函数（ServerData）中的 MudDataGrid FilterDefinitions 和 SortDefinitions 不起作用

Question

我有这个方法可以使用 IQueryiable 动态排序和过滤：

GridState<GreenPaperItem> state = null;
private async Task<GridData<GreenPaperItem>> LoadData(GridState<GreenPaperItem> state)
{
    this.state = state;

    var query = context.GreenPaperItems.AsQueryable();
    
    if (state.FilterDefinitions != null && state.FilterDefinitions.Count() > 0)
    {
        foreach (var filter in state.FilterDefinitions)
            query = query.Where(filter.GenerateFilterFunction());
    }

    if (state.SortDefinitions != null && state.SortDefinitions.Count() > 0)
    {
        foreach (var sort in state.SortDefinitions)
            query = query.OrderBy(sort.SortFunc);
    }
    else
    {
        query = query.OrderBy(w => w.Date);
    }

    int count = query.Count();

    var items = query.Skip(state.PageSize * state.Page).Take(state.PageSize)
        .ToList<GreenPaperItem>();

    GridData<GreenPaperItem> data = new()
    {
        Items = items,
        TotalItems = count
    };
    return data;
}

但是 where 和 sort linq 方法只能获取字符串和表达式来返回 IQueryiable。方法内部的函数用红色下划线表示。如何使这项工作有效？ 错误表示无法将

IEnumaerable<GreenPaperItem>

转换为

IQueryiable<GreenPaperItem>

。

而且它不能在运行时使用此代码进行翻译：

if (state.FilterDefinitions != null && state.FilterDefinitions.Count() > 0)
{
    foreach (var filter in state.FilterDefinitions)
        query = query.Where(it => filter.GenerateFilterFunction(null)(it));
}

if (state.SortDefinitions != null && state.SortDefinitions.Count() > 0)
{
    foreach (var sort in state.SortDefinitions)
        query = query.OrderBy(it => sort.SortFunc(it));
}
else
{
    query = query.OrderBy(w => w.Date);
}

Answer 1

基于此post，它现在正在运行。但高级过滤仍然不起作用：

<MudDataGrid T="GreenPaperItem" ServerData="LoadData" Filterable="true" FilterMode="@DataGridFilterMode.ColumnFilterRow" @ref="grid">
    <Columns>
        <PropertyColumn TProperty="int" T="GreenPaperItem" Property="@(it => it.Id)"
                       Filterable="true">
            
        </PropertyColumn>
        <PropertyColumn TProperty="DateTime" T="GreenPaperItem" Property="@(it => it.Date)"
                        Filterable="true">
            <FilterTemplate>
                <MudIconButton OnClick="@OpenFilter" Icon="@_icon" Size="@Size.Small" />
                <MudOverlay Visible="@_filterOpen" OnClick="@(() => _filterOpen = false)" />
                <MudPopover Open="@_filterOpen" AnchorOrigin="Origin.BottomCenter" TransformOrigin="Origin.TopCenter" Style="width:600px">
                    <MudStack Row="true" Spacing="2" AlignItems="AlignItems.Center
      " Justify="Justify.FlexStart">
                        <MudText>Between:</MudText>
                        <MudDatePicker @bind-Date="start" t Label="Start">

                        </MudDatePicker>
                        <MudDatePicker @bind-Date="end" Label="End">

                        </MudDatePicker>
                        <MudStack Row="true">
                            <MudButton OnClick="@(() => ClearFilterAsync(context))">Clear</MudButton>
                            <MudButton Color="@Color.Primary" OnClick="@(() => ApplyFilterAsync(context))">Filter</MudButton>
                        </MudStack>
                    </MudStack>
                </MudPopover>
            </FilterTemplate>
        </PropertyColumn>
        <PropertyColumn TProperty="string" T="GreenPaperItem" Property="@(it => it.Title)">
            
        </PropertyColumn>
        <TemplateColumn CellClass="d-flex justify-end">
            <CellTemplate>
                <MudIconButton Size="@Size.Small" Icon="@Icons.Material.Outlined.Edit" OnClick="@context.Actions.StartEditingItemAsync" />
            </CellTemplate>
        </TemplateColumn>
    </Columns>
    <PagerContent>
        <MudDataGridPager T="GreenPaperItem"></MudDataGridPager>
    </PagerContent>

</MudDataGrid>

代码：

 @code {
        MudDataGrid<GreenPaperItem> grid;    
        FilterDefinition<GreenPaperItem> _filterDefinition;
        DateTime? start = DateTime.Today;
        DateTime? end = DateTime.Today;
        DateTime? filterStart = null;
        DateTime? filterEnd = null;
        string _icon = Icons.Material.Outlined.FilterAlt;
    
        bool _filterOpen = false;
    
    
        protected override async Task OnInitializedAsync()
        {
            await base.OnInitializedAsync();
            filterStart = start;
            filterEnd = end;
            _filterDefinition = new FilterDefinition<GreenPaperItem>
            {
                FilterFunction = x => x.Date.Date >= filterStart.Value.Date &&        x.Date.Date <= filterEnd.Value.Date
            };     
        }
        void OpenFilter()
        {
            _filterOpen = true;
        }
    
        private async Task ClearFilterAsync(FilterContext<GreenPaperItem> context)
        {
            filterStart = default(DateTime);
            filterEnd = default(DateTime);        
            _icon = Icons.Material.Outlined.FilterAlt;
            await context.Actions.ClearFilterAsync(_filterDefinition);
            _filterOpen = false;
        }
    
        private async Task ApplyFilterAsync(FilterContext<GreenPaperItem> context)
        {
            filterStart = start;
            filterEnd = end;       
            _icon = Icons.Material.Filled.FilterAlt;
            await context.Actions.ApplyFilterAsync(_filterDefinition);        
            _filterOpen = false;
        }
    
        GridState<GreenPaperItem> state = null;
        private async Task<GridData<GreenPaperItem>> LoadData(GridState<GreenPaperItem> state)
        {
            this.state = state;
    
            var query = context.GreenPaperItems.AsQueryable();
    
    
            if (state.FilterDefinitions != null && state.FilterDefinitions.Count() > 0)
            {
                foreach (var filter in state.FilterDefinitions)
                {
                    var expression = FilterExpressionGenerator.GenerateExpression<GreenPaperItem>
                        (filter, new FilterOptions() { FilterCaseSensitivity = DataGridFilterCaseSensitivity.Default });
                    query = query.Where(expression);
                }
            }
    
            if (state.SortDefinitions != null && state.SortDefinitions.Count() > 0)
            {
                foreach (var sort in state.SortDefinitions)
                    query = query.OrderBy($"{sort.SortBy} {(sort.Descending ? "descending" : "ascending")}");
            }
            else
            {
                query = query.OrderBy(w => w.Date);
            }
    
            bool? result = await dialogService.ShowMessageBox(
                "Warning", query.ToQueryString(), yesText: "OK", cancelText: "Cancel");
    
            int count = query.Count();
    
            var items = query.Skip(state.PageSize * state.Page).Take(state.PageSize)
                .ToList<GreenPaperItem>();
    
            GridData<GreenPaperItem> data = new()
            {
                Items = items,
                TotalItems = count
            };
            return data;
        }

如何做到这一点？