有可能让匿名类型实现接口吗?
我有一段代码，我想工作，但不知道如何做到这一点。
我已经得到了几个答案，要么说不，要么创建一个实现接口的类，构造它的新实例。这并不是很理想，但我想知道是否有一种机制可以在接口之上创建一个精简的动态类，从而使这变得简单。
public interface DummyInterface
{
string A { get; }
string B { get; }
}
public class DummySource
{
public string A { get; set; }
public string C { get; set; }
public string D { get; set; }
}
public class Test
{
public void WillThisWork()
{
var source = new DummySource[0];
var values = from value in source
select new
{
A = value.A,
B = value.C + "_" + value.D
};
DoSomethingWithDummyInterface(values);
}
public void DoSomethingWithDummyInterface(IEnumerable<DummyInterface> values)
{
foreach (var value in values)
{
Console.WriteLine("A = '{0}', B = '{1}'", value.A, value.B);
}
}
}
我发现一篇文章动态接口包装描述了一种方法。这是最好的方法吗?
最好的解决方案就是不要使用匿名类。
public class Test
{
class DummyInterfaceImplementor : IDummyInterface
{
public string A { get; set; }
public string B { get; set; }
}
public void WillThisWork()
{
var source = new DummySource[0];
var values = from value in source
select new DummyInterfaceImplementor()
{
A = value.A,
B = value.C + "_" + value.D
};
DoSomethingWithDummyInterface(values.Cast<IDummyInterface>());
}
public void DoSomethingWithDummyInterface(IEnumerable<IDummyInterface> values)
{
foreach (var value in values)
{
Console.WriteLine("A = '{0}', B = '{1}'", value.A, value.B);
}
}
}
注意，您需要将查询的结果强制转换为接口的类型。也许有更好的办法，但我找不到。
最好的解决方案就是不要使用匿名类。
public class Test
{
class DummyInterfaceImplementor : IDummyInterface
{
public string A { get; set; }
public string B { get; set; }
}
public void WillThisWork()
{
var source = new DummySource[0];
var values = from value in source
select new DummyInterfaceImplementor()
{
A = value.A,
B = value.C + "_" + value.D
};
DoSomethingWithDummyInterface(values.Cast<IDummyInterface>());
}
public void DoSomethingWithDummyInterface(IEnumerable<IDummyInterface> values)
{
foreach (var value in values)
{
Console.WriteLine("A = '{0}', B = '{1}'", value.A, value.B);
}
}
}
注意，您需要将查询的结果强制转换为接口的类型。也许有更好的办法，但我找不到。
使用Roslyn，您可以动态地创建一个继承自接口(或抽象类)的类。
我使用以下代码从抽象类创建具体类。
在本例中，AAnimal是一个抽象类。
var personClass = typeof(AAnimal).CreateSubclass("Person");
然后你可以实例化一些对象:
var person1 = Activator.CreateInstance(personClass);
var person2 = Activator.CreateInstance(personClass);
毫无疑问，这并不适用于所有情况，但这应该足以让你开始:
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;
namespace Publisher
{
public static class Extensions
{
public static Type CreateSubclass(this Type baseType, string newClassName, string newNamespace = "Magic")
{
//todo: handle ref, out etc.
