Exist method in D365 Table

    public static boolean Exist(TableID   id)

   {

       TableName    tableName;

       if(id != '')

        {

            select firstonly RecId from tableName where tableName.TableID   == id;

        }

        

        return (tableName.RecId != 0);

   }

Or

    public static boolean Exist()

    {

        return (select firstonly RecId from TableName).RecId != 0;

    }