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.
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.
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);
}
}
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