Selected row to textbox when clicked on row not firing - asp.net

Question

I can click on row to selected them but when i need them to textbox it's not firing i tried to use Autopostback on textbox but it's doesn't work i think it's because of for each that not make row.cells(0) work
i write a code like this
VB.NET
Protected Sub OnSelectedIndexChanged(sender As Object, e As EventArgs)
For Each row As GridViewRow In GridView1.Rows
If row.RowIndex = GridView1.SelectedIndex Then
row.BackColor = ColorTranslator.FromHtml("#E294FF")
txtrepname.Text = row.Cells(0).Text
row.ToolTip = String.Empty
Else
row.BackColor = ColorTranslator.FromHtml("#FFFFFF")
row.ToolTip = "Click to select this row."
End If
Next
End Sub
Gridview
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False"
DataSourceID="SqlDataSource1" ShowFooter="True" Width="1280px" OnRowDataBound = "OnRowDataBound" OnSelectedIndexChanged = "OnSelectedIndexChanged"
onrowupdating="GridView1_RowUpdating" DataKeyNames="REP_NAME" PageSize="9999">
<Columns>
<asp:TemplateField HeaderText="" >
<ItemTemplate>
<asp:LinkButton ID="lnkEdit" runat="server" Text="" CommandName="Edit" ToolTip="Edit"
CommandArgument=''><img src="Images/ad_edit.png" BORDER="0" /></asp:LinkButton>
<asp:LinkButton ID="lnkDelete" runat="server" Text="Delete" CommandName="Delete"
ToolTip="Delete" OnClientClick='return confirm("Are you sure you want to delete this entry?");'
CommandArgument='' BorderColor="#CC3300"><img src="Images/ad_delete.png" BORDER="0" /></asp:LinkButton>
</ItemTemplate>
<EditItemTemplate>
<asp:LinkButton ID="lnkInsert" runat="server" Text="" ValidationGroup="editGrp" CommandName="Update" ToolTip="Save"
CommandArgument=''><img src="Images/ad_save.png" BORDER="0" /></asp:LinkButton>
<asp:LinkButton ID="lnkCancel" runat="server" Text="" CommandName="Cancel" ToolTip="Cancel"
CommandArgument=''><img src="Images/ad_reload.png" BORDER="0" /></asp:LinkButton>
</EditItemTemplate>
<FooterTemplate>
<asp:LinkButton ID="lnkInsert" runat="server" Text="" ValidationGroup="newGrp" CommandName="InsertNew" ToolTip="Add New Entry"
CommandArgument=''><img src="Images/ad_add.png" BORDER="0"/></asp:LinkButton>
<asp:LinkButton ID="lnkCancel" runat="server" Text="" CommandName="CancelNew" ToolTip="Cancel"
CommandArgument=''><img src="Images/ad_reload.png" BORDER="0"/></asp:LinkButton>
</FooterTemplate>
<HeaderStyle Width="60px" />
</asp:TemplateField>
<asp:TemplateField HeaderText="Report Name" SortExpression="REP_NAME" >
<ItemTemplate>
<div style="overflow:hidden; text-overflow:ellipsis; white-space:nowrap; min-width:150px; ">
<asp:Label ID="Label1" runat="server" Text='<%# Bind("REP_NAME") %>'></asp:Label>
</div>
</ItemTemplate>
<EditItemTemplate>
<asp:Label ID="Label1" runat="server" Text='<%# Eval("REP_NAME") %>'></asp:Label>
</EditItemTemplate>
<FooterTemplate>
<asp:TextBox ID="txtREP_NAMENew" runat="server" CssClass="" Width="60px" ></asp:TextBox>
<asp:RequiredFieldValidator ID="valREP_FILEID" runat="server" ControlToValidate="txtREP_NAMENew"
Display="Dynamic" ErrorMessage="Province is required." ForeColor="Red" SetFocusOnError="True"
ValidationGroup="newGrp">*</asp:RequiredFieldValidator>
</FooterTemplate>
<HeaderStyle Width="80px" />
</asp:TemplateField>
</Columns>
</asp:GridView>