How to implement AppCenter Push API?

Issue

IMPORTANT - Microsoft is retiring AppCenter Push pretty soon, you can still follow my answer below to implement it. Or you can follow my new post at How to implement Push Notification in Xamarin with Firebase and Apple Push Notification with C# backend on using Firebase & Apple Push Notification. Thank you.

I have been reading https://docs.microsoft.com/en-us/appcenter/push/rest-api and looking over the Internet for example of how to implement this easily but found nothing useful.

I read and implemented this https://www.andrewhoefling.com/Blog/Post/push-notifications-with-app-center-api-integration. His solution offers very good start, but incomplete.

So I enhanced Andrew Hoefling's solution from above to a full working version and thought it's good to share with fellows Xamarin members in the answer below.

Solution

public class AppCenterPush
{
    User receiver = new User();

    public AppCenterPush(Dictionary<Guid, string> dicInstallIdPlatform)
    {
        //Simply get all the Install IDs for the receipient with the platform name as the value
        foreach(Guid key in dicInstallIdPlatform.Keys)
        {
            switch(dicInstallIdPlatform[key])
            {
                case "Android":
                    receiver.AndroidDevices.Add(key.ToString());

                    break;

                case "iOS":
                    receiver.IOSDevices.Add(key.ToString());

                    break;
            }
        }
    }

    public class Constants
    {
        public const string Url = "https://api.appcenter.ms/v0.1/apps";
        public const string ApiKeyName = "X-API-Token";     
        
        //Push required to use this. Go to https://docs.microsoft.com/en-us/appcenter/api-docs/index for instruction
        public const string FullAccessToken = "{FULL ACCESS TOKEN}";   
        
        public const string DeviceTarget = "devices_target";
        public class Apis { public const string Notification = "push/notifications"; }

        //You can find your AppName and Organization/User name at your AppCenter URL as such https://appcenter.ms/users/{owner-name}/apps/{app-name}
        public const string AppNameAndroid = "{APPNAME_ANDROID}";
        public const string AppNameIOS = "{APPNAME_IOS}";

        public const string Organization = "{ORG_OR_USER}";
    }

    [JsonObject]
    public class Push
    {
        [JsonProperty("notification_target")]
        public Target Target { get; set; }

        [JsonProperty("notification_content")]
        public Content Content { get; set; }
    }

    [JsonObject]
    public class Content
    {
        public Content()
        {
            Name = "default";   //By default cannot be empty, must have at least 3 characters
        }

        [JsonProperty("name")]
        public string Name { get; set; }

        [JsonProperty("title")]
        public string Title { get; set; }

        [JsonProperty("body")]
        public string Body { get; set; }

        [JsonProperty("custom_data")]
        public IDictionary<string, string> CustomData { get; set; }
    }

    [JsonObject]
    public class Target
    {
        [JsonProperty("type")]
        public string Type { get; set; }

        [JsonProperty("devices")]
        public IEnumerable Devices { get; set; }
    }

    public class User
    {
        public User()
        {
            IOSDevices = new List<string>();
            AndroidDevices = new List<string>();
        }

        public List<string> IOSDevices { get; set; }
        public List<string> AndroidDevices { get; set; }
    }

    public async Task<bool> Notify(string title, string message, Dictionary<string, string> customData = default(Dictionary<string, string>))
    {
        try
        {
            //title, message length cannot exceed 100 char
            if (title.Length > 100)
                title = title.Substring(0, 95) + "...";

            if (message.Length > 100)
                message = message.Substring(0, 95) + "...";

            if (!receiver.IOSDevices.Any() && !receiver.AndroidDevices.Any())
                return false; //No devices to send

            //To make sure in Android, title and message is retain when click from notification. Else it's lost when app is in background
            if (customData == null)
                customData = new Dictionary<string, string>();

            if (!customData.ContainsKey("Title"))
                customData.Add("Title", title);

            if (!customData.ContainsKey("Message"))
                customData.Add("Message", message);

            //custom data cannot exceed 100 char 
            foreach (string key in customData.Keys)
            {
                if(customData[key].Length > 100)
                {
                    customData[key] = customData[key].Substring(0, 95) + "...";
                }
            }

            var push = new Push
            {
                Content = new Content
                {
                    Title = title,
                    Body = message,
                    CustomData = customData
                },
                Target = new Target
                {
                    Type = Constants.DeviceTarget
                }
            };

            HttpClient httpClient = new HttpClient();

            //Set the content header to json and inject the token
            httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
            httpClient.DefaultRequestHeaders.Add(Constants.ApiKeyName, Constants.FullAccessToken);

            //Needed to solve SSL/TLS issue when 
            ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3 | SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12;

            if (receiver.IOSDevices.Any())
            {
                push.Target.Devices = receiver.IOSDevices;

                string content = JsonConvert.SerializeObject(push);

                HttpContent httpContent = new StringContent(content, Encoding.UTF8, "application/json");

                string URL = $"{Constants.Url}/{Constants.Organization}/{Constants.AppNameiOS}/{Constants.Apis.Notification}";

                var result = await httpClient.PostAsync(URL, httpContent);
            }

            if (receiver.AndroidDevices.Any())
            {
                push.Target.Devices = receiver.AndroidDevices;

                string content = JsonConvert.SerializeObject(push);

                HttpContent httpContent = new StringContent(content, Encoding.UTF8, "application/json");

                string URL = $"{Constants.Url}/{Constants.Organization}/{Constants.AppNameAndroid}/{Constants.Apis.Notification}";

                var result = await httpClient.PostAsync(URL, httpContent);
            }

            return true;
        }
        catch(Exception ex)
        {
            Console.WriteLine(ex.ToString());

            return false;
        }
    }
}

To use this, simply do the following from your program

 var receiptInstallID = new Dictionary<string, string>
    {
        { "XXX-XXX-XXX-XXX", "Android" },
        { "YYY-YYY-YYY-YYY", "iOS" }
    };

AppCenterPush appCenterPush = new AppCenterPush(receiptInstallID);

await appCenterPush.Notify("{YOUR_TITLE}", "{YOUR_MESSAGE}", null);

Answered By - TPG