是否有可能有一个委托作为属性参数？ [英] Is it possible to have a delegate as attribute parameter?

问题描述

是否有可能有一个委托作为一个属性的参数？

Is it possible to have a delegate as the parameter of an attribute?

这样的：

public delegate IPropertySet ConnectionPropertiesDelegate();

public static class TestDelegate
{
    public static IPropertySet GetConnection()
    {
        return new PropertySetClass();
    }
}

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Interface,AllowMultiple=false,Inherited=true)]
public class WorkspaceAttribute : Attribute
{
    public ConnectionPropertiesDelegate ConnectionDelegate { get; set; }

    public WorkspaceAttribute(ConnectionPropertiesDelegate connectionDelegate)
    {
        ConnectionDelegate = connectionDelegate;
    }
}

[Workspace(TestDelegate.GetConnection)]
public class Test
{
}

和如果它不是可能的，什么是明智的选择吗？

And if its not possible, what are the sensible alternatives?

推荐答案

没有，你不能有一个委托作为属性构造函数的参数。见可用的类型：属性参数类型结果
作为一种变通方法（虽然它的哈克，而且容易出错），您可以创建具有反射一个委托：

No, you cannot have a delegate as an attribute constructor parameter. See available types: Attribute parameter types
As a workaround (although it's hacky and error prone) you can create a delegate with reflection:

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Interface, AllowMultiple = false, Inherited = true)]
public class WorkspaceAttribute : Attribute
{
    public ConnectionPropertiesDelegate ConnectionDelegate { get; set; }

    public WorkspaceAttribute(Type delegateType, string delegateName)
    {
         ConnectionDelegate = (ConnectionPropertiesDelegate)Delegate.CreateDelegate(delegateType, delegateType.GetMethod(delegateName));
    }
}

[Workspace(typeof(TestDelegate), "GetConnection")]
public class Test
{
}

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