C# WinForm 창 닫기(종료) 방지

private void mainFrm_FormClosing(object sender, FormClosingEventArgs e)
{
   // e.Cancel, true = 종료 취소, false = 종료 (default : false)
   e.Cancel = true;
}

/* 활용안 : 특정 버튼으로만 종료시키고자 할 때 */

public class mainFrm : Form
{
    bool _closeCancel = true;

    // ... 생략 ....

    private void btnClose_Click(object sender, EventArgs e)
    {
        _closeCancel = false;
        this.Close();
    }
    
    private void mainFrm_FormClosing(object sender, FormClosingEventArgs e)
    {
        // e.Cancel, true = 종료 취소, false = 종료 (default : false)
        e.Cancel = _closeCancel;
    }
}