通过验证表单中单击的按钮来跟踪Windows表单的关闭事件

Question

I have a form which contains a close button (there are many control in the form, but I am concerning about the close event) and a save button.

If a form have value in certain text box (say TextBox1),

Then I want to validate that the save button is clicked before closing the form (whether close button or the 'X' button at top is pressed).

But if there is no value in that text box or the form is just initialized and user just want to close the form, it simply closes the form. How to perform this validation.

Answer 1

I would follow the pattern of 99% of windows applications: allow to close a window, but ask to save changes if there are any. Here is a simple implementation of that pattern:

private bool _hasChanges;

private void textBox1_TextChanged(object sender, EventArgs e)
{
    this._hasChanges = true;
}

private void form_FormClosing(object sender, FormClosingEventArgs e)
{
    if (this._hasChanges)
    {
        var dialogResult = MessageBox.Show("Save changes?", "Confirm", MessageBoxButtons.YesNoCancel);
        switch (dialogResult)
        {
            case DialogResult.Yes:
                this.Save();
                break;
            case DialogResult.No:
                this._hasChanges = false;
                break;
        }
        e.Cancel = this._hasChanges;
    }
}

private void Save()
{
    // Save
    this._hasChanges = false;
}

private void buttonSave_Click(object sender, EventArgs e)
{
    this.Save();
}

private void buttonOk_Click(object sender, EventArgs e)
{
    this.Close();
}

private void buttonCancel_Click(object sender, EventArgs e)
{
    this._hasChanges = false;
    this.Close();
}

The pivotal part is the boolean _hasChanges . If there are many controls that can cause changes this can be real pain. An alternative could be to use databinding to a class that implements INotifyPropertyChanged and subscribe to its PropertyChanged event.

Answer 2

Tie into the Closing Event and use your EventHandler to validate that textbox. Keep in mind that Closing occurs at the time the form is closing and (if memory servers correctly) there is a property on the eventarg that will let you cancel closing of the form. This event is raised regardless of how the request is executed.