[英]Empty JSON Response from Controller in C# Web API
I am learning about building web APIs in C#. 我正在学习如何在C#中构建Web API。
I am testing my controller, however I am getting an empty JSON
response. 我正在测试我的控制器,但是我得到了一个空的
JSON
响应。
This is my controller 这是我的控制器
public class ClassInfoController : ApiController
{
private ClassRepository classRepo = new ClassRepository();
public IList<string> getClassListByTerm(string termID)
{
List<string> classList = classRepo.getClassListByTerm(termID);
return classList;
}
This is my repository class which queries my Entity model 这是我的存储库类,它查询我的实体模型
public class ClassRepository : IClass
{
private cet_databaseEntities db = new cet_databaseEntities();
public List<string> getClassListByTerm(string termID)
{
List<string> result = (from t in db.classCodeLookup
where t.termID == termID
orderby t.@class ascending
select t.@class).ToList<string>();
return result;
}
}
I have debugged my controller and when the API call is made, this repository class returns no data to the controller ie an empty list
. 我已经调试了我的控制器,并且在进行API调用时,此存储库类不向控制器返回任何数据,即空
list
。 However, the reason I am confused, is that when I use the following test code on the repository class 但是,我感到困惑的原因是,当我在存储库类上使用以下测试代码时
public class ClassRepositoryTests
{
ClassRepository testRepo = new ClassRepository();
[TestMethod()]
public void getClassListByTermTest()
{
List<string> output = testRepo.getClassListByTerm("316a");
foreach (string className in output)
{
Console.WriteLine(className);
}
}
}
I get the result from the repository class I expect. 我从我期望的存储库类中获得结果。
Why am I having this issue? 我为什么遇到这个问题?
Try to add attribute to your API method 尝试向API方法添加属性
[HttpGet]
public List<string> getClassListByTerm([FromUri]string termID)
or you can use another class object for request data. 或者您可以使用另一个类对象来请求数据。 I mean
我的意思是
public class TermData
{
//use if nessassry [JsonProperty("TermId")]
public string TermId {get;set;}
}
[HttpGet]
public List<string> getClassListByTerm([FromUri]TermData data)
My issue was the automatic API documentation provided by a Web API project in Visual Studio told me that I should call my controller from the browser with the following: http://localhost:51520/api/ClassInfo?termID={316a}
. 我的问题是Visual Studio中的Web API项目提供的自动API文档告诉我,我应该使用以下命令从浏览器调用我的控制器:
http://localhost:51520/api/ClassInfo?termID={316a}
。 Unbeknownst to me, this meant the {}
stayed with the 316a
- I thought they were just like the parentheses used in a method signature for receiving a parameter, but I presume they are used for passing list
/ json
to a method (not relevant in this case). 我不知道,这意味着
{}
保留了316a
- 我认为它们就像接收参数的方法签名中使用的括号一样,但我认为它们用于将list
/ json
传递给方法(不相关)这个案例)。 This meant that when my repository query ran, it returned nothing because I was not looking for the string {316a}
. 这意味着当我的存储库查询运行时,它没有返回任何内容,因为我没有查找字符串
{316a}
。
If I call the API with the following address http://localhost:51520/api/ClassInfo?termID=316a
it works because the string 316a
gets passed to the query. 如果我使用以下地址调用API
http://localhost:51520/api/ClassInfo?termID=316a
它的工作原理是因为字符串316a
被传递给查询。
Thank you all. 谢谢你们。
I had a class inheriting from DynamicObject, and that would only return empty JSON (while XML seemed to return properly). 我有一个继承自DynamicObject的类,它只返回空的JSON(而XML似乎正确返回)。
In my case, I was able to remove the DynamicObject inheritance and JSON serialization started working. 在我的情况下,我能够删除DynamicObject继承和JSON序列化开始工作。
//didn't serialize to json, but xml worked
public MyClass : DynamicObject, IMyClass { //... }
//works for json and xml
public MyClass : IMyClass { //... }
Unfortunately, I didn't have a chance to look into why DynamicObject
breaks JSON serialization. 不幸的是,我没有机会研究为什么
DynamicObject
会破坏JSON序列化。
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