C#: Dynamic user Control IsPostback returning true event though the UC is loaded the first time

Question

I have a Page with a Dynamic User Control in a placeholder. When I load the Page it loads a UC ( let's call it "OrigUC" ) by default. On this page I have a button , which replaced the UC with another "NewUC" . So this button postback using ajax and replaces the UC .

In the NewUC, In my Page_Load, I check for IsPostBack(), but for some reason, even though I loaded the UC for the first time it still returns me true. Why is it returning true, I thought the IsPostBack will return whether the UC since I'm checking it inside the Page_Load of the UC .Am I missing something?

Ok I now understand more the IsPostback on a user control coming from the Page it is called from... So how can I determine if it is the first time the UC is being called from the page?

Example:

If it is the first time the UC is called within the page, I need to querythe DB and also external WebS and bind the controls on the UC. If I trigger a partial postback , I do not want to query the DB and WebS again.

If (!IsUserControlPostBack) 
{ 
// Step 1 Init of UC 
// Call to DB 
// Call to WebS 
} 
else 
{ 
// A Post back occured ...  
// It can be Page who triggered it or UC and I do not want to call Step 1 again 
// DO something else. 
}

C

Define "first time". First time in your application? First time for this user? First time on this full page refresh (i.e. via ajax). What is first time in a web environment? — Stilgar, Mar 14 '12 at 14:33

score 2 · Answer 1 · answered Mar 14 '12 at 12:09

The IsPostBack property determines if the request was a POST HTTP request not if your control did anything. Because the page was submitted via a button the request is a PostBack request (in ASP.NET terms). Basically this property does not do what you think it does and in fact is not related in any way.

score 2 · Accepted Answer · answered Mar 16 '12 at 09:57

Ok I've used ViewState to store the flag that I set when loading the User Control the first time I go in.

Hope this help another noob like me :)

    private bool IsUCPostBack
    {
        get
        {
            object o = ViewState["S2UC"];
            return o == null;
        }
        set
        {
            ViewState["S2UC"] = true;
        }
    }

    protected void Page_Load(object sender, EventArgs e)
    {
        if (IsUCPostBack)
        {
            IsUCPostBack = true; ... } else { ...   }

The ispostback property in user control fails. This is a better way to check if the control is loaded for the first time. Thanks for sharing. — Sugar Bowl, Nov 10 '14 at 20:06

score 1 · Answer 3 · answered Mar 14 '12 at 12:10

1

The button is performing a "postback". IsPostBack is true for the Page object in which the user control is being loaded.

answered Mar 14 '12 at 12:10

Chris Gessler

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Ok I now understand more the IsPostback on a user control coming from the Page it is called from... So how can I determine if it is the first time the UC is being called? – Gotcha Mar 14 '12 at 14:30
I'm afraid there's no built-in way to tell, but you could set a session variable using the control name and set the value to true. If it exists, the control has already been loaded, else, it hasn't. – Chris Gessler Mar 14 '12 at 19:33

C#: Dynamic user Control IsPostback returning true event though the UC is loaded the first time

3 Answers3