c# - When does a Gridview have a null DataSource? -

i've read multiple sources gridview's not persist gridview.datasource property on postback. understanding in term's of asp.net, postback page load not first pageload (see msdn).

i've got situation 2 similar gridviews.

gvone.datasource null on postback.
gvtwo.datasource not null on postback.

the big difference outside of few differing columns gvone populated entity framework , linq. gvtwo populated datatable filled sqldataadapter.

further, gvone , gvtwo have templatefield textbox use gather user input. both use same code pull textbox.text on postback:

textbox tb = (textbox)gvone.rows[i].findcontrol("actualtxt"); 

gvone gathers tb.text. gvtwo always finds tb.text value 0.

basic gridview code:

<asp:gridview id="gvone" runat="server" autogeneratecolumns="false">         <columns>         <asp:templatefield headertext="return">    <itemtemplate>    <asp:textbox id="actualtxt" runat="server" text='0' width="40px"></asp:textbox>    </itemtemplate>              </asp:templatefield>           ...         </columns> </asp:gridview>  <asp:gridview id="gvtwo" runat="server" autogeneratecolumns="false">         <columns>         <asp:templatefield headertext="order">    <itemtemplate>    <asp:textbox id="actualtxt" runat="server" text='0' width="40px"></asp:textbox>    </itemtemplate>              </asp:templatefield>            ...         </columns> </asp:gridview> 

changing gvtwo use entity framework , linq potential solution, albeit major undertaking. know going on here?

update (see comment on joel etherton's answer) due popular demand here code populate gridview within page_load event gvtwo (gvone similar):

   ordersgv.datasource = datasetobject.tables["activeparts"];     ordersgv.databind(); 

searching through code behind found no other references ordersgv.datasource , no other events hooked associated page life cycle.

gridviews not persist datasource across postbacks. if have gridview has non-null datasource must filling datasource somewhere in code. instructive travel through event cycle find population of datasource occuring on postback.