using (var SqlCon = await Connection.GetConnection())
            {
                int count;                
                object o = null;

                using (var cmdIdsCount =
                    Command.InitializeCommandForInputIds
                        (@"GetPrivateMessagesAuthorsCount",
                            SqlCon, companionId,accountId))
                {//тут companionId=2,accountId=1
                    o = await cmdIdsCount.ExecuteScalarAsync();
                }
if (o == DBNull.Value || o == null)
                    count = 1;
                else
                    count = Convert.ToInt32(o);
}

internal static SqlCommand InitializeCommandForInputIds
           (string Function, SqlConnection SqlCon, int CompanionId, int AccountId)
        {
            SqlCommand cmd = new SqlCommand(Function, SqlCon);//тут CompanionId=2,AccountId=1 и ConnectionState=Open
            cmd.CommandType = CommandType.StoredProcedure;
            SqlParameter par = cmd.Parameters.Add(AccountIdParameter, SqlDbType.Int);
            par.Value = AccountId;
            SqlParameter par1 = cmd.Parameters.Add(CompanionIdParameter, SqlDbType.Int);
            par.Value = CompanionId;
            cmd.CommandTimeout = CmdTimeout;
            cmd.Prepare();

            return cmd;
        }

create table PrivateMessage
(
	Id INT IDENTITY(1,1) NOT NULL PRIMARY KEY,
	SenderAccountId INT NOT NULL DEFAULT 1,
	AcceptorAccountId int NOT NULL DEFAULT 1,
	PrivateText NVARCHAR(1000) NOT NULL DEFAULT N'Сообщение'	
);
insert into PrivateMessage values (1,2,N'Первое'),
(2,1,N'Второе'),
(1,2,N'Третье');
go
CREATE PROCEDURE GetPrivateMessagesAuthorsCount(@AccountId int=1, @CompanionId int=2)
AS 
BEGIN	
set nocount off;
	select count(Id)
	from PrivateMessage 
	where ((SenderAccountId=@AccountId and AcceptorAccountId=@CompanionId)
	or (SenderAccountId=@CompanionId and AcceptorAccountId=@AccountId));
	
end
go

exec GetPrivateMessagesAuthorsCount 2,1