Question

Please help me to figure out what is wrong with this code:

I have ASP.NET page with one button visible.

When user clicks it – it instances MyClass (its implementation is in AppCode directory) and turns invisible (button2 becomes visible).

When I click button2 it raises “Object reference not set to an instance of an object” Exception.

What seems to be the problem?

{
    public MyClass noviTest;

    protected void Page_Load(object sender, EventArgs e)
    {
    }

    protected void Button1_Click(object sender, EventArgs e)
    {
        noviTest = new MyClass(TextBox1.Text);
        Button1.Visible = false;
        Button2.Visible = true;
    }

    protected void Button2_Click(object sender, EventArgs e)
    {
        Label1.Text=noviTest.getID; //this is the critical line
    }
}

Answer 1

Since on postback the noviTest reference to MyClass is not recreated.

You can add it to the viewstate to keep a reference to it. (Assuming MyClass is serializable).
In Button1_Click:

ViewState("noviTest") = noviTest;

Then in Button2_Click:

var noviTest = ViewState("noviTest");