在Java中，Character类中有isJavaIdentifierStart和isJavaIdentifierPart方法，可用于判断字符串是否为有效的Java标识符，如下所示：C＃中是否有方法检查字符串是否是有效的标识符
public boolean isJavaIdentifier(String s) {
int n = s.length();
if (n==0) return false;
if (!Character.isJavaIdentifierStart(s.charAt(0)))
return false;
for (int i = 1; i < n; i++)
if (!Character.isJavaIdentifierPart(s.charAt(i)))
return false;
return true;
}
C＃有没有这样的东西？
基本上是这样的：
const string start = @"(\p{Lu}|\p{Ll}|\p{Lt}|\p{Lm}|\p{Lo}|\p{Nl})";
const string extend = @"(\p{Mn}|\p{Mc}|\p{Nd}|\p{Pc}|\p{Cf})";
Regex ident = new Regex(string.Format("{0}({0}|{1})*", start, extend));
s = s.Normalize();
return ident.IsMatch(s);
这可以通过使用反射来完成 - 见How to determine if a string is a valid variable name?
是：
// using System.CodeDom.Compiler;
CodeDomProvider provider = CodeDomProvider.CreateProvider("C#");
if (provider.IsValidIdentifier (YOUR_VARIABLE_NAME)) {
// Valid
} else {
// Not valid
}
这确实有一些性能。你应该意识到的含义。请参阅我的帖子了解更多信息。 – 2009-12-14 23:54:37
我会警惕这里提供的其他解决方案。调用CodeDomProvider.CreateProvider需要查找和解析Machine.Config文件以及app.config文件。这可能比检查字符串的时间要慢几倍。
相反，我会主张你做出以下更改之一：
缓存在一个静态变量的提供商。
这会导致您只创建一次，但会减慢类型加载。
通过创建一个Microsoft.CSharp.CSharpCodeProvider比如你的自我
这将跳过配置文件解析一起直接创建提供商。
编写代码来实现检查你自己。
如果你这样做，你可以最好地控制它的实现方式，如果你需要的话，它可以帮助你优化性能。有关C＃标识符的完整词汇语法，请参阅C# language spec的2.2.4节。
最近，我写了一个验证字符串作为一个合法的C＃标识符的扩展方法。
你可以找到这里的实施要点：https://gist.github.com/FabienDehopre/5245476
它基于标识符（http://msdn.microsoft.com/en-us/library/aa664670(v=vs.71).aspx）的MSDN文档上
public static bool IsValidIdentifier(this string identifier)
{
if (String.IsNullOrEmpty(identifier)) return false;
// C# keywords: http://msdn.microsoft.com/en-us/library/x53a06bb(v=vs.71).aspx
var keywords = new[]
{
"abstract", "event", "new", "struct",
"as", "explicit", "null", "switch",
"base", "extern", "object", "this",
"bool", "false", "operator", "throw",
"breal", "finally", "out", "true",
"byte", "fixed", "override", "try",
"case", "float", "params", "typeof",
"catch", "for", "private", "uint",
"char", "foreach", "protected", "ulong",
"checked", "goto", "public", "unchekeced",
"class", "if", "readonly", "unsafe",
"const", "implicit", "ref", "ushort",
"continue", "in", "return", "using",
"decimal", "int", "sbyte", "virtual",
"default", "interface", "sealed", "volatile",
"delegate", "internal", "short", "void",
"do", "is", "sizeof", "while",
"double", "lock", "stackalloc",
"else", "long", "static",
"enum", "namespace", "string"
};
// definition of a valid C# identifier: http://msdn.microsoft.com/en-us/library/aa664670(v=vs.71).aspx
const string formattingCharacter = @"\p{Cf}";
const string connectingCharacter = @"\p{Pc}";
const string decimalDigitCharacter = @"\p{Nd}";
const string combiningCharacter = @"\p{Mn}|\p{Mc}";
const string letterCharacter = @"\p{Lu}|\p{Ll}|\p{Lt}|\p{Lm}|\p{Lo}|\p{Nl}";
const string identifierPartCharacter = letterCharacter + "|" +
decimalDigitCharacter + "|" +
connectingCharacter + "|" +
combiningCharacter + "|" +
formattingCharacter;
const string identifierPartCharacters = "(" + identifierPartCharacter + ")+";
const string identifierStartCharacter = "(" + letterCharacter + "|_)";
const string identifierOrKeyword = identifierStartCharacter + "(" +
identifierPartCharacters + ")*";
var validIdentifierRegex = new Regex("^" + identifierOrKeyword + "$", RegexOptions.Compiled);
var normalizedIdentifier = identifier.Normalize();
// 1. check that the identifier match the validIdentifer regex and it's not a C# keyword
