Question

您是否知道增量收集的替代方法，例如wpf ISupportIncrementalLoading？

Answer 1

我认为没有任何答案;（出于这个原因，我将在这里发布我的实现。图书馆仍然是BETA版本，如果您有任何问题，请向您发送问题。

  /// P.Zh. 
public class IncrementalLoadingCollection<T, TT> : ObservableCollection<TT>, ISupportIncrementalLoading
     where T : IIncrementalSource<TT>, new()
    {
        private T source;
        private int itemsPerPage;
        private bool hasMoreItems;
        private int currentPage;

        public IncrementalLoadingCollection(int itemsPerPage = 20)
        {
            this.source = new T();
            this.itemsPerPage = itemsPerPage;
            this.hasMoreItems = true;
        }

        public bool HasMoreItems
        {
            get { return hasMoreItems; }
        }

        public async Task<LoadMoreItemsResult> LoadMoreItemsAsync(uint count)
        {
            var task = Task.Factory.StartNew(async () =>
            {
                uint resultCount = 0;
                var result = await source.GetPagedItems(null, currentPage++, itemsPerPage);
                if (result == null || result.Count() == 0)
                {
                    hasMoreItems = false;
                }
                else
                {
                    resultCount = (uint)result.Count();
                    Deployment.Current.Dispatcher.BeginInvoke(() =>
                    {
                        foreach (TT item in result)
                            this.Add(item);
                    });
                }
                return new LoadMoreItemsResult() { Count = resultCount };
            }
            // ,CancellationToken.None, TaskCreationOptions.None, TaskScheduler.Default            
            ).Unwrap();           
            return task.Result;
        }       
    }

    public interface IIncrementalSource<T>
    {
        /// <summary>
        /// Get Chunk of data in specific interval from a colection
        /// </summary>
        /// <param name="o">custome object</param>
        /// <param name="pageIndex">uint start position</param>
        /// <param name="pageSize">uint end position</param>
        /// <returns>Result is chunk</returns>
        Task<IEnumerable<T>> GetPagedItems(object o, int pageIndex, int pageSize);
        bool HasMoreItems { get; set; }
    }

    public interface ISupportIncrementalLoading
    {
        bool HasMoreItems { get;  }
        Task<LoadMoreItemsResult> LoadMoreItemsAsync(uint count);
    }

    public interface IIncrementalResult<T>
    {
        IEnumerable<T> Items { get; }
        int VirtualCount { get; }
    }

    public struct LoadMoreItemsResult
    {
        public uint Count { get; set; }
    }

增量集合加载Silverlight / ISupportIncrementalLoading

1 个答案: