Solution file error MSB5014: File format version is not recognized.  MSBuild can only read solution files between versions 7.0 and 9.0, inclusive.

This error may occur when compiling a solution for Visual 2008 or 2010 with the MSBuild program that came with Visual Studio 2005.  The problem is that VS 2005 does not understand the newer solution file formats.  To eliminate this error, use the newest version of MSBuild available (check your system):

C:WindowsMicrosoft.NETFrameworkv3.5msbuild.exe
C:WindowsMicrosoft.NETFrameworkv4.0.30319msbuild.exe

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MSDN subscribers can download VS 2008 here. Non-subscribers can download a 90-day free trial here. The smaller, free versions of Visual Studio Express are here. Or if you just want the .NET 3.5 framework, you can find it here.

Key features of VS 2008 and .NET 3.5 include:

• Multi-Targeting – Select the .NET version against which to build an application. Thus, you can use VS 2008 to build .NET 2.0 or .NET 3.5 applications.
• Web Designer – Faster and much improved HTML designer with rich CSS support.
• AJAX – Now built-in to ASP.NET with many improvements.
• LINQ to SQL – Built-in OR/M (object-relational mapper) to model relational databases using .NET objects, then query and manage these databases using LINQ.
• Query Syntax – Declarative shorthand for expressing queries using the standard LINQ query operators.
• Anonymous Types – Concisely define inline types within code without having to explicitly define a formal class. Anonymous types are particularly useful when querying and transforming data with LINQ.
• Lambda Expressions – Provide a more concise, functional syntax for writing anonymous methods.
• Extension Methods – Add new public methods to existing types without modifying or sub-classing the original type.
• Automatic Properties – Automatically create a private field and public get/set properties.
• Object and Collection Initializers – Shorthand code for initializing objects and object collections.

Note that VS 2008 runs fine on the same PC as VS 2005, so you can install and test VS 2008 without compromising your existing VS 2005 setup. Or you can use VS 2008 and multi-targeting to build and maintain your existing .NET 2.0 applications. Also, .NET 3.5 is built upon the .NET 2.0 framework, so your .NET 2.0 applications should run fine on PCs with only .NET 3.5 installed.

VS 2008 and .NET 3.5 are terrific upgrades that continue to advance the .NET development environment. The only negative is that once again, Microsoft is releasing .NET 3.5 as a separate download and not as a required component of Windows Update. As a result, it will be at least 2-4 years before software developers can expect a majority of Windows users to have .NET 3.5 installed on their PCs, which is a real shame.