I am having a problem of adding data into a grid. wherever i click a button to add an item into a grid, it always add remain the last item i add only. Here is some of my code, i am thikning is the post back problem but i do not know where to place the post back.

Here is some of my code:

DataTable dt = new DataTable();
DataView dv = new DataView();
DataRow dr;

protected System.Web.UI.WebControls.DataGrid dg;
protected System.Web.UI.WebControls.DropDownList ddlOption;
protected System.Web.UI.WebControls.Button Button1;

private void Page_Load(object sender, System.EventArgs e)
{
  OpenTable();
  InitializeDropdown();
  if (!IsPostBack)
  {
    InitializeDataGrid();
  }
}

public void InitializeDropdown()
{
  if (!IsPostBack)
  {
    ArrayList values = new ArrayList();
      values.Add ("id 1");
      values.Add ("id 2");
      values.Add ("id 3");
      values.Add ("id 4");
      values.Add ("id 5");

    ddlOption.DataSource = values;
    ddlOption.DataBind();
  }
}

public void OpenTable()
{
  dt = new DataTable();
  dt.Columns.Add(new DataColumn("id", typeof(string)));
}

public void InitializeDataGrid()
{
  dv = new DataView(dt);

  dg.DataSource = dv;
  dg.DataBind();
}

private void Button1_Click(object sender, System.EventArgs e)
{
  dr = dt.NewRow();

  dr[0] = ddlOption.SelectedItem;
  dt.Rows.Add(dr);

  InitializeDataGrid();
  dg.DataBind();
}

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The reason you are getting the last value selected because each time on click of button you are creating one row with the selected dropdown list item only.You are not retaining the previous row values.
To retain the previous row values which you have added ,create an static string variable and concat the selected value to it.See the logic below..


private void Button1_Click(object sender, System.EventArgs e)
{
if(s.Length==0) {
    s = Convert.ToString(DropDownList1.SelectedItem);
}
else{
     s = s +","+DropDownList1.SelectedItem;
}
string[] sr=s.Split(',');
for(int j=0;j<sr.Length ;j++){
    dr = dt.NewRow();
    dr[0] = sr[j];
    dt.Rows.Add(dr);
}
InitializeDataGrid();
DataGrid1.DataBind();
}

    Here i have concatenated the selected items with the ',' delimiter
and i created the sr array with it.I have created rows with that collection.This is one way of retaining the rows.