CODEWITHSUNDEEP
c#asp.net
millie
millie

Reputation: 2905

ASP.Net: GridView control and combobox woes part 2

This is a follow up to: ASP.Net: GridView control and combobox woes

I've implemented my code as kd7 has answered but I'm getting a "System.NullReferenceException: Object reference not set to an instance of an object." I've simplified the code as follows:

Event handler for the button click:

protected void btnSubmit_Click(object sender, EventArgs e)
{
    ViewState["MyKey"] = "Test";
}

The Page_Load now has:

protected void Page_Load(object sender, EventArgs e)
{
    if (IsPostBack)
    {
        txtDisplay.Text = ViewState["MyKey"].ToString();
    }
}

My question is: Why is ViewState["MyKey"] coming back as null and causing a NullReference exception?

Please note that the code above is only a simplified version of what I'm trying to do. Please see the previous question given in the first line of this question to see full details.

Any suggestions?

Upvotes: 0

Views: 170

Answers (2)

aleafonso
aleafonso

Reputation: 2256

The NullReferenceException might be related to the fact that you are trying to get the ViewState["MyKey"] value before you have set it. Try validating first:

if (ViewState["MyKey"] != null)
{
    txtDisplay.Text = ViewState["MyKey"].ToString();
}
else
{
    //manage the situation accordingly
}

Hope this helps!

Upvotes: 0

iandayman
iandayman

Reputation: 4467

Because in the asp page lifecycle the page load is called before the postback event is executed.

How about: -

protected void btnSubmit_Click(object sender, EventArgs e)
{
    txtDisplay.Text = "Test";
}

Upvotes: 1

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