HeaderPropagation 2.0.0

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See the version list below for details.
Install-Package HeaderPropagation -Version 2.0.0
dotnet add package HeaderPropagation --version 2.0.0
<PackageReference Include="HeaderPropagation" Version="2.0.0" />
For projects that support PackageReference, copy this XML node into the project file to reference the package.
paket add HeaderPropagation --version 2.0.0
The NuGet Team does not provide support for this client. Please contact its maintainers for support.
#r "nuget: HeaderPropagation, 2.0.0"
#r directive can be used in F# Interactive, C# scripting and .NET Interactive. Copy this into the interactive tool or source code of the script to reference the package.
// Install HeaderPropagation as a Cake Addin
#addin nuget:?package=HeaderPropagation&version=2.0.0

// Install HeaderPropagation as a Cake Tool
#tool nuget:?package=HeaderPropagation&version=2.0.0
The NuGet Team does not provide support for this client. Please contact its maintainers for support.

This is a backport to ASP.NET Core 2.1 (and 2.2) of the HeaderPropagation middleware I had recently contributed to the ASP.NET Core project. All code is licensed under the Apache License, Version 2.0 and copyrighted by the .NET Foundation.


I believe it is a common use case which deserves to be included in ASP.NET Core. Its main use case is probably to track distributed transaction which requires the ability to pass through a transaction identifier as well as generating a new one when not present.

Given the ASP.NET Core 3.0 release is quite far away, and the current policy doesn't allow to backport new features to already shipped releases, I have created this package as recommended so it can be used today on projects based on ASP.NET Core 2.1 or 2.2.


In Startup.Configure enable the middleware:


In Startup.ConfigureServices add the required services, eventually specifying a configuration action:

services.AddHeaderPropagation(o =>
    // propagate the header if present

    // if still missing, set it with a value factory
    o.Headers.Add("User-Agent", context => "Mozilla/5.0 (trust me, I'm really Mozilla!)");

    // propagate the header if present, using a different name in the outbound request
    o.Headers.Add("Accept-Language", "Lang");

If you are using the HttpClientFactory, add the DelegatingHandler to the client configuration using the AddHeaderPropagation extension method.

services.AddHttpClient<GitHubClient>(c =>
    c.BaseAddress = new Uri("https://api.github.com/");
    c.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json");

See samples/WebApplication.


HeaderPropagationOptions contains a dictionary where the key represent the name of the header to consume from the incoming request.

Each entry define the behaviour to propagate that header as follows:

  • OutboundHeaderName determines the name of the header to be used for the outbound http requests.

  • When present, the ValueFactory is the only method used to set the value. The factory should return StringValues.Empty to not add the header.

  • If multiple configurations for the same header are present, the first which returns a value wins.

Please note the factory is called only once per incoming request and the same value will be used by all the outbound calls.

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Version Downloads Last updated
3.0.2 88,450 10/27/2019
3.0.1 28,881 5/30/2019
3.0.0 363 5/18/2019
2.0.0 33,881 5/8/2019
1.0.2 396 4/20/2019
1.0.1 5,041 4/7/2019
1.0.0 402 4/7/2019