From the Lync Client Sdk you can toggle the conference "attendee video mute" by setting the ConversationProperty.ConferenceVideoHardMute on the Conversation instance.
Can example of settings the property where "value" is either true/false, where true == mute attendee video and false == unmute attendee video.
if (_conversation != null &&
_conversation.CanSetProperty(ConversationProperty.ConferenceVideoHardMute))
{
_conversation.BeginSetProperty(ConversationProperty.ConferenceVideoHardMute, value, ar =>
{
if (ar.IsCompleted)
{
try
{
_conversation.EndSetProperty(ar);
}
catch (Exception exception)
{
// exception handling
}
}
}, null);
}
or if you prefer a Task based version:
Task.Factory.FromAsync(_conversation.BeginSetProperty(ConversationProperty.ConferenceVideoHardMute, value, null, null), ar => _conversation.EndSetProperty(ar));