if (validIdentifierRegex.IsMatch(normalizedIdentifier) && !keywords.Contains(normalizedIdentifier))
{
return true;
}
// 2. check if the identifier starts with @
if (normalizedIdentifier.StartsWith("@") && validIdentifierRegex.IsMatch(normalizedIdentifier.Substring(1)))
{
return true;
}
// 3. it's not a valid identifier
return false;
}
这里Necromancing。
In。NET核心/ DNX，你可以用罗斯林 - SyntaxFacts做
Microsoft.CodeAnalysis.CSharp.SyntaxFacts.IsReservedKeyword(
Microsoft.CodeAnalysis.CSharp.SyntaxFacts.GetKeywordKind("protected")
);
foreach (ColumnDefinition cl in tableColumns)
{
sb.Append(@" public ");
sb.Append(cl.DOTNET_TYPE);
sb.Append(" ");
// for keywords
//if (!Microsoft.CodeAnalysis.CSharp.SyntaxFacts.IsValidIdentifier(cl.COLUMN_NAME))
if (Microsoft.CodeAnalysis.CSharp.SyntaxFacts.IsReservedKeyword(
Microsoft.CodeAnalysis.CSharp.SyntaxFacts.GetKeywordKind(cl.COLUMN_NAME)
))
sb.Append("@");
sb.Append(cl.COLUMN_NAME);
sb.Append("; // ");
sb.AppendLine(cl.SQL_TYPE);
} // Next cl
还是在旧的变体用的CodeDOM - 看看在单源代码后：
CodeDomProvider.cs
public virtual bool IsValidIdentifier (string value)
286 {
287 ICodeGenerator cg = CreateGenerator();
288 if (cg == null)
289 throw GetNotImplemented();
290 return cg.IsValidIdentifier (value);
291 }
292
然后CSharpCodeProvider.cs
public override ICodeGenerator CreateGenerator()
91 {
92 #if NET_2_0
93 if (providerOptions != null && providerOptions.Count > 0)
94 return new Mono.CSharp.CSharpCodeGenerator (providerOptions);
95 #endif
96 return new Mono.CSharp.CSharpCodeGenerator();
97 }
则C SharpCodeGenerator.cs
protected override bool IsValidIdentifier (string identifier)
{
if (identifier == null || identifier.Length == 0)
return false;
if (keywordsTable == null)
FillKeywordTable();
if (keywordsTable.Contains (identifier))
return false;
if (!is_identifier_start_character (identifier [0]))
return false;
for (int i = 1; i < identifier.Length; i ++)
if (! is_identifier_part_character (identifier [i]))
return false;
return true;
}
private static System.Collections.Hashtable keywordsTable;
private static string[] keywords = new string[] {
"abstract","event","new","struct","as","explicit","null","switch","base","extern",
"this","false","operator","throw","break","finally","out","true",
"fixed","override","try","case","params","typeof","catch","for",
"private","foreach","protected","checked","goto","public",
"unchecked","class","if","readonly","unsafe","const","implicit","ref",
"continue","in","return","using","virtual","default",
"interface","sealed","volatile","delegate","internal","do","is",
"sizeof","while","lock","stackalloc","else","static","enum",
"namespace",
"object","bool","byte","float","uint","char","ulong","ushort",
"decimal","int","sbyte","short","double","long","string","void",
"partial", "yield", "where"
};
static void FillKeywordTable()
{
lock (keywords) {
if (keywordsTable == null) {
keywordsTable = new Hashtable();
foreach (string keyword in keywords) {
keywordsTable.Add (keyword, keyword);
}
}
}
}
static bool is_identifier_start_character (char c)
{
return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_' || c == '@' || Char.IsLetter (c);
}
static bool is_identifier_part_character (char c)
{
return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_' || (c >= '0' && c <= '9') || Char.IsLetter (c);
}
你得到这个代码：
public static bool IsValidIdentifier (string identifier)
{
if (identifier == null || identifier.Length == 0)
return false;
if (keywordsTable == null)
FillKeywordTable();
