参照 草根专栏- ASP.NET Core + Ng6 实战：https://v.qq.com/x/page/v07647j3zkq.html
翻页, 过滤, 排序等 – 如何传递参数?
Query String
- http://localhost:5000/api/country?pageIndex=12&pageSize=10&orderBy=id
使用抽象父类 QueryParameters, 包含常见参数:
- PageIndex, PageSize, OrderBy …
一、翻页：
1、在Core.Entity 中添加 QueryParameters.cs 类
namespace BlogDemo.Core.Entities
{
public abstract class QueryParameters : INotifyPropertyChanged
{
private const int DefaultPageSize = ;
private const int DefaultMaxPageSize = ; private int _pageIndex;
public int PageIndex
{
get => _pageIndex;
set => _pageIndex = value >= ? value : ;
} private int _pageSize = DefaultPageSize;
public virtual int PageSize
{
get => _pageSize;
set => SetField(ref _pageSize, value);
} private string _orderBy;
public string OrderBy
{
get => _orderBy;
set => _orderBy = value ?? nameof(IEntity.Id);
} private int _maxPageSize = DefaultMaxPageSize;
protected internal virtual int MaxPageSize
{
get => _maxPageSize;
set => SetField(ref _maxPageSize, value);
} public string Fields { get; set; } public event PropertyChangedEventHandler PropertyChanged; protected void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
} protected bool SetField<T>(ref T field, T value, [CallerMemberName] string propertyName = null)
{
if (EqualityComparer<T>.Default.Equals(field, value))
{
return false;
}
field = value;
OnPropertyChanged(propertyName);
if (propertyName == nameof(PageSize) || propertyName == nameof(MaxPageSize))
{
SetPageSize();
}
return true;
} private void SetPageSize()
{
if (_maxPageSize <= )
{
_maxPageSize = DefaultMaxPageSize;
}
if (_pageSize <= )
{
_pageSize = DefaultPageSize;
}
_pageSize = _pageSize > _maxPageSize ? _maxPageSize : _pageSize;
}
}
}
2、在BlogDemo.Core.Entities 中添加 PostParameters.cs 类
namespace BlogDemo.Core.Entities
{
public class PostParameters:QueryParameters
{
public string Title { get; set; }
}
}
3、 修改 BlogDemo.Infrastructure.Repositories 文件夹 的 PostRepository类 中的 方法
public async Task<PaginatedList<Post>> GetPostsAsync(PostParameters parameters)
{ var Query = _myContext.Posts.AsQueryable(); Query = Query.OrderBy(x => x.Id); var count = await Query.CountAsync();
var data = await Query.Skip(parameters.PageIndex * parameters.PageSize).Take(parameters.PageSize).ToListAsync();
return new PaginatedList<Post>(parameters.PageIndex, parameters.PageSize,count,data);
}
4、修改Controller中的Action
public async Task<PaginatedList<Post>> GetPostsAsync(PostParameters parameters)
{ var Query = _myContext.Posts.AsQueryable();
Query = Query.OrderBy(x => x.Id);
var count = await Query.CountAsync();
var data = await Query.Skip(parameters.PageIndex * parameters.PageSize).Take(parameters.PageSize).ToListAsync();
return new PaginatedList<Post>(parameters.PageIndex, parameters.PageSize,count,data);
}
二、返回翻页元数据
- 如果将数据和翻页元数据一起返回:
响应的body不再符合Accept Header了(不是资源的application/json), 这是一种新的media type.
违反REST约束, API消费者不知道如何通过application/json这个类型来解释响应的数据.
- 翻页数据不是资源表述的一部分, 应使用自定义Header (“X-Pagination”).
- 存放翻页数据的类: PaginatedList<T>可以继承于List<T>.
