可靠地比较类型符号（ITypeSymbol）和Roslyn
我试图在以下情况下可靠地比较两个ITypeSymbol实例， ITypeSymbol是最简单也是最直接的方式（我在一个更大的项目中遇到了这些问题，并试图尽可能简化它）：
我用这个SyntaxTree得到了一个CSharpCompilation：
namespace MyAssembly
{
public class Foo
{
public Foo(Foo x)
{
}
}
}
我们用CSharpSyntaxRewriter遍历树，更改类并更新Compilation 。 在第一次运行中，我们记得第一个构造函数参数（在这种情况下是类本身的类型）的ITypeSymbol 。 更新编译之后，我们再次调用同一个重写器，并再次从构造函数参数中获取ITypeSymbol。 之后，我比较两个ITypeSymbols，我希望它们代表相同类型的MyAssembly.Foo 。
我的第一个比较方法是调用ITypeSymbol.Equals()方法，但它返回false 。 它基本上返回false因为我们改变了编译并在此期间得到了一个新的SemanticModel 。 如果我们不这样做，则Equals（）方法实际返回true。
比较DeclaringSyntaxReferences （这里还指出如何从罗斯林不同项目类型的符号（ITypeSymbol）比较？），因为我们改变了类返回false Foo在此期间本身。 如果构造函数参数的类型是Bar ，我们重写了Bar那么行为将是相同的。 要验证这一点，只需取消注释该行
//RewriteBar(rewriter, compilation, resultTree);
并用代码示例中的Bar替换构造函数参数类型。
结论： ITypeSymbol.Equals()不以新的编译和语义模型和工作比较DeclaringSyntaxReferences不与类型，我们在此期间改变了工作。 （我还测试了一种外部程序集的行为 - 在这种情况下，ITypeSymbol.Equals（）为我工作。）
所以我的问题是：
这是一个完整的测试程序，可以帮助我重现问题。 只需复制，包含Roslyn引用并执行：
using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.CSharp.Syntax;
namespace Demo.TypeSymbol
{
class Program
{
static void Main(string[] args)
{
var compilation = (CSharpCompilation) GetTestCompilation();
var rewriter = new Rewriter(changeSomething: true);
var tree = compilation.SyntaxTrees.First(); //first SyntaxTree is the one of class MyAssembly.Foo
rewriter.Model = compilation.GetSemanticModel (tree);
//first rewrite run
var resultTree = rewriter.Visit (tree.GetRoot()).SyntaxTree;
compilation = UpdateIfNecessary (compilation, rewriter, tree, resultTree);
rewriter.Model = compilation.GetSemanticModel (resultTree);
//just for demonstration; comment in to test behaviour when we are rewriting the class Bar -> in this case use Bar as constructor parameter in Foo
//RewriteBar(rewriter, compilation, resultTree);
//second rewrite run
rewriter.Visit (resultTree.GetRoot());
//now we want to compare the types...
Console.WriteLine(rewriter.ParameterTypeFirstRun);
Console.WriteLine(rewriter.ParameterTypeSecondRun);
//=> types are *not* equal
var typesAreEqual = rewriter.ParameterTypeFirstRun.Equals (rewriter.ParameterTypeSecondRun);
Console.WriteLine("typesAreEqual: " + typesAreEqual);
//=> syntax references are not equal
if(rewriter.ParameterTypeFirstRun.DeclaringSyntaxReferences.Any())
{
var syntaxReferencesAreEqual =
rewriter.ParameterTypeFirstRun.DeclaringSyntaxReferences.First()
.Equals(rewriter.ParameterTypeSecondRun.DeclaringSyntaxReferences.First());
Console.WriteLine("syntaxReferencesAreEqual: " + syntaxReferencesAreEqual);
}
//==> other options??
