Question

Im trying to pass a value of a date control from form1 to form2.

on form 1.aspx.vb:

   Public ReadOnly Property Property1() As Date
        Get
            Return StartDate.SelectedDate
        End Get
    End Property

On Form2.aspx:

<%@ PreviousPageType VirtualPath="~/form1.aspx" %> 

On form2.aspx.vb:

 Label14.Text = PreviousPage.Property1

when I run it, the compiler gives me an error:

"Object reference not set to an instance of an object."

with marking in red:

Label14.Text = PreviousPage.Property1

Tried to assign the property to a string, it did not work either.

Any suggestions ???

Regards.

Answer 1

When the Form2.aspx page is accessed directly without cross-page posting, then PreviousPage property is null. You should add this check before retrieving value of Property1:

if (PreviousPage != null && PreviousPage.IsCrossPagePostBack) {
    Label14.Text = PreviousPage.Property1
}

Using PreviousPageType VirtualPath=”~/form1.aspx” directive is a little bit dangerous when other page than Form1.aspx do cross-page post to Form2. PreviousPage property throws InvalidCastException (it expects Form1 page but it gets something else).

For more information see: http://msdn.microsoft.com/en-us/library/ms178139.aspx.