Programmatically Set C# Language Version across many projects

ChangeLanguageVersion.cs

using Microsoft.Build.Evaluation.Project;
using System.IO;
	void Main()
	{
		var files = Directory.GetFiles(@"c:\projects\projectRoot\", "*.csproj", SearchOption.AllDirectories);
		foreach (var file in files)
		{
			var project = new Project(file);
			project.SetProperty("LangVersion", "6");
			project.Save();
		}
	}