Assembly Version Incrementor

Find and increment the assembly version info in an Assembly info file

public class AssemblyVersionIncrementor
{
    public void IncrementAssemblyVersionString(FileSystemInfo fileInfo)
    {
        string[] lines = File.ReadAllLines(fileInfo.FullName);
        lines = IncrementAssemblyVersionString(lines);
        File.WriteAllLines(fileInfo.FullName, lines);
    }

    internal string[] IncrementAssemblyVersionString(string[] lines)
    {
        string[] res = new string[lines.Length];
        int ix = 0;
        foreach (string line in lines)
        {
            res[ix++] = IncrementAssemblyVersionString(line);
        }
        return res;
    }

    // Could be modified to find other types of Version Info by
    // making the "AssemblyVersion" a parameter
    internal string IncrementAssemblyVersionString(string line)
    {
        string res = line;
        if (line.Contains("AssemblyVersion"))
        {
            string newLine = string.Empty;
            string str = line;
            // Check for comments
            int commentStart = line.IndexOf("//");
            // TODO /* ... */ style comments
            if (commentStart >= 0)
            {
                str = line.Substring(0, commentStart);
            }
            if (str.Contains("AssemblyVersion"))
            {
                int start = str.IndexOf('"') + 1;
                int end = str.IndexOf('"', start);
                string assemblyVerStr = str.Substring(start, end - start);
                Version av = new Version(assemblyVerStr);
                Version newVer = av.IncrementRevision();
                newLine = line.Substring(0, start) + newVer.ToString() + 
                    line.Substring(end, line.Length - end);
            }

            res = newLine.Length > 0 ? newLine : line;
        }

        return res;
    }
}

uses the following Version extension class:

internal static class VersionExtender
{
    public static Version Increment(this Version version)
    {
        return Increment(version, 0x1L);
    }

    public static Version IncrementMajor(this Version version)
    {
        return Increment(version, 0x1000000000000L);
    }

    public static Version IncrementMinor(this Version version)
    {
        return Increment(version, 0x100000000L);
    }

    public static Version IncrementBuild(this Version version)
    {
        return Increment(version, 0x10000L);
    }

    public static Version IncrementRevision(this Version version)
    {
        return Increment(version, 0x1L);
    }


    // Good demo of using >> and << operators as well
    private static Version Increment(this Version version, ulong inc)
    {
        ulong versnNum = (((ulong)version.Major & 0xFFFF) << 48) +
            (((ulong)version.Minor & 0xFFFF) << 32) +
            (((ulong)version.Build & 0xFFFF) << 16) +
            ((ulong)version.Revision & 0xFFFF);

        versnNum += inc;

        UInt16 major = (UInt16)(versnNum >> 48);
        UInt16 minor = (UInt16)((versnNum >> 32) & 0xFFFF);
        UInt16 build = (UInt16)((versnNum >> 16) & 0xFFFF);
        UInt16 revision = (UInt16)(versnNum & 0xFFFF);

        return new Version(major, minor, build, revision);
    }
}