# .Net Core 後台FCM推播
###### tags: `.net core` `FCM` `推播`

使用Firebase進行推播，方法相當單純

[chrome推播測試工具](https://github.com/GoogleChrome/chrome-extensions-samples)
[工具使用說明](https://ithelp.ithome.com.tw/articles/10211813)

## 在FireBase上建立專案

https://console.firebase.google.com/

建立好的樣子

## 使用FirebaseAdmin

需安裝套件FirebaseAdmin

https://firebase.google.com/docs/cloud-messaging/send-message?authuser=0#admin_sdk_error_reference

https://github.com/firebase/firebase-admin-dotnet/blob/d44de7bb50bedec5ff1ee5944d7eecd064b068e6/FirebaseAdmin/FirebaseAdmin.Snippets/FirebaseMessagingSnippets.cs#L327-L341

### 啟動FirebaseAdmin

### 建立私鑰

產生私鑰後會下載私鑰的json檔案


### 服務初始化

可在需要時才執行來開啟，此處選擇網站開啟時即啟動(重複啟動會報錯)！

#### Program.cs(.Net 5以下Startup)

string path = builder.Environment.ContentRootPath + "firebase-adminsdk.json";
FirebaseApp.Create(new AppOptions()
{
    Credential = GoogleCredential.FromFile(path),
    ServiceAccountId = "[e-mail]",
});

### 對單一設備發送請求

var message = new Message()
{
    Data = new Dictionary<string, string>()
    {
        { "score", "850" },
        { "time", "2:45" },
    },
    Token = "",
};
string response = await FirebaseMessaging.DefaultInstance.SendAsync(message);

### 對多個設備發送請求

var registrationTokens = new List<string>()
{
    "YOUR_REGISTRATION_TOKEN_1",
    // ...
    "YOUR_REGISTRATION_TOKEN_n",
};
var message = new MulticastMessage()
{
    Tokens = registrationTokens,
    Data = new Dictionary<string, string>()
    {
        { "score", "850" },
        { "time", "2:45" },
    },
};

var response = await FirebaseMessaging.DefaultInstance.SendMulticastAsync(message);

### 設備主題註冊與取消註冊

[HttpPost] //主題註冊
public async Task<string> SubscribeToTopicAsync([FromBody] DeviceRegistrationModel request)
{
    var response = await FirebaseMessaging.DefaultInstance.SubscribeToTopicAsync(request.DeviceId, request.Topic);
    return response.ToString();
}
[HttpPost] //取消註冊
public async Task<string> UnsubscribeFromTopicAsync([FromBody] DeviceRegistrationModel request)
{
    var response = await FirebaseMessaging.DefaultInstance.UnsubscribeFromTopicAsync(request.DeviceId, request.Topic);
    return response.ToString();
}

### 對主題進行推播

var message = new Message()
{
    Data = new Dictionary<string, string>()
    {
        { "score", "850" },
        { "time", "2:45" },
    },
    Topic = topic,
};

// Send a message to the devices subscribed to the provided topic.
string response = await FirebaseMessaging.DefaultInstance.SendAsync(message);

## 使用FirebaseApi

### 1.點選齒輪進入專案設定


### 2.在雲端通訊建立伺服器金鑰

建立好金鑰之後，伺服器金鑰跟寄件者ID就是我們後端會用到的東西了。

可以將金鑰跟senderId寫入appsetting EX:`_configuration["FCM:SenderId"]`

### 3.後端內容

    [HttpPost]
        public string SendPushNotification([FromBody] NotificationData request)
        {
            try
            {
                //FCM伺服器金鑰
                string applicationID = "AAAASLO7bNM:APA91bHeSO8oechmbvPkVaIe9_BAAuZsXFax9YK6LH9AJAVS4_LVKyIy0w9xCx1dG-JRdazIjqyu9IjxSMJXorBh-lHPJ7LrpddZT_L65lmNZGy2FFyW6p1TstN1mZ8dVjKWIj4nFRtp";
                //SenderId
                string senderId = "312253050067";
                //Service url
                string url = "https://fcm.googleapis.com/fcm/send";
                //設備ID
                string deviceId = null;
                if (request.topic)
                    deviceId = "/topics/" + request.DeviceId;
                else
                    deviceId = request.DeviceId;
                //要推播的資料
                var data = new
                {
                    to = deviceId,
                    notification = new
                    {
                        body = request.Body,
                        title = request.Title,
                        sound = "Enabled"
                    },              
                };
                var json = JsonConvert.SerializeObject(data);
                Byte[] byteArray = Encoding.UTF8.GetBytes(json);
                HttpClient client = new HttpClient();
                var httpRequestMessage = new HttpRequestMessage();
                httpRequestMessage.Method = HttpMethod.Post;
                httpRequestMessage.RequestUri = new Uri(url);
                httpRequestMessage.Content = new StringContent(json, Encoding.UTF8, "application/json");
                httpRequestMessage.Headers.Add(HttpRequestHeader.ContentType.ToString(), "application/json");
                httpRequestMessage.Headers.TryAddWithoutValidation("Authorization",string.Format("key={0}", applicationID));
                httpRequestMessage.Headers.TryAddWithoutValidation("Sender", string.Format("id={0}", senderId)); //Sender沒有也沒關係，為了防止之後需要一樣寫出來註記
                httpRequestMessage.Headers.Add(HttpRequestHeader.ContentLength.ToString(), byteArray.Length.ToString());          
                HttpResponseMessage response = client.SendAsync(httpRequestMessage).Result;
                if(response.StatusCode == HttpStatusCode.OK)
                {
                    //return "推播成功";
                    return response.ReasonPhrase.ToString();
                }
                else
                {
                    return response.ReasonPhrase.ToString();
                }           

            }
            catch (Exception ex)
            {         
                Console.WriteLine("{0:s}推播失敗：{1}", DateTime.Now, ex.Message);
                return ex.Message;
            }
        }       

### Model

public class NotificationData
{
    public string DeviceId { get; set; }
    public string Title { get; set; }
    public string Body { get; set; }
    public bool topic { get; set; }

}