Hints: migration from VS2008SP1 -> VS2010Ultimate

1. The 2nd line of the project file has being changed

<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="3.5" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003"> 

<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="4.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003"> 

When you try to open the migrated project with VS2008 you simply get the following warning:

Project file contains ToolsVersion="4.0", which is not supported by this version of MSBuild. Treating the project as if it had ToolsVersion="3.5".

...all the rest work fine!

2. A whole set of new elements has being added to the default PropertyGroup of the project; all these are not breaking when you try to open the migrated project with VS2008.

<FileUpgradeFlags> 
</FileUpgradeFlags> 
<OldToolsVersion>3.5</OldToolsVersion> 
<UpgradeBackupLocation /> 
<PublishUrl>http://localhost/Utilities/</PublishUrl> 
<Install>true</Install> 
<InstallFrom>Web</InstallFrom> 
<UpdateEnabled>true</UpdateEnabled> 
<UpdateMode>Foreground</UpdateMode> 
<UpdateInterval>7</UpdateInterval> 
<UpdateIntervalUnits>Days</UpdateIntervalUnits> 
<UpdatePeriodically>false</UpdatePeriodically> 
<UpdateRequired>false</UpdateRequired> 
<MapFileExtensions>true</MapFileExtensions> 
<ApplicationRevision>0</ApplicationRevision> 
<ApplicationVersion>1.0.0.%2a</ApplicationVersion> 
<IsWebBootstrapper>true</IsWebBootstrapper> 
<UseApplicationTrust>false</UseApplicationTrust> 
<BootstrapperEnabled>true</BootstrapperEnabled> 

3. A new element has being added on the PropertyGroup of each configuration; also nothing breaking... VS2008SP1 ignores them.

<CodeAnalysisRuleSet>AllRules.ruleset</CodeAnalysisRuleSet> 

4. A new ItemGroup have being added; also nothing breaking... VS2008SP1 ignores them.

<ItemGroup> 
  <BootstrapperPackage Include="Microsoft.Net.Client.3.5"> 
    <Visible>False</Visible> 
    <ProductName>.NET Framework 3.5 SP1 Client Profile</ProductName> 
    <Install>false</Install> 
  </BootstrapperPackage> 
  <BootstrapperPackage Include="Microsoft.Net.Framework.3.5.SP1"> 
    <Visible>False</Visible> 
    <ProductName>.NET Framework 3.5 SP1</ProductName> 
    <Install>true</Install> 
  </BootstrapperPackage> 
  <BootstrapperPackage Include="Microsoft.VisualBasic.PowerPacks.10.0"> 
    <Visible>False</Visible> 
    <ProductName>Microsoft Visual Basic PowerPacks 10.0</ProductName> 
    <Install>true</Install> 
  </BootstrapperPackage> 
  <BootstrapperPackage Include="Microsoft.Windows.Installer.3.1"> 
    <Visible>False</Visible> 
    <ProductName>Windows Installer 3.1</ProductName> 
    <Install>true</Install> 
  </BootstrapperPackage> 
</ItemGroup> 

5. If your projects have being set to "Treat warnings as errors" then VS2010 is much more sensitive, especially to xmldocumentation mistakes.