Is it possible to have a delegate as attribute parameter?(是否可以将委托作为属性参数?)

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问题描述

是否可以将委托作为属性的参数?

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

像这样:

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
{
}

如果不可能，有什么明智的选择?

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

推荐答案

不，您不能将委托作为属性构造函数参数.查看可用类型:属性参数类型
作为一种解决方法(尽管它很麻烦且容易出错)，您可以创建一个 带反射的委托:

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(typeof(ConnectionPropertiesDelegate), delegateType, delegateName);
    }
}

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

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