如何将GUID作为属性参数？

Question

我需要一些属性类中的Guid属性,如下所示:

public class SomeAttribute : Attribute {
    private Guid foreignIdentificator;
    public Guid ForeignIdentificator {
        get { return this.foreignIdentificator; }
        set { this.foreignIdentificator = value; }
    }
}

但是在属性定义中,我只能使用原始类型,它们是常量(我理解为什么,这让我有意义).解决方法可以将"ForeignIdentificator"定义为字符串,并在运行时创建Guid:

public class SomeAttribute : Attribute {
    private string foreignIdentificator;
    public string ForeignIdentificator {
        get { return this.foreignIdentificator; }
        set { this.foreignIdentificator = value; }
    }
    public Guid ForeignIdentificatorGuid {
        get { return new Guid( ForeignIdentificator ); }
    }
}

不幸的是,我没有检查类型安全性."ForeignIdentificator"属性可以包含任何字符串值,并且在创建过程中Guid将在运行时抛出异常,而不是在编译时抛出异常.

我知道编译器检查"System.Runtime.InteropServices.GuidAttribute"的字符串值是否为"Guid兼容性".这个检查正是我需要的,但我不知道这个检查是否在编译器中硬编码或者我可以明确定义(以及如何).

你知道某种方式,如何确保"Guid compatibilitybilty"检查属性？或者另一种方式,如何在属性中达到类型安全的Guid定义？谢谢.

Answer 1

我过去遇到了你的确切问题.我们只需要它们将GUID作为字符串传递...... VS GUID生成器工具将它提供给我们的默认方式(*F9168C5E-CEB2-4faa-B6BF-329BF39FA1E4).我们基本上做了你做的.我们在插件架构中使用它,因此我们的客户就是使用该界面的客户.如果你看看微软在需要做同样事情时所做的事情,他们就是这样做的.

这样做并不是一个问题.不是一次,我们是否已将此视为现场问题.

但是,您可能希望将该字符串字段命名为GUID,以免混淆您的使用者.添加一些文档,以防他们不知道需要什么格式.

当我看到这个时,我有同样的反应...但后来我继续前进,因为似乎没有类型安全的解决方案.

Answer 2

属性参数必须是常量。如果我违反了规则，我的C＃编译器会给出此错误：

属性参数必须是属性参数类型的常量表达式，typeof表达式或数组创建表达式

由于C＃中没有GUID文字，因此您必须以另一种格式（例如字符串）对GUID进行编码。但是，您还不完全了解：您可以使属性具有采用所需格式的ctor。这是一个与以下示例具有相同ctor的示例System.Guid：

[AttributeUsage(AttributeTargets.All, Inherited = false, AllowMultiple = true)]
sealed class MyGuidAttribute : Attribute
{
    public Guid Guid { get; private set; }

