测试字符串是否为GUID而不抛出异常? [英] Test if string is a guid without throwing exceptions?

问题描述

我想尝试将字符串转换为Guid，但是我不想依靠捕获异常(

I want to try to convert a string to a Guid, but I don't want to rely on catching exceptions (

• 出于性能原因-异常代价高昂
• 出于可用性的原因-调试器弹出
• 出于设计原因-预期并非例外

换句话说，代码:

public static Boolean TryStrToGuid(String s, out Guid value)
{
    try
    {
        value = new Guid(s);
        return true;
    }
    catch (FormatException)
    {
        value = Guid.Empty;
        return false;
    }
}

不合适.

我会尝试使用RegEx，但是由于guid可以用括号括起来，用括号括起来，没有用括号括起来，所以很难.

I would try using RegEx, but since the guid can be parenthesis wrapped, brace wrapped, none wrapped, makes it hard.

此外，我还认为某些Guid值无效(?)

Additionally, I thought certain Guid values are invalid(?)

更新1

ChristianK 有一个只捕获FormatException，而不捕获全部的好主意.更改了问题的代码示例以包含建议.

ChristianK had a good idea to catch only FormatException, rather than all. Changed the question's code sample to include suggestion.

更新2

为什么要担心引发异常?我真的经常会遇到无效的GUID吗?

Why worry about thrown exceptions? Am I really expecting invalid GUIDs all that often?

答案是是.这就是为什么我使用TryStrToGuid的原因-我我期望有坏数据.

The answer is yes. That is why I am using TryStrToGuid - I am expecting bad data.

示例1 命名空间扩展可以通过将GUID附加到文件夹名称来指定.我可能正在解析文件夹名称，检查最后.之后的文本是否是GUID.

Example 1 Namespace extensions can be specified by appending a GUID to a folder name. I might be parsing folder names, checking to see if the text after the final . is a GUID.

c:\Program Files
c:\Program Files.old
c:\Users
c:\Users.old
c:\UserManager.{CE7F5AA5-6832-43FE-BAE1-80D14CD8F666}
c:\Windows
c:\Windows.old

示例2 我可能正在运行一个使用率很高的Web服务器，希望检查某些回发数据的有效性.我不希望无效数据占用资源比需要多2-3个数量级.

Example 2 I might be running a heavily used web-server wants to check the validity of some posted back data. I don't want invalid data tying up resources 2-3 orders of magnitude higher than it needs to be.

示例3 ，我可能正在解析用户输入的搜索表达式.

Example 3 I might be parsing a search expression entered by a user.

如果他们输入GUID，我想对其进行特殊处理(例如，专门搜索该对象，或在响应文本中突出显示并格式化该特定搜索词.)

If they enter GUID's I want to process them specially (such as specifically searching for that object, or highlight and format that specific search term in the response text.)

更新3-性能基准

测试转换10,000个好向导和10,000个坏向导.

Test converting 10,000 good Guids, and 10,000 bad Guids.

Catch FormatException:
   10,000 good:     63,668 ticks
   10,000 bad:   6,435,609 ticks

Regex Pre-Screen with try-catch:
   10,000 good:    637,633 ticks
   10,000 bad:     717,894 ticks

COM Interop CLSIDFromString
   10,000 good:    126,120 ticks
   10,000 bad:      23,134 ticks

p.s.我不必证明一个问题.

推荐答案

性能基准

Catch exception:
   10,000 good:    63,668 ticks
   10,000 bad:  6,435,609 ticks

Regex Pre-Screen:
   10,000 good:   637,633 ticks
   10,000 bad:    717,894 ticks

COM Interop CLSIDFromString
   10,000 good:   126,120 ticks
   10,000 bad:     23,134 ticks

COM Intertop(最快)答案:

/// <summary>
/// Attempts to convert a string to a guid.
/// </summary>
/// <param name="s">The string to try to convert</param>
/// <param name="value">Upon return will contain the Guid</param>
/// <returns>Returns true if successful, otherwise false</returns>
public static Boolean TryStrToGuid(String s, out Guid value)
{
   //ClsidFromString returns the empty guid for null strings   
   if ((s == null) || (s == ""))   
   {      
      value = Guid.Empty;      
      return false;   
   }

   int hresult = PInvoke.ObjBase.CLSIDFromString(s, out value);
   if (hresult >= 0)
   {
      return true;
   }
   else
   {
      value = Guid.Empty;
      return false;
   }
}


namespace PInvoke
{
    class ObjBase
    {
        /// <summary>
        /// This function converts a string generated by the StringFromCLSID function back into the original class identifier.
        /// </summary>
        /// <param name="sz">String that represents the class identifier</param>
        /// <param name="clsid">On return will contain the class identifier</param>
        /// <returns>
        /// Positive or zero if class identifier was obtained successfully
        /// Negative if the call failed
        /// </returns>
        [DllImport("ole32.dll", CharSet = CharSet.Unicode, ExactSpelling = true, PreserveSig = true)]
        public static extern int CLSIDFromString(string sz, out Guid clsid);
    }
}

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底线:如果需要检查字符串是否为Guid，并且在意性能，请使用COM Interop.

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Bottom line: If you need to check if a string is a guid, and you care about performance, use COM Interop.

如果您需要将String表示形式的guid转换为Guid，请使用

If you need to convert a guid in String representation to a Guid, use

new Guid(someString);

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