使用PostAsJsonAsync調用Web API

Question

我是一個試圖調用web api方法的新手。

我有一個Quadrilateral對象：

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方法做的很簡單。 它接受一個Quadrilateral對象，並返回一個Quadrilateral的子類型，一個矩形：

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); 
}

我創建一個Quadrilateral對象，分配成員值。 然后我嘗試使用以下代碼調用我的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;
    }
}

調試顯示web api post方法被命中，但Quadrilateral對象現在只包含其所有double成員的0.0。 為什么post方法沒有得到我試圖發送它的對象？

Answer 1

我假設您的問題現在已經解決，但可能是因為您在post方法中省略了[FromBody]屬性。 你本可以嘗試：

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

Answer 2

你發布的json值是多少？ 你確定在發布之前得到了正確的json嗎？

嘗試清除接受標頭，

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