CurrentTable"] != null)
{
DataTable dtCurrentTable = (DataTable)ViewState["CurrentTable"];
DataRow drCurrentRow = null;
if (dtCurrentTable.Rows.Count > 0)
{
for (int i = 1; i <= dtCurrentTable.Rows.Count; i++)
{
int ProductID = Convert.ToInt32(GridView1.DataKeys[rowIndex].Value);
TextBox TextBoxName = (TextBox)GridView1.Rows[rowIndex].Cells[2].FindControl("txtProduct1");
TextBox TextBoxPrice = (TextBox)GridView1.Rows[rowIndex].Cells[3].FindControl("txtPrice1");
drCurrentRow = dtCurrentTable.NewRow();
drCurrentRow["PRODUCTID"] = ProductID + 1;
drCurrentRow["PRODUCTNAME"] = TextBoxName.Text;
drCurrentRow["UNITPRICE"] = TextBoxPrice.Text;
//dtCurrentTable.Rows[13 - 1]["PRODUCTID"] = ProductID + 1;
rowIndex++;
}
dtCurrentTable.Rows.Add(drCurrentRow);
ViewState["CurrentTable"] = dtCurrentTable;
GridView1.DataSource = dtCurrentTable;
GridView1.DataBind();
}
}
}
protected void button1_click(object sender, EventArgs e)
{
AddNewRow();
}
}
}