从textbox.text插入gridview

Question

I have a gridview control and I want to input a value to a textbox and click button so that it inserts a value from textbox.text to the gridview. I use this code:

    <asp:TextBox ID="txtName" runat="server" ViewStateMode="Enabled"></asp:TextBox>
    <br />
    <asp:Button ID="btnAddName" runat="server" Text="Button" 
        onclick="btnAddName_Click" />
    <br />
    <br />
    <asp:GridView ID="gvName" runat="server" ViewStateMode="Enabled">
    <Columns>
    <asp:TemplateField>
    <ItemTemplate>
    <asp:Label ID="lblName" runat="server"></asp:Label>
    </ItemTemplate>
    </asp:TemplateField>
    </Columns>
    </asp:GridView>

and:

protected void btnAddName_Click(object sender, EventArgs e)
    {

        DataTable dt = new DataTable();
        dt.Columns.Add(new DataColumn("lblName", typeof(string)));
        DataRow _dr = dt.NewRow();
        _dr["lblName"] = txtName.Text;
        dt.Rows.Add(_dr);

        gvName.DataSource = dt;
        gvName.DataBind();
    }

I input the text in the textbox and click on the button to insert a value to the gridview. It works ok, but on the second step, after page postback it lost previous data in the gridview.

I want to not lose the previous data in the gridview. Please help me.

Answer 1

You need to add row to original source you are binding to GridView . if you create new table each time you click button and bind that to gridview , it will show data from new DataTable and old data.

try this

  protected void btnAddName_Click(object sender, EventArgs e)
  {
    DataTable dt;
    if(Session["dt"] == null)
    {
        dt = new DataTable();
        dt.Columns.Add(new DataColumn("lblName", typeof(string)));
    }
    else
    {
        dt = (DataTable)Session["dt"];
    }

    DataRow _dr = dt.NewRow();
    _dr["lblName"] = txtName.Text;
    dt.Rows.Add(_dr);

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

    Session["dt"] = dt; 
   //store dt in session so that you can reuse it again after postback
 }

Answer 2

Are you checking in your Page_Load Method if your page is in PostBack mode?

if(IsPostBack) { //Load the data for the first time }

If not, your originally and "old" data will be bind to the gridview.

Update: To reuse the old data, store the datatable in a session variable, load it from there, add the new line and bind data datatable again.