1、添加存放翻页数据的类：PaginatedList<T>可以继承于List<T>：
namespace BlogDemo.Core.Entities
{
public class PaginatedList<T> : List<T> where T : class
{
public int PageSize { get; set; }
public int PageIndex { get; set; } private int _totalItemsCount;
public int TotalItemsCount
{
get => _totalItemsCount;
set => _totalItemsCount = value >= ? value : ;
} public int PageCount => TotalItemsCount / PageSize + (TotalItemsCount % PageSize > ? : ); public bool HasPrevious => PageIndex > ;
public bool HasNext => PageIndex < PageCount - ; public PaginatedList(int pageIndex, int pageSize, int totalItemsCount, IEnumerable<T> data)
{
PageIndex = pageIndex;
PageSize = pageSize;
TotalItemsCount = totalItemsCount;
AddRange(data);
}
}
}
2、修改PostRepository..cs 中的Get方法
public async Task<PaginatedList<Post>> GetPostsAsync(PostParameters parameters)
{ var Query = _myContext.Posts.AsQueryable();
Query = Query.OrderBy(x => x.Id);
var count = await Query.CountAsync();
var data = await Query.Skip(parameters.PageIndex * parameters.PageSize).Take(parameters.PageSize).ToListAsync();
return new PaginatedList<Post>(parameters.PageIndex, parameters.PageSize,count,data);
}
3、修改Controller中的Action
public async Task<IActionResult> Get(PostParameters parameters)
{
var posts = await _postRepository.GetPostsAsync(parameters);
var postDto=_mapper.Map<IEnumerable<Post>,IEnumerable<PostDTO>>(posts); var meta = new
{
PageSize = posts.PageSize,
PageIndex = posts.PageIndex,
TotalItemCount = posts.TotalItemsCount,
PageCount = posts.PageCount, };
Response.Headers.Add("X-Pagination", JsonConvert.SerializeObject(meta, new JsonSerializerSettings
{
ContractResolver = new CamelCasePropertyNamesContractResolver()
})); return Ok(postDto);
}
4、PostMan测试
三、生成前后页的URI
1、ConfiguraServices注册IUrlHelper,IActionContextAccessor
services.AddSingleton<IActionContextAccessor, ActionContextAccessor>();
services.AddScoped<IUrlHelper>(factory =>
{
var actionContext = factory.GetService<IActionContextAccessor>().ActionContext;
return new UrlHelper(actionContext);
});
2、Controller 编写方法返回URL
private string CreatePostUri(PostParameters parameters, PaginationResourceUriType uriType)
{
switch (uriType)
{
case PaginationResourceUriType.PreviousPage:
var previousParameters = new
{
pageIndex = parameters.PageIndex - ,
pageSize = parameters.PageSize,
orderBy = parameters.OrderBy,
fields = parameters.Fields
};
return _urlHelper.Link("GetPosts", previousParameters);
case PaginationResourceUriType.NextPage:
var nextParameters = new
{
pageIndex = parameters.PageIndex + ,
pageSize = parameters.PageSize,
orderBy = parameters.OrderBy,
fields = parameters.Fields
};
return _urlHelper.Link("GetPosts", nextParameters);
default:
var currentParameters = new
{
pageIndex = parameters.PageIndex,
pageSize = parameters.PageSize,
orderBy = parameters.OrderBy,
fields = parameters.Fields
};
return _urlHelper.Link("GetPosts", currentParameters);
}
}
[HttpGet(Name = "GetPosts")]
public async Task<IActionResult> Get(PostParameters parameters)
{
var posts = await _postRepository.GetPostsAsync(parameters);
var postDto=_mapper.Map<IEnumerable<Post>,IEnumerable<PostDTO>>(posts);
var previousPageLink = posts.HasPrevious ?
CreatePostUri(parameters, PaginationResourceUriType.PreviousPage) : null; var nextPageLink = posts.HasNext ?
CreatePostUri(parameters, PaginationResourceUriType.NextPage) : null;
var meta = new
{
PageSize = posts.PageSize,
PageIndex = posts.PageIndex,
TotalItemCount = posts.TotalItemsCount,
PageCount = posts.PageCount,
previousPageLink,
nextPageLink
};
Response.Headers.Add("X-Pagination", JsonConvert.SerializeObject(meta, new JsonSerializerSettings
{
ContractResolver = new CamelCasePropertyNamesContractResolver()
})); return Ok(postDto);
}
3、Postman测试
四、 过滤和搜索
过滤: 对集合资源附加一些条件, 筛选出结果.