var concreteMethods = baseType
.GetMethods()
.Where(method => method.IsAbstract)
.Select(method =>
{
var parameters = method
.GetParameters()
.Select(param => $"{param.ParameterType.FullName} {param.Name}")
.ToString(", ");
var returnTypeStr = method.ReturnParameter.ParameterType.Name;
if (returnTypeStr.Equals("Void")) returnTypeStr = "void";
var methodString = @$"
public override {returnTypeStr} {method.Name}({parameters})
{{
Console.WriteLine(""{newNamespace}.{newClassName}.{method.Name}() was called"");
}}";
return methodString.Trim();
})
.ToList();
var concreteMethodsString = concreteMethods
.ToString(Environment.NewLine + Environment.NewLine);
var classCode = @$"
using System;
namespace {newNamespace}
{{
public class {newClassName}: {baseType.FullName}
{{
public {newClassName}()
{{
}}
{concreteMethodsString}
}}
}}
".Trim();
classCode = FormatUsingRoslyn(classCode);
/*
var assemblies = new[]
{
MetadataReference.CreateFromFile(typeof(object).Assembly.Location),
MetadataReference.CreateFromFile(baseType.Assembly.Location),
};
*/
var assemblies = AppDomain
.CurrentDomain
.GetAssemblies()
.Where(a => !string.IsNullOrEmpty(a.Location))
.Select(a => MetadataReference.CreateFromFile(a.Location))
.ToArray();
var syntaxTree = CSharpSyntaxTree.ParseText(classCode);
var compilation = CSharpCompilation
.Create(newNamespace)
.AddSyntaxTrees(syntaxTree)
.AddReferences(assemblies)
.WithOptions(new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary));
using (var ms = new MemoryStream())
{
var result = compilation.Emit(ms);
//compilation.Emit($"C:\\Temp\\{newNamespace}.dll");
if (result.Success)
{
ms.Seek(0, SeekOrigin.Begin);
Assembly assembly = Assembly.Load(ms.ToArray());
var newTypeFullName = $"{newNamespace}.{newClassName}";
var type = assembly.GetType(newTypeFullName);
return type;
}
else
{
IEnumerable<Diagnostic> failures = result.Diagnostics.Where(diagnostic =>
diagnostic.IsWarningAsError ||
diagnostic.Severity == DiagnosticSeverity.Error);
foreach (Diagnostic diagnostic in failures)
{
Console.Error.WriteLine("{0}: {1}", diagnostic.Id, diagnostic.GetMessage());
}
return null;
}
}
}
public static string ToString(this IEnumerable<string> list, string separator)
{
string result = string.Join(separator, list);
return result;
}
public static string FormatUsingRoslyn(string csCode)
{
var tree = CSharpSyntaxTree.ParseText(csCode);
var root = tree.GetRoot().NormalizeWhitespace();
var result = root.ToFullString();
return result;
}
}
}
另一种选择是创建一个单独的、具体的实现类，在构造函数中接受lambdas。
public interface DummyInterface
{
string A { get; }
string B { get; }
}
// "Generic" implementing class
public class Dummy : DummyInterface
{
private readonly Func<string> _getA;
private readonly Func<string> _getB;
public Dummy(Func<string> getA, Func<string> getB)
{
_getA = getA;
_getB = getB;
}
public string A => _getA();
public string B => _getB();
}
public class DummySource
{
public string A { get; set; }
public string C { get; set; }
public string D { get; set; }
}
public class Test
{
public void WillThisWork()
{
var source = new DummySource[0];
var values = from value in source
select new Dummy // Syntax changes slightly
(
getA: () => value.A,
getB: () => value.C + "_" + value.D
);
DoSomethingWithDummyInterface(values);
}
public void DoSomethingWithDummyInterface(IEnumerable<DummyInterface> values)
{
foreach (var value in values)
{
Console.WriteLine("A = '{0}', B = '{1}'", value.A, value.B);
}
}
}
如果你所要做的只是将DummySource转换为DummyInterface，那么在构造函数中使用一个DummySource并实现接口的类会更简单。
但是，如果您需要将许多类型转换为DummyInterface，这就少了很多。
将匿名类型转换为接口是我一直想做的事情，但不幸的是，当前的实现迫使您拥有该接口的实现。
围绕它的最佳解决方案是使用某种类型的动态代理为您创建实现。利用优秀的林父项目你可以替代
select new
{
A = value.A,
B = value.C + "_" + value.D
};
with
select new DynamicObject(new
{
A = value.A,
B = value.C + "_" + value.D
}).CreateDuck<DummyInterface>();
