create helper classes

DotNetSolutionTools.Core/Common/SlnHelper.cs

@@ -0,0 +1,23 @@
+using Microsoft.Build.Construction;
+
+namespace DotNetSolutionTools.Core.Common;
+
+public static class SlnHelper
+{
+    public static SolutionFile? ParseSolutionFileFromPath(string solutionFilePath)
+    {
+        var solutionFile = SolutionFile.Parse(solutionFilePath);
+
+        return solutionFile;
+    }
+
+    public static List<ProjectRootElement> GetCSharpProjectObjectsFromSolutionFile(SolutionFile solutionFile)
+    {
+        var projectList = solutionFile
+            .ProjectsByGuid.Where(x => x.Value.ProjectType == SolutionProjectType.KnownToBeMSBuildFormat)
+            .Select(s => ProjectRootElement.Open(s.Value.AbsolutePath))
+            .ToList();
+
+        return projectList;
+    }
+}