Question

I am receiving this error message when I debug my program.

Object reference not set to an instance of an object.

That error happens on this line:

protected void Page_Load(object sender, EventArgs e)
{
bool x = (bool)Session["IsConnectionInfoSet"];--> error here
if (IsPostBack && x)
//do something with the bool x variable
}

Postback is invoked by:

protected void btnDo_Click(object sender, EventArgs e)
{
//do something
Session["IsConnectionInfoSet"] = true;
//do something
}

This error happened in Visual Studio 2008, .NET Framework 3.5.

Can someone give me advice on how this?

Answer 1

The Page_Load method is always run before any event handlers. As a result, the page_load will run, find null and throw an error, all before you click handler has a chance to set this session value.

Here’s a safer way to access this session value

bool x = Session["IsConnectionInfoSet"] == null ? false :
          (bool)Session["IsConnectionInfoSet"];