}
private static CSharpCompilation UpdateIfNecessary(CSharpCompilation compilation, Rewriter rewriter, SyntaxTree oldTree, SyntaxTree newTree)
{
if (oldTree != newTree)
{
//update compilation as the syntaxTree changed
compilation = compilation.ReplaceSyntaxTree(oldTree, newTree);
rewriter.Model = compilation.GetSemanticModel(newTree);
}
return compilation;
}
/// <summary>
/// rewrites the SyntaxTree of the class Bar, updates the compilation as well as the semantic model of the passed rewriter
/// </summary>
private static void RewriteBar(Rewriter rewriter, CSharpCompilation compilation, SyntaxTree firstSyntaxTree)
{
var otherRewriter = new Rewriter(true);
var otherTree = compilation.SyntaxTrees.Last();
otherRewriter.Model = compilation.GetSemanticModel(otherTree);
var otherResultTree = otherRewriter.Visit(otherTree.GetRoot()).SyntaxTree;
compilation = UpdateIfNecessary(compilation, otherRewriter, otherTree, otherResultTree);
rewriter.Model = compilation.GetSemanticModel(firstSyntaxTree);
}
public class Rewriter : CSharpSyntaxRewriter
{
public SemanticModel Model { get; set; }
private bool _firstRun = true;
private bool _changeSomething;
public ITypeSymbol ParameterTypeFirstRun { get; set; }
public ITypeSymbol ParameterTypeSecondRun { get; set; }
public Rewriter (bool changeSomething)
{
_changeSomething = changeSomething;
}
public override SyntaxNode VisitClassDeclaration(ClassDeclarationSyntax node)
{
node = (ClassDeclarationSyntax)base.VisitClassDeclaration(node);
//remember the types of the parameter
if (_firstRun)
ParameterTypeFirstRun = GetTypeSymbol (node);
else
ParameterTypeSecondRun = GetTypeSymbol (node);
_firstRun = false;
//change something and return updated node
if(_changeSomething)
node = node.WithMembers(node.Members.Add(GetMethod()));
return node;
}
/// <summary>
/// Gets the type of the first parameter of the first method
/// </summary>
private ITypeSymbol GetTypeSymbol(ClassDeclarationSyntax classDeclaration)
{
var members = classDeclaration.Members;
var methodSymbol = (IMethodSymbol) Model.GetDeclaredSymbol(members[0]);
return methodSymbol.Parameters[0].Type;
}
private MethodDeclarationSyntax GetMethod()
{
return (MethodDeclarationSyntax)
CSharpSyntaxTree.ParseText (@"public void SomeMethod(){ }").GetRoot().ChildNodes().First();
}
}
private static SyntaxTree[] GetTrees()
{
var treeList = new List<SyntaxTree>();
treeList.Add(CSharpSyntaxTree.ParseText(Source.Foo));
treeList.Add(CSharpSyntaxTree.ParseText(Source.Bar));
return treeList.ToArray();
}
private static Compilation GetTestCompilation()
{
var mscorlib = MetadataReference.CreateFromFile(typeof(object).Assembly.Location);
var refs = new List<PortableExecutableReference> { mscorlib };
// I used this to test it with a reference to an external assembly
// var testAssembly = MetadataReference.CreateFromFile(@"../../../Demo.TypeSymbol.TestAssembly/bin/Debug/Demo.TypeSymbol.TestAssembly.dll");
// refs.Add (testAssembly);
return CSharpCompilation.Create("dummyAssembly", GetTrees(), refs);
}
}
public static class Source
{
public static string Foo => @"
// for test with external assembly
//using Demo.TypeSymbol.TestAssembly;
namespace MyAssembly
{
public class Foo
{
public Foo(Foo x)
{
}
}
}
";
public static string Bar => @"
namespace MyAssembly
{
public class Bar
{
public Bar(int i)
{
}
}
}
";
}
}
一种可能性是调用SymbolFinder.FindSimilarSymbols，它会在您的新解决方案中为您提供符合名称和其他一些属性的符号。 从那里你可以在你的更新的编译中使用Equals。
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