打开文件提示这个错误：
用记事本打开用vs2010开发的.sln文件，这是里面的内容：
<span style="font-size:24px;">Microsoft Visual Studio Solution File, Format Version 12.00
# Visual Studio 2012
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "StudentManager", "StudentManager\StudentManager.csproj", "{A9341C8C-2E76-443F-A288-4B79C451ADFE}"
EndProject
Global
GlobalSection(SolutionConfigurationPlatforms) = preSolution
Debug|Any CPU = Debug|Any CPU
Release|Any CPU = Release|Any CPU
EndGlobalSection
GlobalSection(ProjectConfigurationPlatforms) = postSolution
{A9341C8C-2E76-443F-A288-4B79C451ADFE}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
{A9341C8C-2E76-443F-A288-4B79C451ADFE}.Debug|Any CPU.Build.0 = Debug|Any CPU
{A9341C8C-2E76-443F-A288-4B79C451ADFE}.Release|Any CPU.ActiveCfg = Release|Any CPU
{A9341C8C-2E76-443F-A288-4B79C451ADFE}.Release|Any CPU.Build.0 = Release|Any CPU
EndGlobalSection
GlobalSection(SolutionProperties) = preSolution
HideSolutionNode = FALSE
EndGlobalSection
EndGlobal
</span>
再打开用vs2010开发工程的.sln文件，这是里面的内容：
<span style="font-size:24px;">Microsoft Visual Studio Solution File, Format Version 11.00
# Visual Studio 2010
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "学生信息管理系统", "学生信息管理系统\学生信息管理系统.csproj", "{C58EB708-71E8-4301-8207-40BB0590A131}"
EndProject
Global
GlobalSection(SolutionConfigurationPlatforms) = preSolution
Debug|x86 = Debug|x86
Release|x86 = Release|x86
EndGlobalSection
GlobalSection(ProjectConfigurationPlatforms) = postSolution
{C58EB708-71E8-4301-8207-40BB0590A131}.Debug|x86.ActiveCfg = Debug|x86
{C58EB708-71E8-4301-8207-40BB0590A131}.Debug|x86.Build.0 = Debug|x86
{C58EB708-71E8-4301-8207-40BB0590A131}.Release|x86.ActiveCfg = Release|x86
{C58EB708-71E8-4301-8207-40BB0590A131}.Release|x86.Build.0 = Release|x86
EndGlobalSection
GlobalSection(SolutionProperties) = preSolution
HideSolutionNode = FALSE
EndGlobalSection
EndGlobal
</span>
两个对比一下，改一下内容就行了：
将
Microsoft Visual Studio Solution File, Format Version 12.00
# Visual Studio 2012
改为：
Microsoft Visual Studio Solution File, Format Version 11.00
# Visual Studio 2010
OK，可以打开了。。。