[英]Type is an interface or abstract class and cannot be instantiated. c# send a object with contain a list of abstract object
[英]ReadAsAsync - Error : “Type is an interface or abstract class and cannot be instantiated.”
我有以下代碼從web api服務獲取對象。
在以下代碼行
response.Content.ReadAsAsync<CMLandingPage>().Result;
我得到以下異常:
InnerException = {"Could not create an instance of type MLSReports.Models.IMetaData. Type is an interface or abstract class and cannot be instantiated. Path 'BaBrInfo.Series[0].name', line 1, position 262."}
任何指針都非常感謝。
CMLandingPage lpInfo = new CMLandingPage();
try
{
using (HttpClient client = new HttpClient())
{
// Add an Accept header for JSON format
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
response = client.PostAsJsonAsync(LPChartinfoapiURL, criteria.Mlsnums).Result;
}
// Throw exception if not a success code.
response.EnsureSuccessStatusCode();
// Parse the response body.
lpInfo = response.Content.ReadAsAsync<CMLandingPage>().Result;
}
CMLandingPage:
namespace MLSReports.Models
{
public class CMLandingPage
{
public CMLandingPage() { }
public CMColumn BaBrInfo { get; set; }
}
public class CMColumnItem<T> : IMetaData
{
#region Constructors and Methods
public CMColumnItem() { }
#endregion
#region Properties and Fields
public string name { get; set; }
public List<T> data { get; set; }
public string color { get; set; }
#endregion
}
public class CMColumn
{
#region Constructor and Method
public CMColumn()
{
Series = new List<IMetaData>();
}
#endregion
#region Properties and Fields
public string ChartType { get; set; }
public string ChartTitle { get; set; }
public List<IMetaData> Series { get; set; }
#endregion
}
}
您的CmColumn
類上有此屬性:
public List<IMetaData> Series { get; set; }
WebApi控制器顯然試圖根據您發送它的參數值構造一個對象。 當它到達名為“BaBrInfo.Series [0] .name”的值時,它知道它應該創建一個新的IMetaData
對象,以便它可以設置它的name
並將其添加到Series
屬性,但IMetaData
只是一個接口:它不知道要構造什么類型的對象。
嘗試將IMetaData
更改為實現該接口的某種具體類型。
您需要讓序列化程序在json有效負載和反序列化器中包含類型以使用包含的類型:
//Serialization
var config = new HttpConfiguration();
config.Formatters.JsonFormatter.SerializerSettings.TypeNameHandling = TypeNameHandling.Auto;
return Request.CreateResponse(HttpStatusCode.OK, dto, config);
//Deserialization
var formatter = new JsonMediaTypeFormatter
{
SerializerSettings = { TypeNameHandling = TypeNameHandling.Auto }
};
response.Content.ReadAsAsync<CMLandingPage>(new [] { formatter }).Result;
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