Gridview: Change Button Text and link on Page load - asp.net

Question

Gurus,
I have a gridview with the template field button and I want to change text on the button on the user type on page load.
I am trying to get the button from Gridview to change the text and link but the control always return null. It will be really helpful to understand how to change the text and link on page load.
TryCast(row.Cells(0).Controls(0).FindControl("idAppearButton"),
Button)
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Trim(Request.QueryString("Msg")) <> "" Then
If InStr(Request.QueryString("Msg"), "<") > 0 Then
Response.Write(Mid(Request.QueryString("Msg"), 1, InStr(Request.QueryString("Msg"), "<")))
Else
Response.Write(Request.QueryString("Msg"))
End If
End If
If Page.IsPostBack = False Then
Dim sSeries As String
sSeries = "Aim NBDE Part 1"
Dim o_cmd As SqlCommand
Dim o_reader As SqlDataReader
o_Con = New SqlConnection(GlobalVarC.DataS)
o_Con.Open()
Dim ds As New Data.DataSet
Dim da As SqlDataAdapter
Dim ExamId As String
S_Sql = "SELECT SNo from Exam_Ser where Series='" & sSeries.ToString & "'"
o_cmd = New SqlCommand(S_Sql, o_Con)
o_reader = o_cmd.ExecuteReader
ExamId = ""
Dim ExamIdTmp As String
While o_reader.Read
If ExamId.Equals("") Then
ExamId = ExamId + "SNo = "
Else
ExamId = ExamId + " OR SNo = "
End If
ExamIdTmp = o_reader(0).ToString
ExamId = ExamId + ExamIdTmp
ExamId = ExamId + ""
End While
o_reader.Close()
o_cmd.Dispose()
S_Sql = "SELECT Name from Exam where " & ExamId.ToString
da = New SqlDataAdapter(S_Sql, o_Con)
da.Fill(ds)
GridSubject.DataSource = ds
GridSubject.DataBind()
da.Dispose()
ds.Dispose()
o_Con.Close()
For Each row As GridViewRow In GridSubject.Rows
Dim button As Button
'button = TryCast(row.Cells(0).Controls(0).FindControl("idAppearButton"), Button)
'button.Text = "Buy"
Next
End If
End Sub
<asp:GridView ID="GridSubject" runat="server" AutoGenerateColumns="False" CellPadding="3"
OnSelectedIndexChanged="GridSubject_SelectedIndexChanged" BackColor="#CCCCCC"
BorderColor="#E7E7FF" BorderStyle="None" BorderWidth="1px"
Width="714px" GridLines="Horizontal"
>
<EditRowStyle Font-Names="Calibri" />
<EmptyDataRowStyle Font-Names="Calibri" />
<FooterStyle BackColor="#B5C7DE" ForeColor="#4A3C8C" Font-Names="Calibri" />
<AlternatingRowStyle BackColor="#F7F7F7" Font-Names="Calibri" />
<Columns >
<asp:BoundField DataField="Name" HeaderText="Exam Name">
<ItemStyle Width="140px" HorizontalAlign="Left" VerticalAlign="Top" />
<HeaderStyle HorizontalAlign="Left" />
</asp:BoundField>
<asp:TemplateField ItemStyle-Width="100px">
<ItemTemplate>
<asp:RadioButtonList ID="RadioButtonList1" runat="server">
<asp:ListItem Value="0">Part 1</asp:ListItem>
<asp:ListItem Value="1">Part 2</asp:ListItem>
<asp:ListItem Selected="True" Value="3">Part 1 & 2</asp:ListItem>
</asp:RadioButtonList>
</ItemTemplate>
<FooterStyle HorizontalAlign="Left" />
<HeaderStyle HorizontalAlign="Left" />
<ItemStyle Width="100px" HorizontalAlign="Left"></ItemStyle>
</asp:TemplateField>
<asp:TemplateField ShowHeader="False">
<ItemTemplate>
<asp:Button ID="idAppearButton" runat="server"
CommandName="MYCOMMAND" Text="Appear">
</asp:Button>
</ItemTemplate>
</asp:TemplateField>
<asp:ButtonField ButtonType="Button" CommandName="ViewResults" Text="Results" >
<HeaderStyle HorizontalAlign="Center" VerticalAlign="Top" />
</asp:ButtonField>
<asp:TemplateField HeaderText="Status">
<ItemTemplate>
<asp:Label runat="server" Text="Not Completed"></asp:Label>
</ItemTemplate>
</asp:TemplateField>
</Columns>
<RowStyle BackColor="#E7E7FF" ForeColor="#000000" Font-Names="Calibri" />
<SelectedRowStyle BackColor="#738A9C" Font-Bold="True" ForeColor="#F7F7F7"
Font-Names="Cambria" />
<PagerStyle BackColor="#E7E7FF" ForeColor="#4A3C8C" HorizontalAlign="Right"
Font-Names="Calibri" />
<HeaderStyle BackColor="#000000" Font-Bold="True" ForeColor="#F7F7F7" />
<SortedAscendingCellStyle BackColor="#F1F1F1" />
<SortedAscendingHeaderStyle BackColor="#808080" />
<SortedDescendingCellStyle BackColor="#CAC9C9" />
<SortedDescendingHeaderStyle BackColor="#383838" />
<SortedAscendingCellStyle BackColor="#F4F4FD"></SortedAscendingCellStyle>
<SortedAscendingHeaderStyle BackColor="#5A4C9D"></SortedAscendingHeaderStyle>
<SortedDescendingCellStyle BackColor="#D8D8F0"></SortedDescendingCellStyle>
<SortedDescendingHeaderStyle BackColor="#3E3277"></SortedDescendingHeaderStyle>
</asp:GridView>

Answer 1

You have to use Row.FindControl(id) to find the reference to the control. You cannot use Cell.Text if you use TemplateFields, that works only with BoundFields:
button = DirectCast(row.FindControl("idAppearButton"), Button)