how to used store multiple data in textbox move single data

Question

how to used store multiple data in textbox in saparation in comma ,move single selected word in listbox using c# code 

 

------------------------- Source Code ----------------------------------------- 

 

<textarea ID="Textarea1" runat="server" rows="10" cols="50"></textarea>

 

<asp:ListBox style="text-align:right" ID="List2" runat="server" Height="100px" Width="300px"></asp:ListBox>

 

<asp:Button ID="Button1" runat="server" Text="Move Data" OnClick="Button1_Click1" /> 

 

 

-------------------------- Page Load Code----------------------

DataTable dt=null; 

 

if(ViewState["data"]==null)

{

DataTable dt = new DataTable();

dt.Columns.Add("ColumnID");

ViewState["data"] = dt;

}

 

 

 

----------------------- Button Code-------------------------------

 

protected void Button1_Click1(object sender, EventArgs e)

{

string str = Textarea1.Value.Trim();

dt = (DataTable)ViewState["data"];

dt.Rows.Add(str);

ViewState["data"] = dt;

List2.DataSource = dt;

List2.DataValueField = "ColumnID";

List2.DataBind();

}

 

please help me....