[英]Custom Sorting using c# Linq Expressions
我正在尝试使C#Application和C#Web API更容易排序。 我正在使用Entity Framework Core进行持久性和测试。
在我的应用程序或Web API中,我确定了Order,Descending或Ascending,Property Name。
我将这些知识传递到我的存储库中,其中创建并执行了Linq查询。 问题是,当我有一个十进制列时,它执行字符串顺序而不是十进制顺序。
public static class SortingExtensions
{
public static IQueryable<T> SortBy<T>(
this IQueryable<T> queryable,
Sorting sorting)
{
IOrderedQueryable<T> orderedQueryable = null;
sorting.SortableEntities
.OrderBy(x => x.Order)
.ToList()
.ForEach(sortableEntity =>
{
Expression<Func<T, object>> expression = QueryHelper.GetDefaultSortExpression<T>(sortableEntity);
if (expression != null)
{
orderedQueryable = orderedQueryable == null
? queryable.OrderBy(expression, sortableEntity.Descending)
: orderedQueryable.OrderBy(expression, sortableEntity.Descending);
}
});
return orderedQueryable;
}
private static IOrderedQueryable<T> OrderBy<T, TKey>(
this IOrderedQueryable<T> query,
Expression<Func<T, TKey>> keySelector,
bool descending) => descending ? query.ThenByDescending(keySelector) : query.ThenBy(keySelector);
private static IOrderedQueryable<T> OrderBy<T, TKey>(
this IQueryable<T> query,
Expression<Func<T, TKey>> keySelector,
bool descending) => descending ? query.OrderByDescending(keySelector) : query.OrderBy(keySelector);
}
public static class QueryHelper
{
public static Expression<Func<T, object>> GetDefaultSortExpression<T>(SortableEntity sortableEntity)
{
Type entityType = typeof(T);
ParameterExpression arg = Expression.Parameter(entityType, "x");
string[] fieldNames = sortableEntity.Name.Split('.');
MemberExpression memberExpression = null;
foreach (string name in fieldNames)
{
Expression expressionToUse = memberExpression ?? (Expression) arg;
memberExpression = Expression.Property(expressionToUse, name.ToProperCase());
}
Expression propertyExpression = Expression.Convert(memberExpression, typeof(object));
Expression<Func<T, object>>
complexExpression = Expression.Lambda<Func<T, object>>(propertyExpression, arg);
return complexExpression;
}
}
public class SortableEntity
{
public int Order { get; set; }
public bool Descending { get; set; }
public string Name { get; set; }
}
public class Sorting
{
IEnumerable<SortableEntity> SortableEntities { get; }
}
public class TestDecimalPropertyClass : Entity
{
public TestDecimalPropertyClass(decimal @decimal) => Decimal = @decimal;
protected TestDecimalPropertyClass()
{
}
public decimal Decimal { get; set; }
}
public class TestDecimalPropertyClassRepository
{
private readonly DbContext _dbContext;
public TestDecimalPropertyClassRepository(DbContext dbContext)
{
_dbContext = dbContext;
}
public async Task<IEnumerable<TestDecimalPropertyClass>> GetAllAsync(Sorting sorting)
{
List<TestDecimalPropertyClass> entities = await _dbContext.Set<TestDecimalPropertyClass>()
.SortBy(sorting)
.ToListAsync();
return entities;
}
public async Task SaveAsync(TestDecimalPropertyClass testDecimalPropertyClass)
{
_dbContext.Set<TestDecimalPropertyClass>().Add(testDecimalPropertyClass);
await _dbContext.SaveChangesAsync();
}
}
这是我为它写的测试:
[TestFixture]
public class GenericSortingTests
{
private SqliteConnection SqliteConnection { get; set; }
[SetUp]
public void DbSetup()
{
SqliteConnectionStringBuilder sqliteConnectionStringBuilder = new SqliteConnectionStringBuilder
{
Mode = SqliteOpenMode.Memory,
Cache = SqliteCacheMode.Private
};
SqliteConnection = new SqliteConnection(sqliteConnectionStringBuilder.ToString());
SqliteConnection.Open();
}
[TearDown]
public void DbTearDown()
{
SqliteConnection.Close();
}
[Test]
public async Task GivenADecimalProperty_WhenISortByColumn_ThenItSorts()
