c# - 使用 PostAsJsonAsync 调用 Web API

Question

我是一个尝试调用 web api 方法的新手。

我有一个四边形对象:

public class Quadrilateral
{
    public double SideA { get; private set; }
    public double SideB { get; private set; }
    public double SideC { get; private set; }
    public double SideD { get; private set; }

    public double AngleAB { get; private set; }
    public double AngleBC { get; private set; }
    public double AngleCD { get; private set; }
    public double AngleDA { get; private set; }

    public virtual string Name { get { return "Generic Quadrilateral"; } }
    public virtual string Description { get { return "A quadrilateral that has no specific name for its shape"; } }

    public Quadrilateral(double sideA, double sideB, double sideC, double sideD,
                        double angleAB, double angleBC, double angleCD, double angleDA)
    {
        SideA = sideA;
        SideB = sideB;
        SideC = sideC;
        SideD = sideD;
        AngleAB = angleAB;
        AngleBC = angleBC;
        AngleCD = angleCD;
        AngleDA = angleDA;
    }

}

我的 web api post 方法做的事情非常简单。它接受一个 Quadrilateral 对象，并返回一个 Quadrilateral 的子类型，一个矩形:

public class Rectangle : Quadrilateral
{
    public override string Name { get { return "Rectangle"; } }

    public override string Description { get { return "A quadrilateral with equal opposite sides and 4 right angles"; } }

    public Rectangle(Quadrilateral q) :
        base(q.SideA, q.SideB, q.SideC, q.SideD,
            q.AngleAB, q.AngleBC, q.AngleCD, q.AngleDA) { }

}

web api post 方法如下所示:

public Quadrilateral Post(Quadrilateral q)
{
    return new Rectangle(q); 
}

我创建一个四边形对象，为成员分配值。然后我尝试使用以下代码调用我的 web api:

readonly string baseUri = "http://localhost:43798/";
readonly string controller = "api/quadrilateral";

using (HttpClient client = new HttpClient())
{
    client.BaseAddress = new Uri(baseUri);
    client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
    HttpResponseMessage response = await client.PostAsJsonAsync(controller, quadrilateral);

    if (response.IsSuccessStatusCode)
    {
        return await response.Content.ReadAsAsync<Quadrilateral>();
    }
    else
    {
        return null;
    }
}

调试显示 web api post 方法被命中，但 Quadrilateral 对象现在只包含 0.0 的所有 double 成员。为什么 post 方法没有得到我要发送的对象？

Answer 1

我假设您的问题现在已经解决，但这可能是因为您在 post 方法中省略了 [FromBody] 属性。你可以尝试:

public Quadrilateral Post([FromBody] Quadrilateral q)
{
    return new Rectangle(q); 
}