Question

I have a web form as

<asp:TextBox ID="txtname" runat="server" Text="Post on Next Page"/>
<asp:Button ID="btn1" runat="server" PostBackUrl="~/Page2.aspx" Text="Post on next page" />

Now on Page2.aspx the code-behind is as follows:

protected void Page_Load(object sender, EventArgs e)
{
   if(PreviousPage!=null && PreviousPage.IsCrossPagePostBack)
   {
       TextBox txt1 = (TextBox)PreviousPage.FindControl("txtname");
       label1.Text = "Value: " + txt1.Text;
   }
}

I end up getting the error object reference not set to instance of an object for txt1

Where label1 is a label used to display the output. However, the value is not displayed.

What step am i missing?

Answer 1

Try this

if (PreviousPage != null && PreviousPage.IsCrossPagePostBack)
            {
                //get the content place holder from master page of your previous page where your controls are placed
                //In this code the txtname textbox is placed inside ContentPlaceHolderID="MainContent"
                var cp =PreviousPage.Master.FindControl("MainContent") as ContentPlaceHolder;
                //find the textbox inside content place holder from previous page
                TextBox txt1 = cp.FindControl("txtname") as TextBox;
                label1.Text = "Value: " + txt1.Text;
            }