Question

My web site uses a master page, where I’ve placed two controls, a TextBox and an ImageButton, they are intended to be viewed and accessible on all content sites. Here’s the aspx code in Site.Master:

<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<asp:ImageButton ID="ImageBtn" runat="server" ImageUrl="~/Image.png"
  PostBackUrl="~/Result.aspx"></asp:ImageButton>

Clicking the button should redirect the visitor to Result.aspx, which it does.

Result.aspx.cs has the following in the Page_Load event:

    protected void Page_Load(object sender, EventArgs e)
    {
        TextBox txbx = this.Master.FindControl("TextBox1") as TextBox;
        if (txbx != null)
        {
            Label1.Text = "Value: " + txbx.Text;
        }
        else
        {
            Label1.Text = "TextBox seems to be null";
        }
    }

The weird behavior appears when the image button is clicked the first time. The visitor gets this information from the page “Value: ” (i.e an empty string “”), even though a value was entered in TextBox1. The subsequent clicks presents the value(s) correctly, e.g “Value: SomeText”.

Why doesn’t the value “come along” the first time?

Is there a better way to ensure that?

• The visitor is redirected to Result.aspx AND
• that the value is “registered” and can be handled in Result.aspx.cs AND
• that a user will be redirected, if Result.aspx is entered without the use of the image buttons PostBackURL

I’ve tried IsPostBack but it seems to behave strangely when using a master page as previous page …

Very thankful for an answer!

Sincerely,

Mr Kay

Answer 1

If you are using PostBackURL on your ImageButton on the master page and come from another page you must use:

PreviousPage.Master.FindControl("TextBox1") as TextBox;

If you are on the PostBackURL page and click your ImageButton, you need to use

Master.FinControl("TextBox1") as TextBox;

(PreviousPage would be null in this case)

you could use something like this:

var txbx = PreviousPage == null ?
    Master.FindControl("TextBox1") as TextBox :
    PreviousPage.Master.FindControl("TextBox1") as TextBox;

See: http://msdn.microsoft.com/en-us/library/system.web.ui.page.previouspage(v=vs.100).aspx
at the Remarks section.