Blazor 应用程序找不到嵌套模型

Question

我有这个 Blazor 应用程序，其中有以下模型类：

    public class Purchase
{
    public Payment payment { get; set; }
}

public class Payment
{
    public string operation { get; set; }
    public string intent { get; set; }
    public string currency { get; set; }
    public Price[] prices { get; set; }
    public string description { get; set; }
    public string userAgent { get; set; }
    public string language { get; set; }
    public Urls urls { get; set; }
    public Payeeinfo payeeInfo { get; set; }
    public Cardholder cardholder { get; set; }
    public Riskindicator riskIndicator { get; set; }
}

public class Urls
{
    public string completeUrl { get; set; }
    public string cancelUrl { get; set; }
    public string callbackUrl { get; set; }
    public string logoUrl { get; set; }
    public string termsOfServiceUrl { get; set; }
}

public class Payeeinfo
{
    public string payeeId { get; set; }
    public string payeeReference { get; set; }
    public string payeeName { get; set; }
    public string productCategory { get; set; }
    public string orderReference { get; set; }
    public string subsite { get; set; }
}

public class Cardholder
{
    public string firstName { get; set; }
    public string lastName { get; set; }
    public string email { get; set; }
    public string msisdn { get; set; }
    public string homePhoneNumber { get; set; }
    public string workPhoneNumber { get; set; }
    public Shippingaddress shippingAddress { get; set; }
}

public class Shippingaddress
{
    public string firstName { get; set; }
    public string lastName { get; set; }
    public string email { get; set; }
    public string msisdn { get; set; }
    public string streetAddress { get; set; }
    public string coAddress { get; set; }
    public string city { get; set; }
    public string zipCode { get; set; }
    public string countryCode { get; set; }
}

public class Riskindicator
{
    public string deliveryEmailAddress { get; set; }
    public string deliveryTimeFrameIndicator { get; set; }
    public string preOrderDate { get; set; }
    public string preOrderPurchaseIndicator { get; set; }
    public string shipIndicator { get; set; }
    public bool giftCardPurchase { get; set; }
    public string reOrderPurchaseIndicator { get; set; }
    public Pickupaddress pickUpAddress { get; set; }
}

public class Pickupaddress
{
    public string name { get; set; }
    public string streetAddress { get; set; }
    public string coAddress { get; set; }
    public string city { get; set; }
    public string zipCode { get; set; }
    public string countryCode { get; set; }
}

public class Price
{
    public string type { get; set; }
    public int amount { get; set; }
    public int vatAmount { get; set; }
}

我尝试在 razor 组件中这样实现：

@page "/testpay"
@using Kanal10.UI.Models.Payex

<!-- Content -->
<div class="donate">
    <div class="donate-pay wrapper">
        <EditForm Model="purchase" OnValidSubmit="SavePurchase">
            <div class="row">
                <div class="col-md-6 col-sm-12">
                    <div class="form-group">
                        <label>Firstname</label>
                        <InputText id="firstName" @bind-value="purchase.payment.cardholder.firstName" class="form-control"></InputText>
                    </div>
                </div>

            </div>
            <button type="submit" class="btn btn-primary">Save</button>
        </EditForm>


    </div>
</div>
@code {
    private Purchase purchase = new Purchase();

    private void SavePurchase()
    {

    }
}

但是当我渲染页面时，我收到错误消息，我不太明白为什么。

NullReferenceException：对象引用未设置为对象的实例。 Kanal10.UI.Pages.PayTest.b__0_1(RenderTreeBuilder __builder2)

如果有人有答案，我将不胜感激。

彼得

Answer 1

为了做这样的事情：

<InputText id="firstName" @bind-value="purchase.payment.cardholder.firstName" class="form-control"></InputText>

你必须这样做：

@code
{
    private Purchase purchase = new Purchase { payment=new Payment() 
                                    {cardholder=new Cardholder(){}}};
}

如果我没有错过链中的某些内容，这应该可以工作。但是原则很清楚：您必须实例化一个嵌入在父对象实例中的对象，该对象本身嵌入在祖父对象的实例中，依此类推。这与 Blazor 无关。这是 C#。您必须先实例化一个对象才能使用它，不是吗？

注意：字段的名称，例如payment in

public Payment payment { get; set; }

不仅可以命名为Payment，而且按照惯例我们是这样定义的（尤其是以大写字母开头）。所以让它public Payment Payment{ get; set; }

Answer 2

试试嵌套对象验证器https://docs.microsoft.com/en-us/aspnet/core/blazor/forms-validation?view=aspnetcore-5.0#nested-models-collection-types-and-complex-types

另外，尝试初始化您的嵌套模型，使其不为空