对于VS2008等低版本与高版本VS之间的转换问题：

对照下面2个版本的不同点自由修改，切换到相应的版本文件(红字修改,灰色删除)

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低版本VS2008:

修改[解决方案文件.sln] 用记事本打开,找到如下信息:
Microsoft Visual Studio Solution File, Format Version 10.00
# Visual Studio 2008

修改工程名.csproj:

<?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>9.0.21022</ProductVersion>
    <SchemaVersion>2.0</SchemaVersion>
    <ProjectGuid>{B1B8919C-53FA-4791-8123-2734B1F723D1}</ProjectGuid>

    <TargetFrameworkVersion>v3.5</TargetFrameworkVersion>

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高版本VS2013:

修改[解决方案文件.sln] 用记事本打开,找到如下信息:

Microsoft Visual Studio Solution File, Format Version 12.00
# Visual Studio 2013
VisualStudioVersion = 12.0.31101.0
MinimumVisualStudioVersion = 10.0.40219.1

修改工程名.csproj:

<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="12.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists(‘$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props‘)" />
  <PropertyGroup>
    <Configuration Condition=" ‘$(Configuration)‘ == ‘‘ ">Debug</Configuration>
    <Platform Condition=" ‘$(Platform)‘ == ‘‘ ">AnyCPU</Platform>
    <ProjectGuid>{6022CDCE-C809-4D35-A355-72EDDE889F9F}</ProjectGuid>
    <AppDesignerFolder>Properties</AppDesignerFolder>
    <TargetFrameworkVersion>v4.0</TargetFrameworkVersion>
    <FileAlignment>512</FileAlignment>

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如果修改.net framework版本,请注意相应的修改引用的dll的目标版本号<RequiredTargetFramework>3.5</RequiredTargetFramework>

或者打开解决方案后，检查工程下的引用是否正常，不正常移除后重新引用一下

vs2008转成vs2013已经试过了没问题(解决方案,工程名都能正常打开编译运行)

修改VS解决方案及工程名,使用对应的VS版本打开项目