destroy row data while create new row inside gridview

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C#

ASP.NET

Gridview

Hi,

I am using radControl Radgrid and trying to create a dynamic row inside gridview but when I create a new row on click of newitem button then last row of data is destroyed.

After inserting data in new row again click on newitem button again all data destroyed.

Please tell me the reason.
If there are any solutions please let me know.

Thanks

aspx code is

<asp:Button ID="btnAdd" runat="server" Text="Add" OnClick="btnAdd_click" Width="70px" />
<br />
<telerik:RadGrid ShowFooter="true" ID="radGrid1" runat="server" OnInsertCommand="radGrid1_InsertCommand"
OnPreRender="radgrid1_PreRender" AutoGenerateColumns="False" GridLines="None"
AutoGenerateEditColumn="true" AllowAutomaticUpdates="true" AllowMultiRowEdit="True" AllowAutomaticInserts="true"
OnItemDataBound="radGrid1_ItemDataBound" OnNeedDataSource="radGrid1_NeedDataSource">
<MasterTableView EditMode="EditForms" PageSize="5" CommandItemDisplay="None">
<Columns>
<telerik:GridTemplateColumn DataField="rowNumber" HeaderText="S.No.">
<ItemTemplate>
<asp:Label ID="lblrowNumber" runat="server" Text='<%#Eval("rowNumber")%>'></asp:Label>
</ItemTemplate>
</telerik:GridTemplateColumn>

<telerik:GridTemplateColumn UniqueName="Product_Name" ReadOnly="true" HeaderText="Product Name">
<ItemTemplate>
<asp:DropDownList ID="ddl1" runat="server" AutoPostBack="true" DataTextField="product_Name"
DataValueField="product_Name" OnSelectedIndexChanged="ddl1_SelectedIndexChanged">
</asp:DropDownList>
</ItemTemplate>
</telerik:GridTemplateColumn>
<telerik:GridTemplateColumn UniqueName="Product_Rate" ReadOnly="true" HeaderText="Product Rate">
<ItemTemplate>
<asp:Label ID="lblRate" runat="server" Text='<%#Eval("Product_Rate") %>'></asp:Label>
</ItemTemplate>
</telerik:GridTemplateColumn>
<telerik:GridTemplateColumn UniqueName="Product_Quantity" HeaderText="Product Quantity">
<ItemTemplate>
<telerik:RadNumericTextBox ID="txtQuantity" AutoPostBack="true" runat="server" OnTextChanged="txtQuantity_TextChanged">
</telerik:RadNumericTextBox>
</ItemTemplate>
</telerik:GridTemplateColumn>
<telerik:GridTemplateColumn UniqueName="Product_Amount" ReadOnly="true" HeaderText="Product Amount">
<ItemTemplate>
<asp:Label ID="lblAmount" runat="server"></asp:Label>
</ItemTemplate>
<FooterStyle HorizontalAlign="Right" />
<FooterTemplate>
<asp:Button ID="btnNewRow" runat="server" Visible="true" Text="Add Item" OnClick="btnNewRow_click" /></FooterTemplate>
</telerik:GridTemplateColumn>
</Columns>
</MasterTableView>
</telerik:RadGrid>
<table border="0" cellpadding="0" cellspacing="0" width="100%">
<tr>
<td align="center">
<center>
<asp:Button ID="btnSubmit" runat="server" Text="Submit" OnClick="Submit" />
<asp:Button ID="Button1" runat="server" Text="Clear" OnClick="Clear" />
</center>
</td>
</tr>
</table>


css code is...

public partial class Test_Order : System.Web.UI.Page
{
DataTable dt = new DataTable();
TableRow dr;

protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
create_datatable();
}
}
public void create_datatable()
{

dr = new TableRow();
dt.Columns.Add(new DataColumn("rowNumber", typeof(string)));
dt.Columns.Add("Product_Name");
dt.Columns.Add("Product_Rate");
dt.Columns.Add("Product_Quantity");
dt.Columns.Add("Product_Amount");
ViewState["Address"] = dt;

radGrid1.DataSource = dt;
radGrid1.DataBind();

