---
title: "Using Rest PKI on .NET"
description: "Using Rest PKI on .NET: ASP.NET MVC, Web Forms and Core sample projects, and the Lacuna.RestPki.Client NuGet package: which version fits each platform and which exceptions it throws."
canonical: "https://docs.lacunasoftware.com/en-us/articles/rest-pki/dotnet"
locale: "en"
product: "Rest PKI (legacy)"
last_updated: "2026-10-12"
---

# Using Rest PKI on .NET

Rest PKI can be used on .NET applications (C#, VB.NET, C++.NET) using a wide range of technologies and platforms.
To get started, choose one of the available samples projects:

* [ASP.NET MVC](https://docs.lacunasoftware.com/en-us/articles/rest-pki/dotnet/mvc)
* [ASP.NET Web Forms](https://docs.lacunasoftware.com/en-us/articles/rest-pki/dotnet/web-forms)
* [ASP.NET Core](https://docs.lacunasoftware.com/en-us/articles/rest-pki/dotnet/netcore)

## Client library

All .NET samples projects use the NuGet package [Lacuna.RestPki.Client](https://www.nuget.org/packages/Lacuna.RestPki.Client/)
to access Rest PKI.

### Versions and supported platforms

The package has two lines of versions, with no version between 1.24.1 and 2.2.0:

| Versions | Target frameworks |
| --- | --- |
| 1.24.1, the last 1.x version | .NET Framework 3.5, 4.0, 4.5 and 4.6; .NET Standard 1.3 and 2.0 |
| 2.2.0 and later | .NET Standard 2.0 only |

Since 2.2.0, the package is released together with [Rest PKI Core](https://docs.lacunasoftware.com/en-us/articles/rest-pki/core): its version numbers match those of
the Rest PKI Core client package, `Lacuna.RestPkiCore.Client`, which depends on it. Both lines have the same classes and send the same
requests to the Rest PKI API, so both work with pki.rest. Choose by your application's target framework:

* **.NET Framework 4.6.1 or later, .NET Core 2.0 or later, or .NET 5 or later** (platforms that implement .NET Standard 2.0): use the
  latest version.
* **.NET Framework 3.5 to 4.6, or a platform that implements only .NET Standard 1.3**: use 1.24.1.

If your application also uses `Lacuna.RestPkiCore.Client` 2.2.0 or later, keep both packages on the same version: the Rest PKI Core
client requires at least its own version of `Lacuna.RestPki.Client`.

What changes after 1.24.1: from 2.2.0, `RestPkiException.ErrorCodeStr` has the error code as text, also for codes that the
`ErrorCodes` enum does not list. 5.0.0 adds a `RestPkiClient` constructor that takes request tags, a Rest PKI Core feature that
pki.rest ignores, and the constructor that takes a `Uri` is no longer public, so pass the endpoint as a string.

The package's dependencies are all owned by either Microsoft or Lacuna Software itself. No 3rd party packages are
necessary (except for the [Newtonsoft.Json](https://www.nuget.org/packages/Newtonsoft.Json/) package, the de-facto
standard for handling JSON on .NET)

See the package [API reference](https://docs.lacunasoftware.com/en-us/api/Lacuna.RestPki.Client).

## Errors

Every exception the client throws derives from `RestException`:

| What happened | Exception | What it tells you |
| --- | --- | --- |
| Rest PKI returned HTTP 422 with the error code `ValidationError`: a certificate failed validation | `ValidationException` | `ValidationResults` |
| Rest PKI returned HTTP 422 with another error code, such as `SecurityContextRequired` | `RestPkiException` | `ErrorCode`, `Detail` |
| Rest PKI returned HTTP 401 (the access token is not valid), 500 or another error status | `RestErrorException` | `StatusCode`, `ErrorMessage` |
| No response arrived: network failure, name resolution or TLS error, or timeout | `RestUnreachableException` | `InnerException`, the cause |

`ValidationException` and `RestPkiException` are in the namespace `Lacuna.RestPki.Client`; `RestException`, `RestErrorException` and
`RestUnreachableException` are in `Lacuna.RestClient`, from the `Lacuna.RestClient` package, a dependency of this one. For HTTP 400,
403 and 404, `Lacuna.RestClient` throws a more specific subclass of `RestException` when the response body describes the error.
For the status codes and error codes, see [Return codes](https://docs.lacunasoftware.com/en-us/articles/rest-pki/return-codes).