如何在我的属性设置动态值

问题描述：

我想传递一个动态的变量作为参数传递给我的属性。在这里，我想用Environment.MachineName，请参见下面的code：

I would like to pass a dynamic variable as a parameter to my attribute. Here I want to use Environment.MachineName, see the code below:

public interface IMonitoringViewModelConfiguration : IConfigurationContainer
{
    [ConfigurationKey("MonitoringService", Environment.MachineName)]
    string ConnectionString { get; }
}

但是我得到这个错误：
错误1的属性参数必须是一个常量前pression，属性参数类型的typeof前pression或数组创建前pression Abc.ServiceBus.Monitoring.ViewModel

But I get this error: Error 1 An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type Abc.ServiceBus.Monitoring.ViewModel

有任何解决方法尽可能的干净，以通过我的Environment.MachineName？

Is there any workaround as clean as possible in order to pass my Environment.MachineName ?

感谢。

约翰

PS：我发现一些物件，说说这个情况，但它已被写入像两三年前。但今天，确实这是从.NET 4.0的CLR提供了一些很好的解决方案？

PS: I've found some articles which talk about this case but it have been written like 2-3 years ago. But today, does the clr which comes from .NET 4.0 gives some nice solution ?

答

您可以创建一个特殊值枚举，并在属性单独构造函数重载接受他们：

You could create an enum with special values, and accept them in a separate constructor overload in the attribute:

enum SpecialConfigurationValues
{
    MachineName
    // , other special ones
}

class ConfigurationKeyAttribute : Attribute
{
    private string _key;
    private string _value;

    public ConfigurationKeyAttribute(string key, string value)
    {
        // ...
    }

    public ConfigurationKeyAttribute(string key, SpecialConfigurationValues specialValue)
    {
        _key = key;
        switch (specialValue)
        {
            case SpecialConfigurationValues.MachineName:
                _value = Environment.MachineName;
                break;
            // case <other special ones>
        }
    }
}

[ConfigurationKey("MonitoringService", SpecialConfigurationValues.MachineName)]

如何在我的属性设置动态值

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