使用 HttpClient PostAsJsonAsync 在 ASP.NET Core 中发送 HTTP POST 消息

Question

I want to send dynamic object like

new { x = 1, y = 2 };

as body of HTTP POST message. So I try to write

var client = new HttpClient();

but I can't find method

client.PostAsJsonAsync()

So I tried to add Microsoft.AspNetCore.Http.Extensions package to project.json and add

using Microsoft.AspNetCore.Http.Extensions; 

to uses clause. However It didn't help me.

So what is the easiest way to send POST request with JSON body in ASP.NET Core?

Answer 1

You should add reference to "Microsoft.AspNet.WebApi.Client" package (read this article for samples).

Without any additional extension, you may use standard PostAsync method:

client.PostAsync(uri, new StringContent(jsonInString, Encoding.UTF8, "application/json"));

where jsonInString value you can get by calling JsonConvert.SerializeObject(<your object>);

Answer 2

I use this class:

public class JsonContent : StringContent
{
    public JsonContent(object obj) :
        base(JsonConvert.SerializeObject(obj), Encoding.UTF8, "application/json")
    { }
}

Sample of usage:

new HttpClient().PostAsync("http://...", new JsonContent(new { x = 1, y = 2 }));

Answer 3

I would add to the accepted answer that you would also want to add the Accept header to the httpClient :

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

Answer 4

Microsoft now recommends using an IHttpClientFactory with the following benefits:

• Provides a central location for naming and configuring logical HttpClient instances. For example, a client named github could be registered and configured to access GitHub. A default client can be registered for general access.
• Codifies the concept of outgoing middleware via delegating handlers in HttpClient . Provides extensions for Polly-based middleware to take advantage of delegating handlers in HttpClient .
• Manages the pooling and lifetime of underlying HttpClientMessageHandler instances. Automatic management avoids common DNS (Domain Name System) problems that occur when manually managing HttpClient lifetimes.
• Adds a configurable logging experience (via ILogger ) for all requests sent through clients created by the factory.

https://docs.microsoft.com/en-us/aspnet/core/fundamentals/http-requests?view=aspnetcore-3.1

Setup:

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddHttpClient();
        // Remaining code deleted for brevity.

POST example:

public class BasicUsageModel : PageModel
{
    private readonly IHttpClientFactory _clientFactory;

    public BasicUsageModel(IHttpClientFactory clientFactory)
    {
        _clientFactory = clientFactory;
    }
    
    public async Task CreateItemAsync(TodoItem todoItem)
    {
        var todoItemJson = new StringContent(
            JsonSerializer.Serialize(todoItem, _jsonSerializerOptions),
            Encoding.UTF8,
            "application/json");
            
        var httpClient = _clientFactory.CreateClient();
        
        using var httpResponse =
            await httpClient.PostAsync("/api/TodoItems", todoItemJson);
    
        httpResponse.EnsureSuccessStatusCode();
    }

https://docs.microsoft.com/en-us/aspnet/core/fundamentals/http-requests?view=aspnetcore-3.1#make-post-put-and-delete-requests

Answer 5

You can use IEnterprise.Easy-HTTP since it has built in class parsing:

await new RequestBuilder<ExampleObject>()
.SetHost("https://httpbin.org")
.SetContentType(ContentType.Application_Json)
.SetType(RequestType.Post)
.SetModelToSerialize(dto)
.Build()
.Execute();

Answer 6

You are right that this has long since been implemented in .NET Core.

At the time of writing (September 2019), the project.json file of NuGet 3.x+ has been superseded by PackageReference (as explained at https://docs.microsoft.com/en-us/nuget/archive/project-json ).

To get access to the *Async methods of the HttpClient class, your .csproj file must be correctly configured.

Open your .csproj file in a plain text editor, and make sure the first line is
<Project Sdk="Microsoft.NET.Sdk.Web">
(as pointed out at https://docs.microsoft.com/en-us/dotnet/core/tools/project-json-to-csproj#the-csproj-format ).

To get access to the *Async methods of the HttpClient class, you also need to have the correct package reference in your .csproj file, like so:

<ItemGroup>
    <!-- ... -->
    <PackageReference Include="Microsoft.AspNetCore.App" />
    <!-- ... -->
</ItemGroup>

(See https://docs.microsoft.com/en-us/nuget/consume-packages/package-references-in-project-files#adding-a-packagereference . Also: We recommend applications targeting ASP.NET Core 2.1 and later use the Microsoft.AspNetCore.App metapackage , https://docs.microsoft.com/en-us/aspnet/core/fundamentals/metapackage )

Methods such as PostAsJsonAsync , ReadAsAsync , PutAsJsonAsync and DeleteAsync should now work out of the box. (No using directive needed.)

Update: The PackageReference tag is no longer needed in .NET Core 3.0.

Answer 7

You can (and should) use the PostAsJsonAsync extension method from System.Net.Http.Json :

httpClient.PostAsJsonAsync(url, { 
    x = 1, 
    y = 2 
});