Dynamically created controls causing Null reference

Question

I am trying to dynamically create controls and give them properties during run time.

I have put my code inside the Page_Init event, when I run my website I can see m

Answer 1

try to put your code in the Page_Load instead of Page_Init and also, check for null before using objects returned by FindControl.

I suspect the object InputTextBox is null and it crashes when you try to print its Text.

as a general rule just check for null and also for type when casting results of FindControl to something else.

Answer 2

I suggest that you declare your controls outside the page_int and do your initialization in the init then use them with their name instead of find control.

Answer 3

As FindControl is not recursive, you have to replace this code :

Label FeedbackLabel = (Label)FindControl("FeedbackLabel");
TextBox InputTextBox = (TextBox)FindControl("InputTextBox");

by this code :

Label FeedbackLabel = (Label)Panel1.FindControl("FeedbackLabel");
TextBox InputTextBox = (TextBox)Panel1.FindControl("InputTextBox");

However, according other answers, you should move the declaration (not the instantiation) outside the method (at class level) in order to easily get an entry for your controls.

Answer 4

    protected override void OnLoad(EventArgs e)
    {
        base.OnLoad(e);
        //-- Create your controls here
    }

Answer 5

The FindControl is failing because it can't find the control and causing a null reference.

Just reference it directly using FeedbackLabel as you already have it in your class. Just move the scope outside of your 'Init' method.

private Label feedbackLabel = new Label();
private TextBox inputTextBox = new TextBox();
private Button submitButton = new Button();

public void Page_Init(EventArgs e)
{
    feedbackLabel.ID = "FeedbackLabel";
}

protected void SubmitButton_Click(object sender, EventArgs e)
{
    feedbackLabel.Text =...;
}