如何使用HttpClient在C＃中使用Json查询

Question

I am using C# to connect to IBM Cloudant. IBM Cloudant supports JSON queries IBM Cloudant , it is mentioned that I need to use a POST request in order to create a query but it is not explained, I am using HttpClient which has a method PostAsync method. Does anyone have an idea how to use this method to create a query for example the following query:

{
   "selector": {
      "_id": {
         "$gt": null
      }
   }
}

Answer 1

I had some confusion about this as well. Please refer to below.

var client = new HttpClient();

var content = new StringContent("JSON Content");
content.Headers.Add("header-name", "header value");

client.PostAsync("http://example.com/something", content);

Your JSON content can also be a C# object, which you could JSON serialize using something like Newtonsoft.Json

Answer 2

You could also try this version, classes for your query

public class Id{
    public object gt { get; set; }
}

public class Selector{
    public Id _id { get; set; }
}

public class RootObject{
    public Selector selector { get; set; }
}

serialize tmpObject and PostAsync:

client.PostAsync(url, new StringContent(tmpObject.ToString(), Encoding.UTF8, "application/json"));

Answer 3

so i finally managed to retrieve the response of the query it is as follows: var jsonString = "{\\"selector\\": {\\"_id\\": {\\"$gt\\": null}},\\"fields\\": [\\"" + Attribute + "\\"],\\"sort\\": [{\\"_id\\": \\"asc\\"}]}"; var content = new StringContent(jsonString, Encoding.UTF8, "application/json"); HttpResponseMessage res = await Client.PostAsync(string.Format("https://{0}.cloudant.com/{1}/_find", User, Database), content); StreamReader streamReader = new StreamReader(await res.Content.ReadAsStreamAsync()); JObject responseContent = (JObject)JToken.ReadFrom(new JsonTextReader(streamReader)); streamReader.Close(); var Elements =responseContent["docs"].Value<JArray>(); var jsonString = "{\\"selector\\": {\\"_id\\": {\\"$gt\\": null}},\\"fields\\": [\\"" + Attribute + "\\"],\\"sort\\": [{\\"_id\\": \\"asc\\"}]}"; var content = new StringContent(jsonString, Encoding.UTF8, "application/json"); HttpResponseMessage res = await Client.PostAsync(string.Format("https://{0}.cloudant.com/{1}/_find", User, Database), content); StreamReader streamReader = new StreamReader(await res.Content.ReadAsStreamAsync()); JObject responseContent = (JObject)JToken.ReadFrom(new JsonTextReader(streamReader)); streamReader.Close(); var Elements =responseContent["docs"].Value<JArray>();