Wrapper classes for reading solutions and projects, taken from http://stackoverflow.com/a/4634505/149259

Solution.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;

namespace MyProject.Conventions.SolutionConventions
{
    public class Solution
    {
        //internal class SolutionParser
        //Name: Microsoft.Build.Construction.SolutionParser
        //Assembly: Microsoft.Build, Version=4.0.0.0

        private static readonly Type s_SolutionParser;
        private static readonly PropertyInfo s_SolutionParser_solutionReader;
        private static readonly MethodInfo s_SolutionParser_parseSolution;
        private static readonly PropertyInfo s_SolutionParser_projects;

        static Solution()
        {
            s_SolutionParser =
                Type.GetType(
                    "Microsoft.Build.Construction.SolutionParser, Microsoft.Build, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a",
                    false, false);
            if (s_SolutionParser != null)
            {
                s_SolutionParser_solutionReader = s_SolutionParser.GetProperty("SolutionReader",
                    BindingFlags.NonPublic | BindingFlags.Instance);
                s_SolutionParser_projects = s_SolutionParser.GetProperty("Projects",
                    BindingFlags.NonPublic | BindingFlags.Instance);
                s_SolutionParser_parseSolution = s_SolutionParser.GetMethod("ParseSolution",
                    BindingFlags.NonPublic | BindingFlags.Instance);
            }
        }

        public Solution(string solutionFileName)
        {
            if (s_SolutionParser == null)
            {
                throw new InvalidOperationException(
                    "Can not find type 'Microsoft.Build.Construction.SolutionParser' are you missing a assembly reference to 'Microsoft.Build.dll'?");
            }
            var solutionParser =
                s_SolutionParser.GetConstructors(BindingFlags.Instance | BindingFlags.NonPublic).First().Invoke(null);
            using (var streamReader = new StreamReader(solutionFileName))
            {
                s_SolutionParser_solutionReader.SetValue(solutionParser, streamReader, null);
                s_SolutionParser_parseSolution.Invoke(solutionParser, null);
            }
            var projects = new List<SolutionProject>();
            var array = (Array) s_SolutionParser_projects.GetValue(solutionParser, null);
            for (int i = 0; i < array.Length; i++)
            {
                projects.Add(new SolutionProject(array.GetValue(i)));
            }
            Projects = projects;
        }

        public List<SolutionProject> Projects { get; private set; }
    }
}

SolutionProject.cs

using System;
using System.Diagnostics;
using System.Reflection;

namespace MyProject.Conventions.SolutionConventions
{
    [DebuggerDisplay("{ProjectName}, {RelativePath}, {ProjectGuid}")]
    public class SolutionProject
    {
        private static readonly Type s_ProjectInSolution;
        private static readonly PropertyInfo s_ProjectInSolution_ProjectName;
        private static readonly PropertyInfo s_ProjectInSolution_RelativePath;
        private static readonly PropertyInfo s_ProjectInSolution_ProjectGuid;
        private static readonly PropertyInfo s_ProjectInSolution_ProjectType;

        static SolutionProject()
        {
            s_ProjectInSolution =
                Type.GetType(
                    "Microsoft.Build.Construction.ProjectInSolution, Microsoft.Build, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a",
                    false, false);
            if (s_ProjectInSolution != null)
            {
                s_ProjectInSolution_ProjectName = s_ProjectInSolution.GetProperty("ProjectName",
                    BindingFlags.NonPublic | BindingFlags.Instance);
                s_ProjectInSolution_RelativePath = s_ProjectInSolution.GetProperty("RelativePath",
                    BindingFlags.NonPublic | BindingFlags.Instance);
                s_ProjectInSolution_ProjectGuid = s_ProjectInSolution.GetProperty("ProjectGuid",
                    BindingFlags.NonPublic | BindingFlags.Instance);
                s_ProjectInSolution_ProjectType = s_ProjectInSolution.GetProperty("ProjectType",
                    BindingFlags.NonPublic | BindingFlags.Instance);
            }
        }

        public string ProjectName { get; private set; }
        public string RelativePath { get; private set; }
        public string ProjectGuid { get; private set; }
        public string ProjectType { get; private set; }

        public SolutionProject(object solutionProject)
        {
            ProjectName = s_ProjectInSolution_ProjectName.GetValue(solutionProject, null) as string;
            RelativePath = s_ProjectInSolution_RelativePath.GetValue(solutionProject, null) as string;
            ProjectGuid = s_ProjectInSolution_ProjectGuid.GetValue(solutionProject, null) as string;
            ProjectType = s_ProjectInSolution_ProjectType.GetValue(solutionProject, null).ToString();
        }
    }
}