Formatting entities in a Twitter status message (tweet)

TwitterEntities.cs

private string FormatStatusMessageText(TwitterStatusMessage tweet) {

    // Normally we should be able to call tweet.Entities.GetAllReversed() but that method
    // will throw an exception if the array of media entities is NULL (which it is if there
    // are no media attached to the tweet).
    List<TwitterBaseEntity> entities = new List<TwitterBaseEntity>();
    entities.AddRange(tweet.Entities.HashTags);
    entities.AddRange(tweet.Entities.Urls);
    entities.AddRange(tweet.Entities.Mentions);
    if (tweet.Entities.Media != null) entities.AddRange(tweet.Entities.Media);

    // Get the original text
    string text = tweet.Text;
                
    // We read the entities from back to front so we don't break the indices while manipulating the string
    foreach (var entity in entities.OrderByDescending(x => x.StartIndex)) {

        string before = text.Substring(0, entity.StartIndex);
        string current = text.Substring(entity.StartIndex, entity.EndIndex - entity.StartIndex);
        string after = text.Substring(entity.EndIndex);

        if (entity is TwitterHashTagEntity) {
            TwitterHashTagEntity tag = (TwitterHashTagEntity) entity;
            text = before + "<a href=\"https://twitter.com/hashtag/" + tag.Text + "?src=hash\">#" + tag.Text + "</a>" + after;
        } else if (entity is TwitterUrlEntity) {
            TwitterUrlEntity url = (TwitterUrlEntity) entity;
            text = before + "<a href=\"" + url.Url + "\">" + url.DisplayUrl + "</a>" + after;
        } else if (entity is TwitterMentionEntity) {
            TwitterMentionEntity mention = (TwitterMentionEntity) entity;
            text = before + "<a href=\"https://twitter.com/" + mention.ScreenName + "\">@" + mention.ScreenName + "</a>" + after;
        } else if (entity is TwitterMediaEntity) {
            TwitterMediaEntity media = (TwitterMediaEntity) entity;
            text = before + "<a href=\"" + media.MediaUrl + "\">" + current + "</a>" + after;
        }
    }

    return text;

}