使用 C# asp.net 更新 Web 应用中的用户信息

我正在创建一个Web应用程序，在此应用程序中，我希望允许用户更新其用户信息（名字，姓氏，电子邮件，电话号码，公司名称）或更改密码。 当页面加载时，其当前信息将输入到文本框中。 我的问题是我不知道如何应用用户所做的更改。 我的代码目前如下所示：

    DataClasses1DataContext context = new DataClasses1DataContext();
    User user = new User();

    protected void Page_Load(object sender, EventArgs e)
    {
        string usr = Session["SessionUserName"].ToString();
        user = (from u in context.Users
                    where u.username.Equals(usr)
                    select u).FirstOrDefault();
        txtFName.Text = user.firstName;
        txtLName.Text = user.lastName;
        txtCompany.Text = user.companyName;
        txtEmail.Text = user.email;
        txtPhone.Text = user.phoneNumber;

    }
    protected void btnUpdate_Click(object sender, EventArgs e)
    {
        using (DataClasses1DataContext context2 = new DataClasses1DataContext())
        {
            User nUser = (from u in context2.Users
                          where u.username == user.username
                          select u).SingleOrDefault();
            if (nUser != null)
            {
                //make the changes to the user
                nUser.firstName = txtFName.Text;
                nUser.lastName = txtLName.Text;
                nUser.email = txtEmail.Text;
                if (!String.IsNullOrEmpty(txtPhone.Text))
                    nUser.phoneNumber = txtPhone.Text;
                if (!String.IsNullOrEmpty(txtCompany.Text))
                    nUser.companyName = txtCompany.Text;
                nUser.timeStamp = DateTime.Now;
            }

            //submit the changes
            context2.SubmitChanges();
            Response.Redirect("Projects.aspx");
        }

这不会给我任何错误，但它也不会应用更改。 一些谷歌搜索导致我添加

context2.Users.Attach(nUser);

但这给了我错误消息：System.InvalidOperationException：无法附加已经存在的实体。 所以我尝试了

context2.Users.Attach(nUser, true); 

我收到了相同的错误消息。

再看谷歌，我发现了有关首先分离实体的信息，但该信息大约有 3 年的历史，似乎不再有效（作为上下文。分离或上下文。Users.Detach 不是选项，如果我尝试使用它们，会给我构建错误）。 我收到的其他错误消息（我不记得我是如何诚实地到达的）建议我更改更新策略，以便我将 Users 类下的所有字段设置为从不更新策略。 有人建议反序列化然后再次序列化数据，但我找不到有关如何执行此操作的任何信息。 任何帮助将不胜感激。

编辑：由于下面的一些建议，更改了代码，但它仍然不起作用。 我没有收到任何错误消息，但数据未保存。

 protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            string usr = Session["SessionUserName"].ToString();
            user = (from u in context.Users
                    where u.username.Equals(usr)
                    select u).FirstOrDefault();
            txtFName.Text = user.firstName;
            txtLName.Text = user.lastName;
            txtCompany.Text = user.companyName;
            txtEmail.Text = user.email;
            txtPhone.Text = user.phoneNumber;
        }  
    }
    protected void btnUpdate_Click(object sender, EventArgs e)
    {

                //make the changes to the user
                user.firstName = txtFName.Text;
                user.lastName = txtLName.Text;
                user.email = txtEmail.Text;
                if (!String.IsNullOrEmpty(txtPhone.Text))
                    user.phoneNumber = txtPhone.Text;
                if (!String.IsNullOrEmpty(txtCompany.Text))
                    user.companyName = txtCompany.Text;
                user.timeStamp = DateTime.Now;
                //submit the changes
            context.SubmitChanges();
            Response.Redirect("Projects.aspx");
      }

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        string usr = Session["SessionUserName"].ToString();
        user = (from u in context.Users
                where u.username.Equals(usr)
                select u).FirstOrDefault();
        txtFName.Text = user.firstName;
        txtLName.Text = user.lastName;
        txtCompany.Text = user.companyName;
        txtEmail.Text = user.email;
        txtPhone.Text = user.phoneNumber;
    }
}

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        if (Session["SessionUserName"] != null)
        {
            string usr = Session["SessionUserName"].ToString();
            DataClasses1DataContext context = new DataClasses1DataContext();
            User user = (from u in context.Users
                         where u.username.Equals(usr)
                         select u).FirstOrDefault();
            if (user != null)
            {
                txtFName.Text = user.firstName;
                txtLName.Text = user.lastName;
                txtCompany.Text = user.companyName;
                txtEmail.Text = user.email;
                txtPhone.Text = user.phoneNumber;
            }
            else
            {
                //--- handle user not found error
            }
        }
        else
        {
            //--- handle session is null
        }
    }
}
protected void btnUpdate_Click(object sender, EventArgs e)
{
    if (Session["SessionUserName"] != null)
    {
        string usr = Session["SessionUserName"].ToString();
        try
        {
            DataClasses1DataContext context = new DataClasses1DataContext();
            User nUser = (from u in context.Users
                          where u.username.Equals(usr)
                          select u).FirstOrDefault();
            //make the changes to the user
            nUser.firstName = txtFName.Text;
            nUser.lastName = txtLName.Text;
            nUser.email = txtEmail.Text;
            if (!String.IsNullOrEmpty(txtPhone.Text))
                nUser.phoneNumber = txtPhone.Text;
            if (!String.IsNullOrEmpty(txtCompany.Text))
                nUser.companyName = txtCompany.Text;
            nUser.timeStamp = DateTime.Now;
            //submit the changes
            context.SubmitChanges();
            Response.Redirect("Projects.aspx");
        }
        catch (Exception ex)
        {
            //--- handle update error
        }
    }
    else
    {
        //--- handle null session error
    }
}