Question

 public Form1()
    {
        InitializeComponent();
    }

    private void checkBox1_CheckedChanged(object sender, EventArgs e)
    {
        textBox1.Enabled = checkBox1.Checked;
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        checkBox1.Checked = false;
    }

I set the check state in load event handler, and why in this case, the CheckedChanged not fired?
If i click the check box, then the CheckedChanged is fired.

Answer 1

If your checked state is initially false, then setting it to false again doesn’t fire the CheckedChanged event.
That happens because the checked state isn’t actually changed

This is the internal code used when trying to set the CheckBox1.Checked property

public void set_Checked(bool value)
{
    if (value != this.Checked)
    {
        this.CheckState = value ? CheckState.Checked : CheckState.Unchecked;
    }
}