}

protected void radGrid1_NeedDataSource(object source, GridNeedDataSourceEventArgs e)
{
SqlConnection connection = new SqlConnection();
connection = new SqlConnection(ConfigurationManager.ConnectionStrings["chalk_hillConnectionString"].ConnectionString);
SqlDataAdapter da = new SqlDataAdapter();
da.SelectCommand = new SqlCommand("select product_id,product_name from product_detail", connection);


for (int i = 0; i < dt.Rows.Count; i++)
{
dt.Rows.Add(dr);
dt.AcceptChanges();
try
{
da.Fill(dt);
}
finally
{
connection.Close();
}
}
radGrid1.DataSource = dt;

}

protected void radGrid1_ItemDataBound(object sender, GridItemEventArgs e)
{
if (e.Item is GridDataItem)
{
GridDataItem item = (GridDataItem)e.Item;
DropDownList list = (DropDownList)item.FindControl("ddl1");
list.Items.Insert(0, new ListItem("select", "-1"));
SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["chalk_hillConnectionString"].ConnectionString);
SqlDataAdapter da = new SqlDataAdapter();
da.SelectCommand = new SqlCommand("select product_id,product_name from product_detail", con);
DataSet ds = new DataSet();
da.Fill(ds);
if (ds != null)
{
list.DataSource = ds;
list.DataTextField = "product_name";
list.DataValueField = "product_id";
list.DataBind();
}
list.Items.Insert(0, new ListItem("Select Item..", "0"));
list.SelectedIndex = 0;
}
}

protected void radGrid1_InsertCommand(object sender, EventArgs e)
{
isinsert = true;
}
protected void ddl1_SelectedIndexChanged(object sender, EventArgs e)
{
DropDownList list = (DropDownList)sender;
GridDataItem item = (GridDataItem)list.NamingContainer;
SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["chalk_hillConnectionString"].ConnectionString);
con.Open();
SqlCommand cmd = new SqlCommand("select product_rate from product_detail where product_name='" + list.SelectedItem.Text + "'", con);
SqlDataReader reader; ;
reader = cmd.ExecuteReader();
if (reader.Read())
{
(item.FindControl("lblRate") as Label).Text = reader["product_rate"].ToString();
}

}

protected void txtQuantity_TextChanged(object sender, EventArgs e)
{
RadNumericTextBox textQuantity = sender as RadNumericTextBox;

GridEditableItem item = textQuantity.NamingContainer as GridEditableItem;
Label lbl1 = item["Product_Rate"].FindControl("lblRate") as Label;
Label lbl3 = item["Product_Amount"].FindControl("lblAmount") as Label;
lbl3.Text = (int.Parse(lbl1.Text) * int.Parse(textQuantity.Text)).ToString();
create_datatable_row();

}
protected void btnNewRow_click(object sender, EventArgs e)
{
AddNewRowToGrid();
}

private void AddNewRowToGrid()
{

if (ViewState["Address"] != null)
{
DataTable dtCurrenttable = (DataTable)ViewState["Address"];
DataRow drCurrentRow = null;
if (dtCurrenttable.Rows.Count > 0)
{
drCurrentRow = dtCurrenttable.NewRow();
drCurrentRow["rowNumber"] = dtCurrenttable.Rows.Count + 1;
dtCurrenttable.Rows.Add(drCurrentRow);
ViewState["Address"] = dtCurrenttable;
radGrid1.DataSource = dtCurrenttable;
radGrid1.DataBind();
}
}
else
{
Response.Write("ViewState is null");
}
}

//for display blank grid on button click creation....

protected void btnAdd_click(object sender, EventArgs e)
{

dt = (DataTable)ViewState["Address"];
if (dt.Rows.Count != 0)
{
if (dt.Columns.Count != 0)
{
create_datatable();
}
else
{
create_datatable_row();
}
}
DataRow dr = dt.NewRow();
dr["rowNumber"] = 1;
dt.Rows.Add(dr);
radGrid1.DataSource = dt;
radGrid1.DataBind();
}
private void create_datatable_row()
{
DataRow dr = dt.NewRow();
dt.Rows.Add(dr);
}
bool isinsert = false;
protected void radgrid1_PreRender(object sender, EventArgs e)
{
if (isinsert)
{
isinsert = false;
radGrid1.MasterTableView.IsItemInserted = true;
radGrid1.MasterTableView.Rebind();
}

}


}

now just gothrough and tell me the issue actually i am not very much aware gridview i doing my task with the help of books and this forum. i am new in development.