Dynamically added controls in Asp.Net

Question

I\'m trying to wrap my head around asp.net. I have a background as a long time php developer, but I\'m now facing the task of learning asp.net and I\'m having some trouble w

Answer 1

I agree with the other points made here "If you can get out of creating controls dynamically, then do so..." (by @Jesper Blad Jenson aka) but here is a trick I worked out with dynamically created controls in the past.

The problem becomes chicken and the egg. You need your ViewState to create the control tree and you need your control tree created to get at your ViewState. Well, that's almost correct. There is a way to get at your ViewState values just before the rest of the tree is populated. That is by overriding LoadViewState(...) and SaveViewState(...).

In SaveViewState store the control you wish to create:

protected override object SaveViewState()
{
    object[] myState = new object[2];
    myState[0] = base.SaveViewState();
    myState[1] = controlPickerDropDown.SelectedValue;

    return myState
}

When the framework calls your "LoadViewState" override you'll get back the exact object you returned from "SaveViewState":

protected override void LoadViewState(object savedState) 
{
    object[] myState = (object[])savedState;

    // Here is the trick, use the value you saved here to create your control tree.
    CreateControlBasedOnDropDownValue(myState[1]);

    // Call the base method to ensure everything works correctly.
    base.LoadViewState(myState[0]);
}

I've used this successfully to create ASP.Net pages where a DataSet was serialised to the ViewState to store changes to an entire grid of data allowing the user to make multiple edits with PostBacks and finally commit all their changes in a single "Save" operation.

Answer 2

Ah, that's the problem with the leaky abstraction of ASP.NET web forms.

Maybe you'll be interested to look at ASP.NET MVC, which was used for the creation of this stackoverflow.com web site? That should be an easier fit for you, coming from a PHP (thus, pedal-to-the-metal when it comes to HTML and Javascript) background.

Answer 3

I think the answer here is in the MultiView control, so that for example the dropdown switches between different views in the multi-view.

You can probably even data-bind the current view property of the multiview to the value of the dropdown!