1、 在PostParameters.cs类中，添加过滤字段；
public class PostParameters:QueryParameters
{
public string Title { get; set; }
}
2、修改 PostRepository.cs 中的方法：
public async Task<PaginatedList<Post>> GetPostsAsync(PostParameters parameters)
{ var Query = _myContext.Posts.AsQueryable();
if (!string.IsNullOrEmpty(parameters.Title))
{
var title = parameters.Title.ToLowerInvariant();
Query = Query.Where(x => x.Title.ToLowerInvariant()==title); } Query = Query.OrderBy(x => x.Id); var count = await Query.CountAsync();
var data = await Query.Skip(parameters.PageIndex * parameters.PageSize).Take(parameters.PageSize).ToListAsync();
return new PaginatedList<Post>(parameters.PageIndex, parameters.PageSize,count,data);
}
3、Postman测试
五、排序
- 翻页需要排序.
- 让资源按照资源的某个属性或多个属性进行正向或反向的排序.
- Resource Model的一个属性可能会映射到Entity Model的多个属性上
- Resource Model上的正序可能在Entity Model上就是倒序的
- 需要支持多属性的排序
- 复用
1、在 BlogDemo.Infrastructure nuget包 添加 System.Linq.Dynamic.Core
2、添加映射属性、属性映射、容器等类；
namespace BlogDemo.Infrastructure.Services
{
public class MappedProperty
{
public string Name { get; set; }
public bool Revert { get; set; }
}
}
public abstract class PropertyMapping<TSource, TDestination> : IPropertyMapping
where TDestination : IEntity
{
public Dictionary<string, List<MappedProperty>> MappingDictionary { get; } protected PropertyMapping(Dictionary<string, List<MappedProperty>> mappingDictionary)
{
MappingDictionary = mappingDictionary;
MappingDictionary[nameof(IEntity.Id)] = new List<MappedProperty>
{
new MappedProperty { Name = nameof(IEntity.Id), Revert = false}
};
}
}
namespace BlogDemo.Infrastructure.Services
{
public interface IPropertyMapping
{
Dictionary<string, List<MappedProperty>> MappingDictionary { get; }
}
}
namespace BlogDemo.Infrastructure.Services
{
public interface IPropertyMappingContainer
{
void Register<T>() where T : IPropertyMapping, new();
IPropertyMapping Resolve<TSource, TDestination>() where TDestination : IEntity;
bool ValidateMappingExistsFor<TSource, TDestination>(string fields) where TDestination : IEntity;
}
}
namespace BlogDemo.Infrastructure.Services
{
public class PropertyMappingContainer : IPropertyMappingContainer
{
protected internal readonly IList<IPropertyMapping> PropertyMappings = new List<IPropertyMapping>(); public void Register<T>() where T : IPropertyMapping, new()
{
if (PropertyMappings.All(x => x.GetType() != typeof(T)))
{
PropertyMappings.Add(new T());
}
} public IPropertyMapping Resolve<TSource, TDestination>() where TDestination : IEntity
{
var matchingMapping = PropertyMappings.OfType<PropertyMapping<TSource, TDestination>>().ToList();
if (matchingMapping.Count == )
{
return matchingMapping.First();
} throw new Exception($"Cannot find property mapping instance for <{typeof(TSource)},{typeof(TDestination)}");
} public bool ValidateMappingExistsFor<TSource, TDestination>(string fields) where TDestination : IEntity
{
var propertyMapping = Resolve<TSource, TDestination>(); if (string.IsNullOrWhiteSpace(fields))
{
return true;
} var fieldsAfterSplit = fields.Split(',');
foreach (var field in fieldsAfterSplit)
{
var trimmedField = field.Trim();
var indexOfFirstSpace = trimmedField.IndexOf(" ", StringComparison.Ordinal);
var propertyName = indexOfFirstSpace == - ? trimmedField : trimmedField.Remove(indexOfFirstSpace);
if (string.IsNullOrWhiteSpace(propertyName))
{
continue;
}
if (!propertyMapping.MappingDictionary.ContainsKey(propertyName))
{
return false;
}
}
return true;
}
}
}
namespace BlogDemo.Infrastructure.Extensions
{
public static class QueryableExtensions
{
public static IQueryable<T> ApplySort<T>(this IQueryable<T> source, string orderBy, IPropertyMapping propertyMapping)
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
} if (propertyMapping == null)
{
throw new ArgumentNullException(nameof(propertyMapping));
} var mappingDictionary = propertyMapping.MappingDictionary;
if (mappingDictionary == null)
{
throw new ArgumentNullException(nameof(mappingDictionary));
} if (string.IsNullOrWhiteSpace(orderBy))
{
return source;
} var orderByAfterSplit = orderBy.Split(',');
foreach (var orderByClause in orderByAfterSplit.Reverse())
{
var trimmedOrderByClause = orderByClause.Trim();
var orderDescending = trimmedOrderByClause.EndsWith(" desc");
var indexOfFirstSpace = trimmedOrderByClause.IndexOf(" ", StringComparison.Ordinal);
var propertyName = indexOfFirstSpace == - ?
