/// <summary>
        /// 获取指定工作流、角色、时间段的实例集合
        /// </summary>
        /// <param name="workflowName">流程名称</param>
        /// <param name="userIdentity">用户身份</param>
        /// <param name="role">审批角色</param>
        /// <param name="startDate">时间段起始时间</param>
        /// <param name="endDate">时间段截止时间</param>
        /// <returns></returns>
        protected override InstanceCollection Distill(string workflowName, IUserIdentity userIdentity, ApprovalRole role, DateTime startDate, DateTime endDate)
        {
            InstanceCollection collection = new InstanceCollection();
            List <StateMachineWorkflowInstance> instances = new List <StateMachineWorkflowInstance>();
            List <string> states = InstanceDistillerHelper.GetMineICanCancelStates(workflowName, role);

            if (states.Count == 0)
            {
                return(collection);
            }

            string unitCode = userIdentity.GetUserUnitCode();

            unitCode = string.IsNullOrEmpty(unitCode) ? "  " : (unitCode.Trim() + "%");
            instances.AddRange(WorkflowRuntime.Current.GetUnitList(workflowName, states.ToArray(), unitCode));
            foreach (StateMachineWorkflowInstance instance in instances)
            {
                if (instance.PersistTime >= startDate &&
                    instance.PersistTime <= endDate)
                {
                    collection.Add(new InstanceWithRole(instance, role, true));
                }
            }
            return(collection);
        }
        /// <summary>
        /// 获取指定工作流、角色、时间段的实例集合
        /// </summary>
        /// <param name="workflowName">流程名称</param>
        /// <param name="userIdentity">用户身份</param>
        /// <param name="role">审批角色</param>
        /// <param name="startDate">时间段起始时间</param>
        /// <param name="endDate">时间段截止时间</param>
        /// <returns></returns>
        protected override InstanceCollection Distill(string workflowName, IUserIdentity userIdentity, ApprovalRole role, DateTime startDate, DateTime endDate)
        {
            InstanceCollection collection = new InstanceCollection();
            List <StateMachineWorkflowInstance> instances = new List <StateMachineWorkflowInstance>();
            List <string> states = InstanceDistillerHelper.GetMineICanCancelStates(workflowName, role);

            if (states.Count == 0)
            {
                return(collection);
            }
            List <StateMachineWorkflowInstance> list = WorkflowRuntime.Current.GetListByState(workflowName, states.ToArray());

            instances.AddRange(list);

            foreach (StateMachineWorkflowInstance instance in instances)
            {
                if (instance.PersistTime >= startDate &&
                    instance.PersistTime <= endDate)
                {
                    collection.Add(new InstanceWithRole(instance, role, true));
                }
            }
            return(collection);
        }