Code:
public string[] GetFilesAfterDate(string folder, DateTime date)
{
    FileInfo[] files = new DirectoryInfo(folder).GetFiles();
    List<FileInfo> fileList = new List<FileInfo>();

    fileList.AddRange(files);

    if (files.Length > 0)
    {
        for (int index = 0; index < files.GetUpperBound(0); index++)
        {
            if (files[index].LastWriteTime > date)
            {
                fileList.Add(files[index]);
            }
        }
    }

    string[] filePaths = new string[fileList.Count];

    for (int index = 0; index < filePaths.GetUpperBound(0); index++)
    {
        filePaths[index] = fileList[index].FullName;
    }

    return filePaths;
}