trimmedOrderByClause : trimmedOrderByClause.Remove(indexOfFirstSpace);
if (string.IsNullOrEmpty(propertyName))
{
continue;
}
if (!mappingDictionary.TryGetValue(propertyName, out List<MappedProperty> mappedProperties))
{
throw new ArgumentException($"Key mapping for {propertyName} is missing");
}
if (mappedProperties == null)
{
throw new ArgumentNullException(propertyName);
}
mappedProperties.Reverse();
foreach (var destinationProperty in mappedProperties)
{
if (destinationProperty.Revert)
{
orderDescending = !orderDescending;
}
source = source.OrderBy(destinationProperty.Name + (orderDescending ? " descending" : " ascending"));
}
} return source;
} public static IQueryable<object> ToDynamicQueryable<TSource>
(this IQueryable<TSource> source, string fields, Dictionary<string, List<MappedProperty>> mappingDictionary)
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
} if (mappingDictionary == null)
{
throw new ArgumentNullException(nameof(mappingDictionary));
} if (string.IsNullOrWhiteSpace(fields))
{
return (IQueryable<object>)source;
} fields = fields.ToLower();
var fieldsAfterSplit = fields.Split(',').ToList();
if (!fieldsAfterSplit.Contains("id", StringComparer.InvariantCultureIgnoreCase))
{
fieldsAfterSplit.Add("id");
}
var selectClause = "new ("; foreach (var field in fieldsAfterSplit)
{
var propertyName = field.Trim();
if (string.IsNullOrEmpty(propertyName))
{
continue;
} var key = mappingDictionary.Keys.SingleOrDefault(k => String.CompareOrdinal(k.ToLower(), propertyName.ToLower()) == );
if (string.IsNullOrEmpty(key))
{
throw new ArgumentException($"Key mapping for {propertyName} is missing");
}
var mappedProperties = mappingDictionary[key];
if (mappedProperties == null)
{
throw new ArgumentNullException(key);
}
foreach (var destinationProperty in mappedProperties)
{
selectClause += $" {destinationProperty.Name},";
}
} selectClause = selectClause.Substring(, selectClause.Length - ) + ")";
return (IQueryable<object>)source.Select(selectClause);
} }
}
3、在ConfigureServices中注入
public void ConfigureServices(IServiceCollection services)
{ //排序
var propertyMappingContainer = new PropertyMappingContainer();
propertyMappingContainer.Register<PostPropertyMapping>();
services.AddSingleton<IPropertyMappingContainer>(propertyMappingContainer); }
4、修改 PostRepository.cs 中的方法：
public async Task<PaginatedList<Post>> GetPostsAsync(PostParameters parameters)
{ var Query = _myContext.Posts.AsQueryable();
if (!string.IsNullOrEmpty(parameters.Title))
{
var title = parameters.Title.ToLowerInvariant();
Query = Query.Where(x => x.Title.ToLowerInvariant()==title); }
Query = Query.ApplySort(parameters.OrderBy, _propertyMappingContainer.Resolve<PostDTO, Post>()); var count = await Query.CountAsync();
var data = await Query.Skip(parameters.PageIndex * parameters.PageSize).Take(parameters.PageSize).ToListAsync();
return new PaginatedList<Post>(parameters.PageIndex, parameters.PageSize,count,data);
}