c# - 错误对象引用未设置为对象的实例？

Question

我已经通过我的代码查看是否存在任何空值，但每个人都带来了价值，但我找不到问题。

public partial class UserDetail : ICSBaseUserControl
{
    UserRepository userDao = new UserRepository();
    User user;
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            long userID = Convert.ToInt64(Request[UrlParameters.UrlParameterName.UserID]);
            user = (userID > 0) ? userDao.GetUser(AppSession.Company.ID, userID) : new c365_EntityFramework.User();
            if (user.ID > 0)
            {
                txtFirstName.Text = user.Forename;
                txtSurname.Text = user.Surname;
                txtAddress.Text = user.Address1;
                txtEmail.Text = user.Email;
                txtUsername.Text = user.Username;

            }
        }
    }

    protected void Button2_Click(object sender, EventArgs e)
    {
        bool result = userDao.UpdateUser(user.ID, txtFirstName.Text, txtEmail.Text, txtSurname.Text, txtAddress.Text, txtUsername.Text);
    }
}

编辑

这就是我修复它的方法，将user加载移出if(!IsPostBack)：

public partial class UserDetail : ICSBaseUserControl
{
    UserRepository userDao = new UserRepository();
    User user;
    protected void Page_Load(object sender, EventArgs e)
    {
        long userID = Convert.ToInt64(Request[UrlParameters.UrlParameterName.UserID]);
        user = (userID > 0) ? userDao.GetUser(AppSession.Company.ID, userID) : new c365_EntityFramework.User();
        if (!IsPostBack)
        {
            if (user.ID > 0) // Check for user ID
            {
                txtFirstName.Text = user.Forename;
                txtSurname.Text = user.Surname;
                txtAddress.Text = user.Address1;
                txtEmail.Text = user.Email;
                txtUsername.Text = user.Username;
            }
        }
    }

Answer 1

我认为问题在于该字段user没有被实例化，因此将null在您的按钮单击上。

如果不是回发，您Page_Load唯一的填充。那么，当您按下按钮时，回发正在进行中，而您当时没有收到？此外，您需要查看 ASP .NET 页面生命周期。useruser

ASP .NET 页面不记得字段，您可能希望将其user置于会话状态，然后以这种方式使用它。