Httpclient Not Supporting Postasjsonasync Method C#

HttpClient not supporting PostAsJsonAsync method C#

Yes, you need to add a reference to

System.Net.Http.Formatting.dll

This can be found in the extensions assemblies area.

A good way of achieving this is by adding the NuGet package Microsoft.AspNet.WebApi.Client to your project.

HttpClient not supporting PostAsJsonAsync method & dll in C#

The error is pretty clear. Here you can see what all the overloads of that method are. You probably want to pass the uri and the payload object, something like:

HttpResponseMessage response = client.PostAsJsonAsync("/api/webapi", [your object instance here]);

Currently, you are passing a single String, hence the error.

Also, the using statement that needs correction:

using System.Net.Http.Formatting;

Compiler can't find PostAsJsonAsync method

If you gonna use PostAsJsonAsync method then you need to use following NuGet Package.

However, if you're using DNX that it won't work because it does not support DNX (yet?).

It that case you can do the following:

var response = await client.PostAsync("api/values", new StringContent(Newtonsoft.Json.JsonConvert.SerializeObject(item);, Encoding.UTF8,"application/json"));

That should help.

C# HttpClient.PostAsJsonAsync Failing with Internal Server Error

Finally figured it out. I had to set the content type on the HttpClient object itself. Added these 2 lines in the using block and it worked!

client.DefaultRequestHeaders.Clear();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

PostAsJsonAsync() not working in .Net Core 3.1 when update project from 2.2 to 3.1 (Missing Assembly) or How to consume API POST request in .NET Core

This works for me.

Dot net core 3.x doesn't have any assembly for PostAsJsonAsync().

And Dot Net Core 2. not supported by Microsoft. So we should not use anything that not in 3.x. should not add assembly from 2.x.

The possible alternative is PostAsync();

HttpResponseMessage resNews = 
await client.PostAsync("News/GetNews", new StringContent(JsonConvert.SerializeObject(Object), 
Encoding.UTF8, "application/json"));
    
If pass only string:
    
  HttpResponseMessage resNews = 
  await client.PostAsync("News/GetNews", new StringContent("string"));

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