.NET 6开发TodoList应用之实现数据塑形

using System.Dynamic;

namespace TodoList.Application.Common.Interfaces;

public interface IDataShaper<T>
{
    IEnumerable<ExpandoObject> ShapeData(IEnumerable<T> entities, string fieldString);
    ExpandoObject ShapeData(T entity, string fieldString);
}

using System.Dynamic;
using System.Reflection;
using TodoList.Application.Common.Interfaces;

namespace TodoList.Application.Common;

public class DataShaper<T> : IDataShaper<T> where T : class
{
    public PropertyInfo[] Properties { get; set; }

    public DataShaper()
    {
        Properties = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance);
    }

    public IEnumerable<ExpandoObject> ShapeData(IEnumerable<T> entities, string? fieldString)
    {
        var requiredProperties = GetRequiredProperties(fieldString);

        return GetData(entities, requiredProperties);
    }

    public ExpandoObject ShapeData(T entity, string? fieldString)
    {
        var requiredProperties = GetRequiredProperties(fieldString);

        return GetDataForEntity(entity, requiredProperties);
    }

    private IEnumerable<PropertyInfo> GetRequiredProperties(string? fieldString)
    {
        var requiredProperties = new List<PropertyInfo>();

        if (!string.IsNullOrEmpty(fieldString))
        {
            var fields = fieldString.Split(',', StringSplitOptions.RemoveEmptyEntries);
            foreach (var field in fields)
            {
                var property = Properties.FirstOrDefault(pi => pi.Name.Equals(field.Trim(), StringComparison.InvariantCultureIgnoreCase));
                if (property == null)
                {
                    continue;
                }

                requiredProperties.Add(property);
            }
        }
        else
        {
            requiredProperties = Properties.ToList();
        }

        return requiredProperties;
    }

    private IEnumerable<ExpandoObject> GetData(IEnumerable<T> entities, IEnumerable<PropertyInfo> requiredProperties)
    {
        return entities.Select(entity => GetDataForEntity(entity, requiredProperties)).ToList();
    }

    private ExpandoObject GetDataForEntity(T entity, IEnumerable<PropertyInfo> requiredProperties)
    {
        var shapedObject = new ExpandoObject();
        foreach (var property in requiredProperties)
        {
            var objectPropertyValue = property.GetValue(entity);
            shapedObject.TryAdd(property.Name, objectPropertyValue);
        }

        return shapedObject;
    }
}

using System.Dynamic;
using TodoList.Application.Common.Interfaces;

namespace TodoList.Application.Common.Extensions;

public static class DataShaperExtensions
{
    public static IEnumerable<ExpandoObject> ShapeData<T>(this IEnumerable<T> entities, IDataShaper<T> shaper, string? fieldString)
    {
        return shaper.ShapeData(entities, fieldString);
    }
}

// 省略其他...
public static PaginatedList<TDestination> PaginatedListFromEnumerable<TDestination>(this IEnumerable<TDestination> entities, int pageNumber, int pageSize)
{
    return PaginatedList<TDestination>.Create(entities, pageNumber, pageSize);   
}

// 省略其他
services.AddScoped(typeof(IDataShaper<>), typeof(DataShaper<>));

using System.Dynamic;
using AutoMapper;
using AutoMapper.QueryableExtensions;
using MediatR;
using TodoList.Application.Common.Extensions;
using TodoList.Application.Common.Interfaces;
using TodoList.Application.Common.Mappings;
using TodoList.Application.Common.Models;
using TodoList.Application.TodoItems.Specs;
using TodoList.Domain.Entities;
using TodoList.Domain.Enums;

namespace TodoList.Application.TodoItems.Queries.GetTodoItems;

public class GetTodoItemsWithConditionQuery : IRequest<PaginatedList<ExpandoObject>>
{
    public Guid ListId { get; set; }
    public bool? Done { get; set; }
    public string? Title { get; set; }
    // 前端指明需要返回的字段
    public string? Fields { get; set; }
    public PriorityLevel? PriorityLevel { get; set; }
    public string? SortOrder { get; set; } = "title_asc";
    public int PageNumber { get; set; } = 1;
    public int PageSize { get; set; } = 10;
}

public class GetTodoItemsWithConditionQueryHandler : IRequestHandler<GetTodoItemsWithConditionQuery, PaginatedList<ExpandoObject>>
{
    private readonly IRepository<TodoItem> _repository;
    private readonly IMapper _mapper;
    private readonly IDataShaper<TodoItemDto> _shaper;

    public GetTodoItemsWithConditionQueryHandler(IRepository<TodoItem> repository, IMapper mapper, IDataShaper<TodoItemDto> shaper)
    {
        _repository = repository;
        _mapper = mapper;
        _shaper = shaper;
    }

    public Task<PaginatedList<ExpandoObject>> Handle(GetTodoItemsWithConditionQuery request, CancellationToken cancellationToken)
    {
        var spec = new TodoItemSpec(request);
        return Task.FromResult(
            _repository
                .GetAsQueryable(spec)
                .ProjectTo<TodoItemDto>(_mapper.ConfigurationProvider)
                .AsEnumerable()
                // 进行数据塑形和分页返回
                .ShapeData(_shaper, request.Fields)
                .PaginatedListFromEnumerable(request.PageNumber, request.PageSize)
            );
    }
}

[HttpGet]
public async Task<ApiResponse<PaginatedList<ExpandoObject>>> GetTodoItemsWithCondition([FromQuery] GetTodoItemsWithConditionQuery query)
{
    return ApiResponse<PaginatedList<ExpandoObject>>.Success(await _mediator.Send(query));
}