[英]Can we use c# indexer to index class properties?
我想像數組一樣索引 class 屬性。
Public class Foo
{
propery p1{get;set;}
propery p3{get;set;}
propery p3{get;set;}
.
.
.
.
}
我想像數組 FOO.p1=Value 一樣索引每個屬性
Foo[0]=Value(索引0指的是p1)
我對數據庫不太了解,那里可能有現成的解決方案。 但至少你可以通過這種方式反思來做到這一點:
using System.Reflection;
[AttributeUsage(AttributeTargets.Property, Inherited = true, AllowMultiple = false)]
public sealed class IndexedPropertyAttribute : Attribute
{
readonly int index;
public IndexedPropertyAttribute(int index)
{
this.index = index;
}
public int Index
{
get { return index; }
}
}
public abstract class WithIndexedProperties
{
private Lazy<IReadOnlyDictionary<int, PropertyInfo>> properties;
protected WithIndexedProperties()
{
properties = new Lazy<IReadOnlyDictionary<int, PropertyInfo>>(
() => {
var linq = from prop in this.GetType().GetProperties()
let attr = prop.GetCustomAttributes(typeof(IndexedPropertyAttribute), true)
where attr.Length is 1
select (((IndexedPropertyAttribute)attr[0]).Index, prop);
return linq.ToDictionary(p => p.Index, p => p.prop);
});
}
public object? this[int propertyIndex]
{
get
{
return properties.Value[propertyIndex].GetValue(this);
}
set
{
properties.Value[propertyIndex].SetValue(this, value);
}
}
}
還有一個例子:
Clss obj = new Clss();
obj[0] = "ABC";
obj[2] = 222;
obj[4] = 444;
// Here obj.A will be "ABC", obj.B will be 444 and obj.C will be 222.
public class Clss : WithIndexedProperties
{
[IndexedProperty(0)]
public string? A { get; init; }
[IndexedProperty(4)]
public int B { get; init; }
[IndexedProperty(2)]
public int C { get; init; }
}
我認為你需要做這樣的事情。 下面的代碼是針對您的問題的非常通用的解決方案,我可能需要為您自己進行一些定制
using System.Reflection;
public class ReflectionBasedIndexedType
{
public int A1 { get; set; } = 10;
public int A2 { get; set; } = 20;
public string SomeString => "Hello There";
private readonly Dictionary<string, object> _underlyingCollection;
public object this[string name] => _underlyingCollection[name];
public ReflectionBasedIndexedType()
{
_underlyingCollection = GetUnderlyingCollection();
}
private Dictionary<string, object> GetUnderlyingCollection()
{
Dictionary<string, object> container = new();
// get the properties defined in the class, I am filtering
// with constraint that, I want get only public and class level
// Properties, which means I won't get any private/protected or
// static properties if there is defined such in the class
// also where filters out indexer property, which we have defined
// inside this class, without this line, there will be exception
IEnumerable<PropertyInfo> properties = GetType()
.GetProperties(BindingFlags.Instance | BindingFlags.Public)
.Where(x => x.GetIndexParameters().Length == 0);
foreach (PropertyInfo property in properties)
{
container.Add(property.Name, property.GetValue(this)!);
}
return container;
}
}
而且用例將是這樣的
ReflectionBasedIndexedType rbit = new();
var a1 = rbit[nameof(rbit.A1)];
var a2 = rbit[nameof(rbit.A2)];
var str = rbit[nameof(rbit.SomeString)];
Console.WriteLine(a1);
Console.WriteLine(a2);
Console.WriteLine(str);
控制台中的 output 就是這個
10
20
Hello There
我認為你至少有兩種方法。 第一個,是@Swapper提到的,你可以使用反射。 這樣,class就正常了,你必須在你想使用class的地方寫你的擁抱代碼。第二種方式更簡單,但有點模糊。 您可以使用dynamic
類型。 如果您知道如何使用它,那沒關系。 否則請告訴我,然后我將為您創建示例代碼。
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