---
title: "Error Message: 'System.Web.MimeMappings is not a Class'"
slug: "error-message-systemwebmimemappings-is-not-a-class"
description: "This article describes a solution for the following compilation error that can appear in AX 2012: 'System.Web.MimeMapping is not a class'."
tags: ["Compiling", "Lasernet Connector ", "Error message", "AX2012"]
updated: 2025-03-27T10:53:02Z
published: 2025-03-27T10:53:02Z
canonical: "kb.lasernetgroup.com/error-message-systemwebmimemappings-is-not-a-class"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://kb.lasernetgroup.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Error Message During Compiling: 'System.Web.MimeMappings is not a Class'

This article describes a solution for the following compilation error that can appear in AX 2012:

> [!CAUTION]
> Error
> 
> System.Web.MimeMapping is not a class.

![](https://cdn.document360.io/c831ef63-c6b3-48ee-b443-3e33644e4e2e/Images/Documentation/image-OD3A3SX6.png)

### Resolution

Lasernet needs at least .net version 4.5 in order to use the **Attachment** and loading of AOS/Client printers functions.

Install .net version 4.5 or later, and then compile again.