C#-保存配置文件ASP.NET给定'；未设置对象引用'；错误

当我试图保存配置文件时，我得到的对象引用没有设置为对象错误的实例。

我试着添加一个"if"陈述if（this.Profile.ProfileDetails！=null）但它仍然给了我同样的错误。

这是我的代码：

private void SaveProfile()
    {

            this.Profile.ProfileDetail.FullName = txtfname.Text;
            this.Profile.ProfileDetail.IdentityCardNo = txtcardno.Text;
            this.Profile.ProfileDetail.IdentityCardColour = ddlcardcolor.SelectedValue;
            this.Profile.ProfileDetail.IdentityCardExpiryDate = DateTime.Parse(txtcardexp.Text);
            this.Profile.ProfileDetail.Race = ddlrace.SelectedValue;
            this.Profile.ProfileDetail.Religion = ddlreligion.SelectedValue;
            this.Profile.ProfileDetail.ContactInformation.Address1 = txtaddress1.Text;
            this.Profile.ProfileDetail.ContactInformation.Address2 = txtaddress2.Text;
            this.Profile.ProfileDetail.ContactInformation.Address3 = txtaddress3.Text;
            this.Profile.ProfileDetail.ContactInformation.Postcode = txtpostcode.Text;
            this.Profile.ProfileDetail.ContactInformation.District = ddldistrict.SelectedValue;
            this.Profile.ProfileDetail.ContactInformation.OfficePhone = txtphoneoffice.Text;
            this.Profile.ProfileDetail.ContactInformation.HomePhone = txtphonehome.Text;
            this.Profile.ProfileDetail.ContactInformation.MobilePhone = txtphonecell.Text;
            this.Profile.ProfileDetail.ContactInformation.Email = txtemail.Text;


        //this.Profile.ProfileDetail.FirstName = txtFirstName.Text;
        //this.Profile.ProfileDetail.LastName = txtLastName.Text;
        //this.Profile.ProfileDetail.IdentityCardNo = txtICNo.Text;
        //this.Profile.ProfileDetail.DateOfBirth = DateTime.Parse(txtDateOfBirth.Text);
        //this.Profile.ProfileDetail.Gender = (Gender)Enum.Parse(typeof(Gender), ddlGender.SelectedValue, true);
        //this.Profile.Preferences.TimeZone = ddlTimeZones.SelectedValue;
        //this.Profile.Preferences.Culture = ddlCultures.SelectedValue;
        this.Profile.Save();
        this.ResetElements();
    }