Odd issue with textbox and ASP.NET

Question

This code was working properly before, basically I have a master page that has a single text box for searching, I named it searchBox. I have a method to pull the content of searchBox on form submit and set it to a variable userQuery. Here is the method:

Public Function searchString(ByVal oTextBoxName As String) As String
    If Master IsNot Nothing Then
        Dim txtBoxSrc As New TextBox
        txtBoxSrc = CType(Master.FindControl(oTextBoxName), TextBox)
        If txtBoxSrc IsNot Nothing Then
            Return txtBoxSrc.Text
        End If
    End If
    Return Nothing
End Function

The results are displayed on search.aspx. Now, however, if searchBox is filled and submitted on a page other than search.aspx, the contents of the text box are not passed through. The form is very simple, just:

<asp:TextBox ID="searchBox" runat="server"></asp:TextBox>
<asp:Button ID="searchbutton" runat="server" Text="search" UseSubmitBehavior="True" PostBackUrl="~/search.aspx" CssClass="searchBtn" />.

Answer 1

I think because you are using PostBackUrl, you are going to be required to use the "PreviousPage" identifier to reference your variable.

Another solution would to not use the PostBackUrl property and to capture the event within the user control (I'm assuming you are encapsulating this in one location) and then use the:

Response.Redirect("/search.aspx?sQuery=" & Server.URLEncode(searchBox.Text))

since you are not necessarily passing sensitive data, this should be acceptable as well.

Answer 2

I agree with Kyle as to why it doesn't work and the solution if you want to continue to access the value via the text control, but you can also pluck the form data out of the httprequest. I think like this (my asp.net is a bit rusty)

Request.Form[txtBoxSrc.UniqueID]

This plus other techniques (using the previouspage property) are documented here: http://msdn.microsoft.com/en-us/library/6c3yckfw(VS.80).aspx. It seems all you need to do is:

if (Page.PreviousPage != null)
{
    TextBox SourceTextBox = 
        (TextBox)Page.PreviousPage.FindControl("TextBox1");
    if (SourceTextBox != null)
    {
       return SourceTextBox.Text;
    }
}

Updated: Thanks to Jason Kealey for pointing out I needed to use UniqueID.