我有一些示例代码可以简化我想要完成的任务。
OptionAttribute.cs
using System;
public class OptionAttribute : Attribute
{
public OptionAttribute(string option)
{
this.PickedOption = option;
}
public string PickedOption { get; private set; }
}
Options.cs
using System;
public class Options
{
public const string Cat = "CT";
public const string Dog = "DG";
public const string Monkey = "MNKY";
}
SomeClass.cs
using System;
[Option(Options.Dog)]
public class SomeClass
{
}
如何获取“SomeClass”类的“OptionAttribute”并获取“PickedOption”值?
更新
我不是在问如何使用反射。这是用于在保存包含代码的文件时生成代码。此时我没有更新的 dll,因此反射不起作用我正在尝试使用 Roslyn 来解析实际文件。 以下是我的尝试
string solutionPath = @"C:\Project\Project.sln";
var msWorkspace = MSBuildWorkspace.Create();
var solution = await msWorkspace.OpenSolutionAsync(solutionPath);
var project = solution.Projects.FirstOrDefault(p => p.Name == "Project1");
var compilation = await project.GetCompilationAsync();
var document = project.Documents.FirstOrDefault(d => d.Name == "Code.cs");
SyntaxTree syntaxTree = null;
document.TryGetSyntaxTree(out syntaxTree);
var semanticModel = compilation.GetSemanticModel(syntaxTree);
var commandCategoryAttribute = compilation.GetTypeByMetadataName("Project1.OptionAttribute");
var classDeclaration = syntaxTree.GetRoot().DescendantNodes().OfType<ClassDeclarationSyntax>().Skip(2).FirstOrDefault();
var classSymbol = semanticModel.GetDeclaredSymbol(classDeclaration);
var attrSymbol = classSymbol.GetAttributes().FirstOrDefault(a => a.AttributeClass.MetadataName == commandCategoryAttribute.MetadataName);
var attrSyntax = classDeclaration.AttributeLists.FirstOrDefault().Attributes.FirstOrDefault();
我的解决方案
我成功了!
public void Test()
{
string solutionPath = @"C:\Project\Project.sln";
var msWorkspace = MSBuildWorkspace.Create();
var solution = msWorkspace.OpenSolutionAsync(solutionPath).Result;
var project = solution.Projects.FirstOrDefault(p => p.Name == "Project1");
var compilation = project.GetCompilationAsync().Result;
var document = project.Documents.FirstOrDefault(d => d.Name == "SomeClass.cs");
SyntaxTree syntaxTree = null;
document.TryGetSyntaxTree(out syntaxTree);
SemanticModel semanticModel = compilation.GetSemanticModel(syntaxTree);
ClassDeclarationSyntax classDeclaration = syntaxTree.GetRoot().DescendantNodes().OfType<ClassDeclarationSyntax>().FirstOrDefault();
var attr = classDeclaration.AttributeLists.SelectMany(a => a.Attributes).FirstOrDefault(a => a.Name.ToString() == "Option");
var exp = attr.ArgumentList.Arguments.First().Expression;
string value = null;
var mem = exp as MemberAccessExpressionSyntax;
if (mem != null)
{
value = ResolveMemberAccess(mem, solution, compilation)?.ToString();
}
else
{
var lit = exp as LiteralExpressionSyntax;
if (lit != null)
{
value = semanticModel.GetConstantValue(lit).Value?.ToString();
}
}
}
public object ResolveMemberAccess(MemberAccessExpressionSyntax memberSyntax, Solution solution, Compilation compilation)
{
var model = compilation.GetSemanticModel(memberSyntax.SyntaxTree);
var memberSymbol = model.GetSymbolInfo(memberSyntax).Symbol;
var refs = SymbolFinder.FindReferencesAsync(memberSymbol, solution).Result.FirstOrDefault();
if (refs != null)
{
var defSyntax = refs.Definition.DeclaringSyntaxReferences.First();
var parent = compilation.GetSemanticModel(defSyntax.SyntaxTree);
var syn = defSyntax.GetSyntax();
var literal = syn.DescendantNodes().OfType<LiteralExpressionSyntax>().FirstOrDefault();
if (literal != null)
{
var val = parent.GetConstantValue(literal);
return val.Value;
}
else
{
var memberAccess = syn.DescendantNodes().OfType<MemberAccessExpressionSyntax>().FirstOrDefault();
if (memberAccess != null)
{
return ResolveMemberAccess(memberAccess, solution, compilation);
}
}
}
return null;
}
谢谢!
最佳答案
在我看来,您实际上非常接近。考虑将此添加到您的代码中:
attrSyntax.ArgumentList.Arguments.First().Expression.ToString()
这将整齐地返回
Options.Dog
所以你知道你有可用的信息。如果您将其稍微更改为例如:
var expression = attrSyntax.ArgumentList.Arguments.First().Expression as MemberAccessExpressionSyntax;
expression.Name.Identifier.ValueText.Dump();
你得到输出
Dog
但是,如果您想要它指向的实际值,您可以这样做:
var x = classDeclaration.AttributeLists.First().Attributes.First().ArgumentList.Arguments.First();
semanticModel.GetConstantValue(x.Expression).Value.Dump();
这将输出
DG
关于c# - 如何使用 Roslyn 获取编译时间常量值,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/35670115/