//窗体关闭事件
private void Form_EnterDataSource_FormClosing(object sender, FormClosingEventArgs e)
{
_instance = null;
}
//创建窗体对象的静态方法
public static Form_EnterDataSource InstanceObject()
{
if (_instance == null)
_instance = new Form_EnterDataSource();
return _instance;
}
