用ReactiveUI和Caliburn.Micro分页ReactiveUI

Question

我试图为使用Caliburn.Micro.ReactiveUI的列表框实现分页机制，并使用".Skip(currentPage).Take(pageSize)“调用EF。我是ReactiveUI新手，一般都是反应型的。我相信这应该很简单。

我有一个" SearchParameters“类，需要观察它，当SearchParameters对象上的任何属性发生变化时，搜索函数都需要执行。

您可以从注释掉的代码中看到，我也尝试将类定义为ReactiveObject。但是，当前的实现是使用CM的PropertyChangedBase。在我的视图中，单个属性使用CM的约定绑定文本框：

public class SearchParameters : PropertyChangedBase
    {

        private string _searchTerm;
        public string SearchTerm
        {
            get { return _searchTerm; }
            set
            {
                if (value == _searchTerm) return;
                _searchTerm = value;
                NotifyOfPropertyChange(() => SearchTerm);

            }
        }
        private int _pageSize;
        public int PageSize
        {
            get { return _pageSize; }
            set
            {
                if (value == _pageSize) return;
                _pageSize = value;
                NotifyOfPropertyChange(() => PageSize);

            }
        }

        private int _skipCount;
        public int SkipCount
        {
            get { return _skipCount; }
            set
            {
                if (value == _skipCount) return;
                _skipCount = value;
                NotifyOfPropertyChange(() => SkipCount);

            }
        }

        //private string _searchTerm;
        //public string SearchTerm
        //{
        //    get { return _searchTerm; }
        //    set { this.RaiseAndSetIfChanged(ref _searchTerm, value); }
        //}
        //private int _pageSize;
        //public int PageSize
        //{
        //    get { return _pageSize; }
        //    set { this.RaiseAndSetIfChanged(ref _pageSize, value); }
        //}

        //private int _skipCount;
        //public int SkipCount
        //{
        //    get { return _skipCount; }
        //    set { this.RaiseAndSetIfChanged(ref _skipCount, value); }
        //}

    }

"SearchService“具有以下方法，需要在SearchParameter的任何一个值更改时执行该方法：

public async Task<SearchResult> SearchAsync(SearchParameters searchParameters)
    {
        return await Task.Run(() =>
        {
            var query = (from m in _hrEntities.Departments select m);
            if (!String.IsNullOrEmpty(searchParameters.SearchTerm))
            {
                searchParameters.SearchTerm = searchParameters.SearchTerm.Trim();
                query = query.Where(
                    x => x.Employee.LastName.Contains(searchParameters.SearchTerm) || x.Employee.FirstName.Contains(searchParameters.SearchTerm)).Skip(searchParameters.SkipCount).Take(searchParameters.PageSize);
            }
            return new SearchResult
            {
                SearchTerm = searchParameters.SearchTerm,
                Matches = new BindableCollection<DepartmentViewModel>(query.Select(x => new DepartmentViewModel{ Department = x }).Skip(searchParameters.SkipCount).Take(searchParameters.PageSize))
            };
        });
    }

下面是我试图在MainViewModel的ctor中将所有这些连接起来的方法，以及Rx对我来说变得模糊的地方：

public class MainViewModel : ReactiveScreen
{
private SearchParameters _searchParameters;
        public SearchParameters SearchParameters
        {
            get { return _searchParameters; }
            set
            {
                if (value == _searchParameters) return;
                _searchParameters = value;
                NotifyOfPropertyChange(() => SearchParameters);
            }
        }
{

public void MainViewModel()
{
    var searchService = new SearchService();
    //default Skip and PageSize values
    SearchParameters = new Services.SearchParameters { SkipCount = 0 , PageSize = 10};

    var searchParameters = this.ObservableForProperty(x => x.SearchParameters)
                .Value()
                .Throttle(TimeSpan.FromSeconds(.3));
    var searchResults = searchParameters.SelectMany(parameters => searchService.SearchAsync(parameters));
            var latestMatches = searchParameters
               .CombineLatest(searchResults,    
                   (searchParameter, searchResult) =>
                       searchResult.SearchTerm != searchParameter.SearchTerm
                           ? null
                           : searchResult.Matches)
               .Where(matches => matches != null);
    _departmentViewModels = latestMatches.ToProperty(this, x => x.DepartmentViewModels);
            searchParameters.Subscribe(x => Debug.WriteLine(x));
}
}

在上面的示例中，对SearchAsync的调用不执行。似乎没有观察到SearchParameter属性的变化。

有人能告诉我我在这里做错了什么吗？

Answer 1

这是我最后是如何做到这一点的，尽管如果有人有建议的话，我很想听听其他的解决方案。我不确定这是否是最好的方法，但效果很好：

首先，我在SearchParameters类中定义了一个计算属性，该属性返回一个字符串，并在CurrentPage、SkipCount和PageSize从视图中更新时重新计算：

public string ParameterString
        {
            get { return String.Format("SearchTerm={0}|SkipCount={1}|PageSize={2}", SearchTerm, SkipCount, PageSize); }
        }

接下来，在我的MainViewModel ctor中，我只是观察计算结果，而不是试图单独对SearchTerm、SkipCount和PageSize作出反应(我最初的问题是问如何做)：

var searchTerms = this
                .ObservableForProperty(x => x.SearchParameters.ParameterString)
                .Value()
                .Throttle(TimeSpan.FromSeconds(.3));

var searchResults = searchTerms.SelectMany(parameters => SearchService.SearchAsync(parameters));
            var latestMatches = searchTerms
               .CombineLatest(searchResults,
                   (searchTerm, searchResult) =>
                       searchResult.SearchTerm != searchTerm
                           ? null
                           : searchResult.Matches)
               .Where(matches => matches != null);

最后，在我的SearchService中，我解析参数字符串以获得当前值：

var parameters = searchParameters.Split('|');
            var searchTerm = "";
            var skipCount = 0;
            var pageSize = 0;
            foreach (var parameter in parameters)
            {
                if (parameter.Contains("SearchTerm="))
                {searchTerm = parameter.Replace("SearchTerm=", "");}
                else if (parameter.Contains("SkipCount="))
                { skipCount = Convert.ToInt32(parameter.Replace("SkipCount=", "")); }
                else if (parameter.Contains("PageSize="))
                { pageSize = Convert.ToInt32(parameter.Replace("PageSize=", "")); }
            }