if (keywordsTable.Contains(identifier))
return false;
if (!is_identifier_start_character(identifier[0]))
return false;
for (int i = 1; i < identifier.Length; i++)
if (!is_identifier_part_character(identifier[i]))
return false;
return true;
}
internal static bool is_identifier_start_character(char c)
{
return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_' || c == '@' || char.IsLetter(c);
}
internal static bool is_identifier_part_character(char c)
{
return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_' || (c >= '0' && c <= '9') || char.IsLetter(c);
}
private static System.Collections.Hashtable keywordsTable;
private static string[] keywords = new string[] {
"abstract","event","new","struct","as","explicit","null","switch","base","extern",
"this","false","operator","throw","break","finally","out","true",
"fixed","override","try","case","params","typeof","catch","for",
"private","foreach","protected","checked","goto","public",
"unchecked","class","if","readonly","unsafe","const","implicit","ref",
"continue","in","return","using","virtual","default",
"interface","sealed","volatile","delegate","internal","do","is",
"sizeof","while","lock","stackalloc","else","static","enum",
"namespace",
"object","bool","byte","float","uint","char","ulong","ushort",
"decimal","int","sbyte","short","double","long","string","void",
"partial", "yield", "where"
};
internal static void FillKeywordTable()
{
lock (keywords)
{
if (keywordsTable == null)
{
keywordsTable = new System.Collections.Hashtable();
foreach (string keyword in keywords)
{
keywordsTable.Add(keyword, keyword);
}
}
}
}
随着Roslyn是开源的，代码分析工具就在你的指尖，而且他们的表现写成。 （现在他们正在预发行）。
但是，我不能说加载程序集的性能成本。
使用的NuGet安装工具：
Install-Package Microsoft.CodeAnalysis -Pre
提出您的问题：
var isValid = Microsoft.CodeAnalysis.CSharp.SyntaxFacts.IsValidIdentifier("I'mNotValid");
Console.WriteLine(isValid); // False
的现在发布Roslyn项目提供Microsoft.CodeAnalysis.CSharp.SyntaxFacts，与SyntaxFacts.IsIdentifierStartCharacter(char)和SyntaxFacts.IsIdentifierPartCharacter(char)方法和Java一样。
这里使用的是一个简单的函数，我使用它将名词短语（例如“开始日期”）转换为C＃标识符（例如“StartDate”）。 N.B我使用Humanizer做驼峰大小写转换，Roslyn用来检查一个字符是否有效。
public static string Identifier(string name)
{
Check.IsNotNullOrWhitespace(name, nameof(name));
// trim off leading and trailing whitespace
name = name.Trim();
// should deal with spaces => camel casing;
name = name.Dehumanize();
var sb = new StringBuilder();
if (!SyntaxFacts.IsIdentifierStartCharacter(name[0]))
{
// the first characters
sb.Append("_");
}
foreach(var ch in name)
{
if (SyntaxFacts.IsIdentifierPartCharacter(ch))
{
sb.Append(ch);
}
}
var result = sb.ToString();
if (SyntaxFacts.GetKeywordKind(result) != SyntaxKind.None)
{
result = @"@" + result;
}
return result;
}
测试;
[TestCase("Start Date", "StartDate")]
[TestCase("Bad*chars", "BadChars")]
[TestCase(" leading ws", "LeadingWs")]
[TestCase("trailing ws ", "TrailingWs")]
[TestCase("class", "Class")]
[TestCase("int", "Int")]
[Test]
public void CSharp_GeneratesDecentIdentifiers(string input, string expected)
{
Assert.AreEqual(expected, CSharp.Identifier(input));
}
有用的事实，但没有帮助，你没有解释如何利用这个。我似乎找不到一个“Microsoft.CodeAnalysis”NuGet软件包，我似乎也找不到一个官方页面来解释可以在哪里获得该库。 – NightOwl888 2016-11-09 16:35:17
我在第一句中提供了链接：https：//github.com/dotnet/roslyn。它注意到：'nuget install Microsoft.CodeAnalysis＃安装语言API和服务' – 2016-11-12 20:37:52
您应该安装'Microsoft.CodeAnalysis.CSharp'来获得C＃规则。 – 2016-11-12 20:50:44
OMG 7 upvotes，它甚至不工作，甚至没有编译，直到我修复代码... – 2014-12-17 10:02:37