Question

Basically I’m Trying to put out on the Textbox inside the Shared Function, But i didn’t access the Textbox inside the Shared Function Then i created an object of the _Default Class to access the Textbox.
After that i access the Textbox, but during running state it give me error NullReference, when i toggle i found that Textbox1.text = Nothing instead of Textbox1.text=””
Below is the Small Code which i made for sample

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles       
    Me.Load        
        TextBox1.Text = "123"        
        TestClass()        
    End Sub       

    Protected Shared Sub TestClass()       
        Dim MyF1 As New _Default       
        MyF1.TextBox1.Text = "ABC"       
    End Sub       

Answer 1

TextBox1 is an instance variable of your Page class, created (probably) by the ASP.NET designer.

Thus, you cannot access it in static/shared context.

When ASP.NET receives a request, it:

• creates an instance of your _Default class
• populates the controls of _Default class according to the data that comes from the client (e.g. form data)
• does a lot of other operations which are not relevant in this context

In your scenario, you create an instance of the _Default class, but don’t set any of its properties.

This results in the Textbox1 property being null and that’s why it throws NullreferenceException when used.

There are two possible solutions:

• mark the TestClass method as instance method (drop the Shared keyword)

• pass the current instance of _Default as a parameter to the static/shared method, like so:

  Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load        
      TextBox1.Text = "123"        
      TestClass(Me)        
  End Sub       
  
  Protected Shared Sub TestClass(currentPage as _Default)       
      currentPage.TextBox1.Text = "ABC"       
  End Sub 
  

The second solution requires that the TextBox1 property should be declared as public.

(sorry if there are any VB mistakes; I’m a C# programmer ☺)