Windows Form窗体的关闭按钮的启用与否

public partial class Form1 : Form
{
private bool isEnableCloseButton = false;
public Form1(string strFlag)
{
InitializeComponent();
if (strFlag == "no")
{
this.lbl_CloseButtonIsEnabled.Text = "窗体右上角关闭按钮无效";
this.isEnableCloseButton = false;
}
else
{
this.lbl_CloseButtonIsEnabled.Text = "可以通过窗体右上角关闭按钮 关闭窗体";
this.isEnableCloseButton = true;
}
}

protected override CreateParams CreateParams
{
get
{
if (isEnableCloseButton)
{
CreateParams parameters = base.CreateParams;
return parameters;
}
else
{
int CS_NOCLOSE = 0x200;
CreateParams parameters = base.CreateParams;
parameters.ClassStyle |= CS_NOCLOSE;
return parameters;
}
}
}
}

//调用显示该窗体
Form1 frm = new Form1("no");
frm.ShowDialog();