LineSDK - LINE Messaging API Wrapper

Custom SDK for LINE Messaging API integration.

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API Requirements & Account Types

LINE Account Types (Shield Icons)

Account Type	Icon	Verification	Features Available
Unverified	🔘 Grey	None	Basic messaging only
Verified	🔵 Blue	Business verified	Group Member APIs
Premium	🟢 Green	Premium plan	All features

Feature Availability by Account Type

API / Feature	🔘 Grey	🔵 Blue	🟢 Green	Notes
Push Message	✅	✅	✅	Basic feature
Reply Message	✅	✅	✅	Basic feature
Multicast	✅	✅	✅	Up to 500 users
Broadcast	❌	✅	✅	All followers
Get User Profile	✅	✅	✅	1:1 chat only
Get Group Summary	✅	✅	✅	Group name, picture
Get Group Member IDs	❌	✅	✅	Verified+ required!
Get Group Member Profile	❌	✅	✅	Verified+ required!
Get Group Member Count	❌	✅	✅	Verified+ required!
Get Follower IDs	❌	✅	✅	Verified+ required
Rich Menu	✅	✅	✅	Basic feature

Important Behaviors

Push to Blocked User (Silent Failure)

⚠️ WARNING: Push to blocked user returns 200 OK (no error)

When you push a message to a user who has blocked your bot:

• API returns 200 OK (success)
• No error thrown
• Message is NOT delivered
• You cannot detect this failure!

Workaround: Check follow status before pushing:

// Check if user is following before push
var profile = await lineClient.Profile.GetUserProfileAsync(userId);
if (profile == null)
{
    // User may have blocked or unfollowed
    logger.LogWarning("Cannot reach user {UserId}", userId);
}

Group Limitations

Limitation	Value	Notes
Max bots per group	1	Cannot add multiple bots
Group member limit	500	LINE group limit
Message length	5,000 chars	Per message

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Service Reference

ILineProfile (Profile Service)

public interface ILineProfile
{
    // ✅ Available for all account types
    Task<LineUserProfile?> GetUserProfileAsync(string userId);
    Task<LineGroupSummary?> GetGroupSummaryAsync(string groupId);

    // ⚠️ VERIFIED+ ACCOUNT REQUIRED
    Task<LineUserProfile?> GetGroupMemberProfileAsync(string groupId, string userId);
    Task<int> GetGroupMemberCountAsync(string groupId);
    Task<LineFollowersResult> GetGroupMemberIdsAsync(string groupId, string? continuationToken = null);

    // ⚠️ VERIFIED+ ACCOUNT REQUIRED
    Task<LineFollowersResult> GetFollowerIdsAsync(string? continuationToken = null);
}

ILineMessaging (Messaging Service)

public interface ILineMessaging
{
    // ✅ Available for all account types
    Task PushAsync(string message, string to);
    Task PushAsync(ILineMessage message, string to);
    Task ReplyAsync(string message, string replyToken);
    Task MulticastAsync(string message, IEnumerable<string> userIds);

    // ⚠️ VERIFIED+ ACCOUNT REQUIRED
    Task BroadcastAsync(string message);
    Task BroadcastAsync(ILineMessage message);
}

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Error Handling

Common Error Codes

Status	Code	Meaning
400	Invalid request	Check request body format
401	Unauthorized	Invalid channel access token
403	Forbidden	Feature requires Verified+ account
404	Not found	User/group not found or not reachable
429	Rate limited	Too many requests

Handling 403 Forbidden

try
{
    var memberIds = await lineClient.Profile.GetGroupMemberIdsAsync(groupId);
}
catch (HttpRequestException ex) when (ex.StatusCode == HttpStatusCode.Forbidden)
{
    // This API requires Verified (Blue) or Premium (Green) account
    logger.LogError("GetGroupMemberIds requires Verified+ account. " +
        "Apply for verification at LINE Developers Console.");
}

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Rate Limits

API Type	Limit	Notes
Push/Reply	100,000/min	Per channel
Multicast	100,000/min	Per channel
Broadcast	100,000/min	Verified+ only
Profile APIs	2,000/min	Per channel

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Official Documentation

• LINE Messaging API
• Account Types
• Get Group Member IDs
• Rate Limits

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Version History

Version	Date	Changes
1.1.0	2025-12-23	Added API requirements documentation
1.0.0	2025-12-01	Initial release