{
decimal[] decimals = new[] {7m, 84.3m, 13.4m};
using (DbContext dbContext = GetDbContext())
{
TestDecimalPropertyClassRepository testRepository = new TestDecimalPropertyClassRepository(dbContext);
foreach (decimal @decimal in decimals)
{
TestDecimalPropertyClass entity = new TestDecimalPropertyClass(@decimal);
await testRepository.SaveAsync(entity);
}
}
IEnumerable<TestDecimalPropertyClass> entities;
using (DbContext dbContext = GetDbContext())
{
TestDecimalPropertyClassRepository testRepository = new TestDecimalPropertyClassRepository(dbContext);
entities = await testRepository.GetAllAsync(new Sorting
{
SortableEntities = new[]
{
new SortableEntity
{
Descending = false,
Name = "decimal",
Order = 0
}
}
});
}
List<TestDecimalPropertyClass> list = entities.ToList();
Assert.That(list.Count(), Is.EqualTo(decimals.Length));
Assert.That(list.ToArray()[0].Decimal, Is.EqualTo(7m));
Assert.That(list.ToArray()[1].Decimal, Is.EqualTo(13.4m));
Assert.That(list.ToArray()[2].Decimal, Is.EqualTo(84.3m));
}
private class TestDbContext : DbContext
{
public TestDbContext(DbContextOptions options) : base(options)
{
}
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<TestDecimalPropertyClass>();
base.OnModelCreating(modelBuilder);
}
}
private DbContext GetDbContext()
{
DbContextOptions<TestDbContext> options = new DbContextOptionsBuilder<TestDbContext>()
.UseSqlite(SqliteConnection)
.EnableSensitiveDataLogging()
.Options;
TestDbContext dbContext = new TestDbContext(options);
dbContext.Database.EnsureCreated();
return dbContext;
}
}
我希望它能按顺序对物品进行分类:7米,13.4米,84.3米,但它将其分为13.4米,7米,84.3米
任何人都可以帮助我理解为什么它这样做,所以我可以解决它?
谢谢,克里斯
首先,我以前曾试图像这样重新发明这种轮子,它永远不会像你想的那样真正起作用。 如果你需要那种动态的灵活性,那么可能已经有一个库在某处, 或者你也可以实际手动制作SQL或其他东西(它很糟糕,但有时它是唯一实用的方法)..除此之外.. 。
我认为你的问题实际上与SQLite有关 - 由于拼写错误或版本不相同,我无法让SQLite的东西工作(例如,SQLite的默认nuget包有一个SQLiteConnectionStringBuilder
而不是一个SqliteConnectionStringBuilder
,这不是' t似乎与你的例子具有相同的属性)所以我在某种程度上破解了你的代码以删除SQL的东西并摆脱异步的东西(因为我希望这真的不相关),所以我有这个存储库:
public class TestDecimalPropertyClassRepository
{
private readonly IList<TestDecimalPropertyClass> list;
public TestDecimalPropertyClassRepository(IEnumerable<TestDecimalPropertyClass> repo)
{
list = repo.ToList();
}
public IEnumerable<TestDecimalPropertyClass> GetAll(Sorting sorting)
{
List<TestDecimalPropertyClass> entities = list
.AsQueryable()
.SortBy(sorting)
.ToList();
return entities;
}
public void Save(TestDecimalPropertyClass testDecimalPropertyClass)
{
list.Add(testDecimalPropertyClass);
}
}
这使得测试看起来像这样
[Test]
public void GivenADecimalProperty_WhenISortByColumn_ThenItSorts()
{
decimal[] decimals = new[] { 7m, 84.3m, 13.4m };
var repo = decimals.Select(x => new TestDecimalPropertyClass(x));
TestDecimalPropertyClassRepository testRepository = new TestDecimalPropertyClassRepository(repo);
var entities = testRepository.GetAll(new Sorting
{
SortableEntities = new[]
{
new SortableEntity
{
Descending = false,
Name = "decimal",
Order = 0
}
}
});
List<TestDecimalPropertyClass> list = entities.ToList();
Assert.That(list.Count(), Is.EqualTo(decimals.Length));
Assert.That(list.ToArray()[0].Decimal, Is.EqualTo(7m));
Assert.That(list.ToArray()[1].Decimal, Is.EqualTo(13.4m));
Assert.That(list.ToArray()[2].Decimal, Is.EqualTo(84.3m));
}
并且所有扩展内容都保持不变,因此它仍然以相同的方式反射等。
这个测试通过很好。 现在,这并不是完全有效,因为它当然不再完全相同,但它确实意味着它可能不是框架错误解释小数属性的类型,或者与拳击相关的某种混乱/取消装箱意味着它无法计算出类型,并进行.ToString()进行比较。
假设SQLite EF提供程序正确地将其转换为SQL ORDER BY子句,您是否检查过此SQL? 在过去,我做过类似的事情(使用SQLite编写测试),并发现它不像SQL Server或类似的一些模糊方法那么完整。 也许提供者有一个bug,或者生成的表达式树中有一个怪癖,它不能很好地理解。
所以我先研究一下,而不是你写的代码。
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