why a multiline textbox (inside a user control) is not holding its value after a postback? - asp.net

Question

I have a user control that have a gridview, buttons and a multi-line textbox for comments.
When the page posts back, Gridview is behaving normaly (its controls keeps their values after postback). However, the Comment textbox is always empty, no matter what I do.
protected void Page_Load(object sender, EventArgs e)
{
//This code is in the user ciontrol.
if (!IsPostBack)
{
string test = this.txtDepartmentComments.Text;
}
}
I put a break point at that line and the value is always empty. I've tried also to set the value in the code behind like:
protected void Page_Load(object sender, EventArgs e)
{
//This code is in the user ciontrol.
if (!IsPostBack)
{
this.txtDepartmentComments.Text = "Test!";
}
}
But when the page loads, the control remain empty.
Any idea why this is hapenning?
EDIT
This the ascx code (i.e. user control)
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns = "false" >
</asp:GridView>
<asp:TextBox ID="txtComments" runat="server" Columns="45" TextMode= "MultiLine"/>
<asp:Button ID="btnComplete" runat="server" Text="Completed"/>
And thid id the aspx (i.e. the parent page)
<asp:Repeater ID="rpNewHire" runat="server">
<HeaderTemplate>
<table>
</HeaderTemplate>
<ItemTemplate>
<tr>
<td>
<user:MyUserControl ID = "MyUserControl1" runat = "server"
DepartmentID= '<%# Eval("DepID")%>'><user:MyUserControl />
</td>
</tr>
</ItemTemplate>
<FooterTemplate>
</table>
</FooterTemplate>
</asp:Repeater>

Answer 1

if(!IsPostBack) is for reading values from controls after postback, you are trying to read text box value on initial load which will always be empty, remove the '!' from your condition. Also it is hard to debug your issue with out the aspx page contents, try posting the design part as well in your question.
EDIT
Your user tag is not well formatted inside repeater, it is missing closing tag and runat attribute
<user:MyUserControl runat="server" ID = "MyUserControl1" DepartmentID= '<%# Eval("DepID")%>'></user:MyUserControl>
Controls inside repeater cannot be accessed directly, you have to loop through the rows of the repeater and find your child controls and then try reading values from them, that after you bind some data to the repeater.
Check this http://msdn.microsoft.com/en-us/magazine/cc163780.aspx

Answer 2

Page's IsPostBack and each user controls' IsPostBack are not same.
When a user control is posted back, that particular control's IsPostBack is true, but other user controls' IsPostBack are still false.
You can use explicitly !Page.IsPostBack inside a user control to check whether its parent page is posted back or not.
if(!Page.IsPostBack){
// do something
}
Dynamically Loaded Control can not maintain values at PostBack? It is not directly related to your question, but it might be useful for you.