如何在C＃中更改我的一个文本框时启用按钮？

Question

Today I got a problem in my development.

I have a Windows Form like this :

I need to enable the button "Appliquer" when the content of one of my textbox change. I know that I can put the KeyPress event on each textbox and enable my button with that. In this window it can be easy to do that because there is only 10 textbox but I have an other window with more of 100 textbox and I think there is a better solution.

I tried to put the Keydown event directly in my windows form but it doesn't work. So my question is, how can I do this. If someone have an idea ?

Thank you in advance !

Thomas

Answer 1

Since you already have 100+ textboxes in your form. I am assuming performance is not an issue for you.

In your form constructor, call this method. It will attach the event to all the textbox controls present in your form & inside sub controls such as groupbox, panel etc. (if you require)

There could be better ways of iteration..

public Form1()//your constructor
        {
            InitializeComponent();

            AttachEvent(this);

        }
     void AttachEvent(Control CTrl)
            {
                foreach (Control c in CTrl.Controls)
                {
                    if (c is TextBox)
                    {
                        c.TextChanged += new EventHandler(c_TextChanged);
                        continue;
                    }
                    if (c.HasChildren)
                    {
                        AttachEvent(c);
                    }
                }
            }

            void c_TextChanged(object sender, EventArgs e)
            {
                //Your Code here btnGo.Enabled = !btnGo.Enabled;
            }

Answer 2

What you can do is to extend TextBox make a field ( accessible from the designer ) to bind that TextBox into some other control.

public class MeTextBox
    : TextBox
{
    public override string Text
    {
        get { return base.Text; }
        set
        {
            if ( m_DependantControl != null )
            {
                m_DependantControl.Enabled = !string.IsNullOrWhiteSpace(value);
            }
            base.Text = value;
        }
    }

    Control m_DependantControl;

    [Browsable(true)]
    public Control DependantControl
    {
        get { return m_DependantControl; }
        set { m_DependantControl = value; }
    }
}

Now you can use MeTextBox as a regular TextBox . And if you want to make it control Enabled flag of some other Control you can just specify DependantControl property which will be accessible in the designer.

Fitting this into your example ( code ):

// assume you have a Button named btnConfirm
// and want to enable this button only when your `TextBox` has some text
MeTextBox mtb = new MeTextBox();
mtb.DependantControl = btnConfirm;

And if you do not want to make it in the code you can use designer directly.

To make it other way around ( one button dependant on many text boxes ) you can extend Button object :

public class MeButton
    : Button
{
    List<TextBox> m_DependantOn = new List<Control>();

    [Browsable(true)]
    public List<TextBox> DependantOn
    {
        get { return m_DependantOn; }
        set { RemoveEvents(); m_DependantOn = value; AssignEvents(); }
    }

    void RemoveEvents()
    {
        foreach(TextBox ctrl in m_DependantOn)
            ctrl.TextChanged -= WhenTextChanged;
    }

    void AssignEvents()
    {
        foreach(TextBox.ctrl in m_DependantOn)
            ctrl.TextChanged += WhenTextChanged;
    }

    void WhenTextChanged(object sender, TextChangedEventArgs e)
    {
        this.Enabled = true;
    }
}