Find Controls inside GridView

// grid view defination

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" BackColor="PapayaWhip"  BorderColor="Black" BorderStyle="Solid" BorderWidth="1px" CellPadding="3" Font-Names="Tahoma" Height="16px"

Width="928px">

<Columns>

<asp:TemplateField>

<HeaderTemplate>HeadingHeaderTemplate>

<ItemTemplate>

<asp:TextBox ID="text_box1" runat="server">asp:TextBox>

ItemTemplate>

asp:TemplateField>

asp:GridView>

//code for accessing value of text_box1 inside the GridView1

  for(int i = 0;i<GridView1.Rows.Count; i++)

  {

    TextBox t1;

    t1 = (TextBox)GridView1.Rows[n].FindControl("text_box1");

    Response.Write(t1.Text);

  }