Difference Between Class Library Project and SQL CLR Project

In a SQL-CLR .csproj file, the <ProjectGroup> node contains two nodes not found in a Class Library .csproj file: (1) <ProjectTypeGuids>, and (2) <NoStandardLibraries>. If you remove these two nodes, you will be able to open the SQL-CLR project as a Class Library.

Excerpt from a CSPROJ File for a SQL-CLR Project¶

<?xml version="1.0" encoding="utf-8"?>
<Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <PropertyGroup>
    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
    <ProjectTypeGuids>{c252feb5-a946-4202-b1d4-9916a0590387};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
    <ProductVersion>8.0.50727</ProductVersion>
    <SchemaVersion>2.0</SchemaVersion>
    <ProjectGuid>{136D1F6D-D797-4078-97EC-EEC6B2FADBE0}</ProjectGuid>
    <OutputType>Library</OutputType>
    <NoStandardLibraries>false</NoStandardLibraries>
    <AssemblyName>Maestro.SqlClr</AssemblyName>
    <RootNamespace>Maestro.SqlClr</RootNamespace>
    <PermissionLevel>1</PermissionLevel>
  </PropertyGroup>