    //
    // Summary:
    //     Initializes a new instance of the System.Guid class using the specified array
    //     of bytes.
    //
    // Parameters:
    //   b:
    //     A 16 element byte array containing values with which to initialize the GUID.
    //
    // Exceptions:
    //   System.ArgumentNullException:
    //     b is null.
    //
    //   System.ArgumentException:
    //     b is not 16 bytes long.
    public MyGuidAttribute(byte[] b)
    {
        this.Guid = new Guid(b);
    }
    //
    // Summary:
    //     Initializes a new instance of the System.Guid class using the value represented
    //     by the specified string.
    //
    // Parameters:
    //   g:
    //     A System.String that contains a GUID in one of the following formats ('d'
    //     represents a hexadecimal digit whose case is ignored): 32 contiguous digits:
    //     dddddddddddddddddddddddddddddddd -or- Groups of 8, 4, 4, 4, and 12 digits
    //     with hyphens between the groups. The entire GUID can optionally be enclosed
    //     in matching braces or parentheses: dddddddd-dddd-dddd-dddd-dddddddddddd -or-
    //     {dddddddd-dddd-dddd-dddd-dddddddddddd} -or- (dddddddd-dddd-dddd-dddd-dddddddddddd)
    //     -or- Groups of 8, 4, and 4 digits, and a subset of eight groups of 2 digits,
    //     with each group prefixed by "0x" or "0X", and separated by commas. The entire
    //     GUID, as well as the subset, is enclosed in matching braces: {0xdddddddd,
    //     0xdddd, 0xdddd,{0xdd,0xdd,0xdd,0xdd,0xdd,0xdd,0xdd,0xdd}} All braces, commas,
    //     and "0x" prefixes are required. All embedded spaces are ignored. All leading
    //     zeroes in a group are ignored.  The digits shown in a group are the maximum
    //     number of meaningful digits that can appear in that group. You can specify
    //     from 1 to the number of digits shown for a group. The specified digits are
    //     assumed to be the low order digits of the group.
    //
    // Exceptions:
    //   System.ArgumentNullException:
    //     g is null.
    //
    //   System.FormatException:
    //     The format of g is invalid.
    //
    //   System.OverflowException:
    //     The format of g is invalid.
    public MyGuidAttribute(string g)
    {
        this.Guid = new Guid(g);
    }
    //
    // Summary:
    //     Initializes a new instance of the System.Guid class using the specified integers
    //     and byte array.
    //
    // Parameters:
    //   a:
    //     The first 4 bytes of the GUID.
    //
    //   b:
    //     The next 2 bytes of the GUID.
    //
    //   c:
    //     The next 2 bytes of the GUID.
    //
    //   d:
    //     The remaining 8 bytes of the GUID.
    //
    // Exceptions:
    //   System.ArgumentNullException:
    //     d is null.
    //
    //   System.ArgumentException:
    //     d is not 8 bytes long.
    public MyGuidAttribute(int a, short b, short c, byte[] d)
    {
        this.Guid = new Guid(a, b, c, d);
    }
    //
    // Summary:
    //     Initializes a new instance of the System.Guid class using the specified integers
    //     and bytes.
    //
    // Parameters:
    //   a:
    //     The first 4 bytes of the GUID.
    //
    //   b:
    //     The next 2 bytes of the GUID.
    //
    //   c:
    //     The next 2 bytes of the GUID.
    //
    //   d:
    //     The next byte of the GUID.
    //
    //   e:
    //     The next byte of the GUID.
    //
    //   f:
    //     The next byte of the GUID.
    //
    //   g:
    //     The next byte of the GUID.
    //
    //   h:
    //     The next byte of the GUID.
    //
    //   i:
    //     The next byte of the GUID.
    //
    //   j:
    //     The next byte of the GUID.
    //
    //   k:
    //     The next byte of the GUID.
    public MyGuidAttribute(int a, short b, short c, byte d, byte e, byte f, byte g, byte h, byte i, byte j, byte k)
    {
        this.Guid = new Guid(a, b, c, d, e, f, g, h, i, j, k);
    }
    //
    // Summary:
    //     Initializes a new instance of the System.Guid class using the specified unsigned
    //     integers and bytes.
    //
    // Parameters:
    //   a:
    //     The first 4 bytes of the GUID.
    //
    //   b:
    //     The next 2 bytes of the GUID.
    //
    //   c:
    //     The next 2 bytes of the GUID.
    //
    //   d:
    //     The next byte of the GUID.
    //
    //   e:
    //     The next byte of the GUID.
    //
    //   f:
    //     The next byte of the GUID.
    //
    //   g:
    //     The next byte of the GUID.
    //
    //   h:
    //     The next byte of the GUID.
    //
    //   i:
    //     The next byte of the GUID.
    //
    //   j:
    //     The next byte of the GUID.
    //
    //   k:
    //     The next byte of the GUID.
    [CLSCompliant(false)]
    public MyGuidAttribute(uint a, ushort b, ushort c, byte d, byte e, byte f, byte g, byte h, byte i, byte j, byte k)
    {
        this.Guid = new Guid(a, b, c, d, e, f, g, h, i, j, k);
    }
}