Using the GetUnreadMemberCount() method, you can get the number of members who haven't read a specific message in a group channel. To get the most up-to-date value, the channel should first be updated through MarkAsRead() before calling GetUnreadMemberCount().
// Call the markAsRead() method when the current user views unread messages in a group channel.
groupChannel.MarkAsRead((inError)=>{if(inError != null)return;// Handle error.});// To listen to an update from all the other channel members' client apps, // implement OnReadStatusUpdated() with actions to do when notified.
SbGroupChannelHandler groupChannelHandler = new SbGroupChannelHandler
{
OnReadStatusUpdated =(inGroupChannel)=>{if(currentChannel.Url == inGroupChannel.Url){int unreadMemberCount = inGroupChannel.GetUnreadMemberCount(message);if(unreadMemberCount <=0){// All members have read the message.}else{// Some of members haven't read the message yet.}}}};
SendbirdChat.GroupChannel.AddGroupChannelHandler(UNIQUE_HANDLER_ID, groupChannelHandler);