ASP.NET Custom control to create Google Calendar Event hyperlinks

• Download demo project and source code - 11 Kb

Introduction

Google recently released the Google Calendar application. If your website has event information, allow users to add the event to their own Google calendar easily with a Google Calendar event link.

Example link

What I've done is created a new ASP.NET HyperLink control and added some properties that allow specific information to be attached to the hyperlink control for a Google Calendar Event. Then I provided an overridden Render() function that assembles the specific NavigateUrl with the provided information, supplying defaults if necessary.

Render() code

        protected override void Render(HtmlTextWriter writer)
        {
            StringBuilder url = new StringBuilder();
            url.Append("http://www.google.com/calendar/event?");
            url.Append("action=TEMPLATE");

            // Event title

            string eventText = this.EventTitle;
            if (string.IsNullOrEmpty(eventText))
            {
                eventText = this.Text;
            }
            if (!string.IsNullOrEmpty(eventText))
            {
                url.AppendFormat("&text={0}", HttpUtility.UrlEncode(eventText));
            }

            // Event dates

            // TODO: Validate that a start or end date has been specified

            url.Append("&dates=");
            if (this.StartDateTime != null)
            {
                if (this.AllDayEvent || (this.StartDateTime == this.EndDateTime))
                {
                    url.AppendFormat("{0}/{0}", this.StartDateTime.ToString("yyyyMMdd"));
                }
                else
                {
                    // TODO: Validate that EndDateTime is set,

                    // because this is not an all day event

                    const string UTCFORMATSTRING = "yyyyMMdd\\THHmmss\\Z";
                    url.AppendFormat("{0}/{1}",
    this.StartDateTime.ToUniversalTime().ToString(UTCFORMATSTRING),
    this.EndDateTime.ToUniversalTime().ToString(UTCFORMATSTRING));
                }
            }

            // TODO: Apparently on sprop is required by google,

            // so validate that one is specified

            // Organization info

            if (!string.IsNullOrEmpty(this.OrganizerName))
            {
                url.AppendFormat("&sprop=name:{0}", HttpUtility.UrlEncode(this.OrganizerName));
            }
            if (!string.IsNullOrEmpty(this.OrganizerWebsite))
            {
                url.AppendFormat("&sprop=website:{0}", HttpUtility.UrlEncode(this.OrganizerWebsite));
            }

            // Event location

            if (!string.IsNullOrEmpty(this.EventLocation))
            {
                url.AppendFormat("&location={0}", HttpUtility.UrlEncode(this.EventLocation));
            }

            // Event description

            if (!string.IsNullOrEmpty(this.EventDescription))
            {
                url.AppendFormat("&details={0}", HttpUtility.UrlEncode(this.EventDescription));
            }

            // Free/Busy

            // Only add to url if true since default false and url could already be really long

            if (this.MarkAsBusy)
            {
                url.AppendFormat("&trp={0}", this.MarkAsBusy);
            }

            // Set the NavigateUrl

            this.NavigateUrl = url.ToString();
            base.Render(writer);
        }
    }

This is my first stab at a server control (I usually just write user controls) so let me know if there are problems, but please be gentle :)

See also

• GCal Url Generator