Question

An apply button on my standard winform is disabled on loading and I want to enable it, if a state of any other control changes (checkboxes, radioboxes, textboxes etc.)

So I could go through the events of every single control and enable the button there but I want to know if there is an easier way to do it, like a global event.

Edit
To clarify: I’m looking for a method where I havn’t to do something with every single control. So that I can add more controls at a later point and don’t have to care about them …

Answer 1

As per your edit I’ve revised my answer to include the functionality you desire.

First you need a generic event handler that should look something like this:

void MyHandler(object obj, EventArgs e)
{
    button1.Enabled = true;
}

Where button1 is the button you wish to enable.

Then you’re going to need a recursive method to not only iterate through your Form.Controls, but any container type controls contained in there as well. I’ve included handling of some common container controls as well as some basic data entry controls:

void AddEvents(System.Windows.Forms.Control.ControlCollection Controls)
{
    foreach (Control c in Controls)
    {
        if (c is GroupBox)
        {
            AddEvents(((GroupBox)c).Controls);
        }
        else if (c is Panel)
        {
            AddEvents(((Panel)c).Controls);
        }
        //Expand this series of if...else... to include any 
        //other type of container control
        else if (c is TextBox)
        {
            ((TextBox)c).TextChanged += new EventHandler(MyHandler);
        }
        else if (c is RichTextBox)
        {
            ((RichTextBox)c).TextChanged += new EventHandler(MyHandler);
        }
        else if (c is CheckBox)
        {
            ((CheckBox)c).CheckedChanged += new EventHandler(MyHandler);
        }
        else if (c is DateTimePicker)
        {
            ((DateTimePicker)c).ValueChanged += new EventHandler(MyHandler);
        }
        //Expand this to include any other type of controls your form 
        //has that you need to add the event to
    }
}

The first part of the if else block checks to see if the control is of a type that contains other controls. If it is it then recursively calls the AddEvents method with the new System.Windows.Forms.Control.ControlCollection contained in that control.

The second part of the if else block checks what type of control c is so that it can be appropriately cast to the correct type, and therefore utilize the correct event. If we are able to determine our control type at this point, the generic event created earlier is added as a handler.

Last, you need to call this method. The two best places would probably be either in your constructor or on the Form.Load event. The best place to put it will depend on your specific circumstances. I chose to use my constructor for simplicity, which now looks like this:

public Form1()
{
    InitializeComponent();
    AddEvents(this.Controls);
}

And that should be all you need to iterate your controls and add the generic event handler. This code is from an actual project I created and I have tested it to ensure it’s proper functionality.

EDIT: I’ve also just tested this using controls inside of a GroupBox inside of a Panel inside of a GroupBox inside of a Panel that’s on a Form. This is where the usefulness of utilizing recursion comes in. You don’t need to know to exact depth of nesting so long as you properly set up your if...else... blocks. It will go as deep as it needs to without needing to use nested loops and knowing the exact depth.

EDIT2: As a side note, this method could also be used on a more granular level. Let’s say you have multiple GroupBox controls and you wish to only add the event handler to controls in “grpBox1”. You could call AddEvents(grpBox1.Controls) instead of AddEvents(this.Controls) and this would only apply the event handler to controls contained in grpBox1.

EDIT3: As onemancat has pointed out in the comments, it’s not entirely necessary to actually check if the control is a GroupBox or a Panel etc. because all controls inherit from the base class Control which has a Controls property. You simply could check if the Control contains other controls by saying if (c.Controls.Count > 0) AddEvents(c.Controls); however, in a situation where one wants to choose which container controls to iterate, it would be necessary to check the type as I have in my example. If it’s not necessary to be this granular it does make more sense to check the count and never bother with type checking or casting.