今天做了一个尝试，把VS2008建立的工程和解决方案，转化成VS2005的，成功了。
用VS2008建立了1个“Windows 窗体应用程序”，命名为Form1，保存退出。
Form1.sln（修改前）
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Microsoft Visual Studio Solution File, Format Version 10.00
# Visual Studio 2008
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Form1", "Form1\Form1.csproj", "{68522317-6F1A-44D6-B0CD-39E6DC21C6D6}"
EndProject
Global
GlobalSection(SolutionConfigurationPlatforms) = preSolution
Debug|Any CPU = Debug|Any CPU
Release|Any CPU = Release|Any CPU
EndGlobalSection
GlobalSection(ProjectConfigurationPlatforms) = postSolution
{68522317-6F1A-44D6-B0CD-39E6DC21C6D6}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
{68522317-6F1A-44D6-B0CD-39E6DC21C6D6}.Debug|Any CPU.Build.0 = Debug|Any CPU
{68522317-6F1A-44D6-B0CD-39E6DC21C6D6}.Release|Any CPU.ActiveCfg = Release|Any CPU
{68522317-6F1A-44D6-B0CD-39E6DC21C6D6}.Release|Any CPU.Build.0 = Release|Any CPU
EndGlobalSection
GlobalSection(SolutionProperties) = preSolution
HideSolutionNode = FALSE
EndGlobalSection
EndGlobal
————————————————————————————————————————
Form1.sln（修改后）
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Microsoft Visual Studio Solution File, Format Version 9.00
# Visual Studio 2005
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Form1", "Form1\Form1.vs2k5.csproj", "{68522317-6F1A-44D6-B0CD-39E6DC21C6D6}"
EndProject
Global
GlobalSection(SolutionConfigurationPlatforms) = preSolution
Debug|Any CPU = Debug|Any CPU
Release|Any CPU = Release|Any CPU
EndGlobalSection
GlobalSection(ProjectConfigurationPlatforms) = postSolution
{68522317-6F1A-44D6-B0CD-39E6DC21C6D6}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
{68522317-6F1A-44D6-B0CD-39E6DC21C6D6}.Debug|Any CPU.Build.0 = Debug|Any CPU
{68522317-6F1A-44D6-B0CD-39E6DC21C6D6}.Release|Any CPU.ActiveCfg = Release|Any CPU
{68522317-6F1A-44D6-B0CD-39E6DC21C6D6}.Release|Any CPU.Build.0 = Release|Any CPU
EndGlobalSection
GlobalSection(SolutionProperties) = preSolution
HideSolutionNode = FALSE
EndGlobalSection
EndGlobal
————————————————————————————————————————
Form1.csproj（修改前）
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<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="3.5" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<PropertyGroup>
<Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
<Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
<ProductVersion>9.0.30729</ProductVersion>
<SchemaVersion>2.0</SchemaVersion>
<ProjectGuid>{68522317-6F1A-44D6-B0CD-39E6DC21C6D6}</ProjectGuid>
<OutputType>WinExe</OutputType>
<AppDesignerFolder>Properties</AppDesignerFolder>
<RootNamespace>Form1</RootNamespace>
<AssemblyName>Form1</AssemblyName>
<TargetFrameworkVersion>v2.0</TargetFrameworkVersion>
<FileAlignment>512</FileAlignment>
</PropertyGroup>
……
<Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
<!-- To modify your build process, add your task inside one of the targets below and uncomment it.
Other similar extension points exist, see Microsoft.Common.targets.
<Target Name="BeforeBuild">
</Target>
<Target Name="AfterBuild">
</Target>
-->
</Project>
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Form1.csproj（修改后）
————————————————————————————————————————
<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="3.5" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
<PropertyGroup>
<Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
<Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
<ProductVersion>8.0.50727</ProductVersion>
<SchemaVersion>2.0</SchemaVersion>
<ProjectGuid>{68522317-6F1A-44D6-B0CD-39E6DC21C6D6}</ProjectGuid>
<OutputType>WinExe</OutputType>
<AppDesignerFolder>Properties</AppDesignerFolder>
<RootNamespace>Form1</RootNamespace>
<AssemblyName>Form1</AssemblyName>
<TargetFrameworkVersion>v2.0</TargetFrameworkVersion>
<FileAlignment>512</FileAlignment>
</PropertyGroup>
……
<Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
<!-- To modify your build process, add your task inside one of the targets below and uncomment it.
Other similar extension points exist, see Microsoft.Common.targets.
<Target Name="BeforeBuild">
</Target>
<Target Name="AfterBuild">
</Target>
-->
</Project>
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保存后，使用VS2005打开、编译，没有问题，不知道复杂的工程会不会有问题呢？