I am trying to call a web API from my web application. I am using .Net 4.5 and while writing the code I am getting the error HttpClient
does not contain a definition PostAsJsonAsync
method.
Below is the code:
HttpClient client = new HttpClient();
client.BaseAddress = new Uri("http://localhost:51093/");
client.DefaultRequestHeaders.Accept.Add(
new MediaTypeWithQualityHeaderValue("application/json"));
var user = new Users();
user.AgentCode = 100;
user.Remarks = "Test";
user.CollectionDate = System.DateTime.Today;
user.RemittanceDate = System.DateTime.Today;
user.TotalAmount = 1000;
user.OrgBranchID = 101;
var response = client.PostAsJsonAsync("api/AgentCollection", user).Result;
and I am getting the error message:
Error: 'System.Net.Http.HttpClient' does not contain a definition for 'PostAsJsonAsync' and No extension method 'PostAsJsonAsync' accepting a first argument of type 'System.Net.Http.HttpClient' could be found (are you missing a using directive or an assembly reference?)
Please have a look and advice me.
This question is related to
c#
json
asp.net-web-api
dotnet-httpclient
The missing reference is the System.Net.Http.Formatting.dll
. But the better solution is to add the NuGet package Microsoft.AspNet.WebApi.Client
to ensure the version of the formatting dll worked with the .NET framework version of System.Net.Http
in my project.
Just expanding Jeroen's answer with the tips in comments:
var content = new StringContent(
JsonConvert.SerializeObject(user),
Encoding.UTF8,
MediaTypeNames.Application.Json);
var response = await client.PostAsync("api/AgentCollection", content);
I know this reply is too late, I had the same issue and i was adding the System.Net.Http.Formatting.Extension
Nuget, after checking here and there I found that the Nuget is added but the System.Net.Http.Formatting.dll
was not added to the references, I just reinstalled the Nuget
Ok, it is apocalyptical 2020 now, and you can find these methods in NuGet package System.Net.Http.Json
. But beware that it uses System.Text.Json
internally.
And if you really need to find out which API resides where, just use https://apisof.net/
If you are already using Newtonsoft.Json try this:
// Alternative using WebApi.Client 5.2.7
////var response = await Client.PutAsJsonAsync(
//// "api/AgentCollection", user
//// requestListDto)
var response = await Client.PostAsync("api/AgentCollection", new StringContent(
JsonConvert.SerializeObject(user), Encoding.UTF8, "application/json"));
Performance are better than JavaScriptSerializer. Take a look here https://www.newtonsoft.com/json/help/html/Introduction.htm
If you're playing around in Blazor and get the error, you need to add the package Microsoft.AspNetCore.Blazor.HttpClient
.
Try to install in your project the NuGet Package: Microsoft.AspNet.WebApi.Client:
Install-Package Microsoft.AspNet.WebApi.Client
I had this issue too on a project I'd just checked out from source control.
The symptom was the error described above and a yellow warning triangle on a reference to System.Net.Http.Formatting
To fix this, I removed the broken reference and then used NuGet to install the latest version of Microsoft.AspNet.WebApi.Client
.
For me I found the solution after a lot of try which is replacing
HttpClient
with
System.Net.Http.HttpClient
Instead of writing this amount of code to make a simple call, you could use one of the wrappers available over the internet.
I've written one called WebApiClient, available at NuGet... check it out!
https://www.nuget.org/packages/WebApiRestService.WebApiClient/
PostAsJsonAsync
is no longer in the System.Net.Http.dll
(.NET 4.5.2). You can add a reference to System.Net.Http.Formatting.dll
, but this actually belongs to an older version. I ran into problems with this on our TeamCity build server, these two wouldn't cooperate together.
Alternatively, you can replace PostAsJsonAsync
with a PostAsync
call, which is just part of new dll.
Replace
var response = client.PostAsJsonAsync("api/AgentCollection", user).Result;
With:
var response = client.PostAsync("api/AgentCollection", new StringContent(
new JavaScriptSerializer().Serialize(user), Encoding.UTF8, "application/json")).Result;
Note that JavaScriptSerializer
is in the namespace: System.Web.Script.Serialization
.
You will have to add an assembly reference in your csproj: System.Web.Extensions.dll
See https://code.msdn.microsoft.com/windowsapps/How-to-use-HttpClient-to-b9289836
As already debatted, this method isn't available anymore since .NET 4.5.2. To expand on Jeroen K's answer you can make an extension method:
public static async Task<HttpResponseMessage> PostAsJsonAsync<TModel>(this HttpClient client, string requestUrl, TModel model)
{
var serializer = new JavaScriptSerializer();
var json = serializer.Serialize(model);
var stringContent = new StringContent(json, Encoding.UTF8, "application/json");
return await client.PostAsync(requestUrl, stringContent);
}
Now you are able to call client.PostAsJsonAsync("api/AgentCollection", user)
.
Source: Stackoverflow.com