自定義ASP.NET CreateUserWizard中DropDownList的問題

Question

我在Web應用程序中使用了自定義的ASP.NET CreateUserWizard 。

在這里，我使用dropdownlist填充了用戶注冊時的國家/地區。 在page load ，按預期填充國家/地區。

var query = GetNationality();
var national = (DropDownList)RegisterUser.CreateUserStep.ContentTemplateContainer.FindControl("Nationality");
national.DataSource = query;
national.DataTextField = "CountryName";
national.DataValueField = "Id";
national.DataBind();

var item = new ListItem("Select Country", "");
national.Items.Insert(0, item);

但是當我嘗試從OnCreatedUser事件中的dropdownlist獲取值時，它產生了一條錯誤消息

System.FormatException：輸入字符串的格式不正確

我在做的是OnCreatedUser是

var national = (DropDownList)RegisterUser.CreateUserStep.ContentTemplateContainer.FindControl("Nationality");

var nationality = Convert.ToInt32(national.SelectedValue); <<-(where the error is)

該頁面的完整代碼如下

protected void Page_Load(object sender, EventArgs e)
{
        if (!IsPostBack)
        {
            FillDropdown();
        }

    }
    protected void RegisterUser_CreatedUser(object sender, EventArgs e)
    {
        var newUser = Membership.GetUser(RegisterUser.UserName);
        var newUserId = (Guid)newUser.ProviderUserKey;

        var name1 = (TextBox)RegisterUser.CreateUserStep.ContentTemplateContainer.FindControl("fname");
        var name2 = (TextBox)RegisterUser.CreateUserStep.ContentTemplateContainer.FindControl("lname");
        var comp = (TextBox)RegisterUser.CreateUserStep.ContentTemplateContainer.FindControl("Company");
        var post = (TextBox)RegisterUser.CreateUserStep.ContentTemplateContainer.FindControl("Position");
        var birth = (TextBox)RegisterUser.CreateUserStep.ContentTemplateContainer.FindControl("Bday");
        var mob = (TextBox)RegisterUser.CreateUserStep.ContentTemplateContainer.FindControl("Mobile");
        var aphone = (TextBox)RegisterUser.CreateUserStep.ContentTemplateContainer.FindControl("altPhone");
        var aemail = (TextBox)RegisterUser.CreateUserStep.ContentTemplateContainer.FindControl("altEmail");
        var national = (DropDownList)RegisterUser.CreateUserStep.ContentTemplateContainer.FindControl("Nationality");      
        var news = (CheckBox)RegisterUser.CreateUserStep.ContentTemplateContainer.FindControl("Newsletter");

        var title = tit.Text.Trim();        
        var nationality = national.Text;
        var preferred = method.Text.Trim();
        var newsleter = news.Checked;


        FormsAuthentication.SetAuthCookie(RegisterUser.UserName, false /* createPersistentCookie */);

        var continueUrl = RegisterUser.ContinueDestinationPageUrl;
        if (String.IsNullOrEmpty(continueUrl))
        {
            continueUrl = "~/";
        }
        Response.Redirect(continueUrl);
    }

    public void FillDropdown()
    {
        var query = GetNationality();
        var national = (DropDownList)RegisterUser.CreateUserStep.ContentTemplateContainer.FindControl("Nationality");
        national.DataSource = query;
        national.DataTextField = "CountryName";
        national.DataValueField = "Id";
        national.DataBind();
        var item = new ListItem("Select Country", "");
        national.Items.Insert(0, item);
    }

}

任何想法將不勝感激。 謝謝

Answer 1

能否將填充DropDownList的代碼放在!IsPostBack下的Page_Load方法中？

protected void Page_Load(object sender, EventArgs e)
{
    if(!IsPostBack)
    {
        var query = GetNationality();
        var national = (DropDownList)RegisterUser.CreateUserStep.ContentTemplateContainer.FindControl("Nationality");
        national.DataSource = query;
        national.DataTextField = "CountryName";
        national.DataValueField = "Id";
        national.DataBind();

        var item = new ListItem("Select Country", "");
        national.Items.Insert(0, item);
    }
}

可能是當您回發時，您的DropDownList受到重新綁定，因此您始終會獲得第一項，並且嘗試將空字符串轉換為會給您錯誤消息的int。