.NET Decompiler with support for PDB generation, ReadyToRun, Metadata (&more) - cross-platform!
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// Copyright (c) 2026 AlphaSierraPapa for the SharpDevelop Team
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
using System;
using System.Collections.Generic;
using System.Composition;
using System.IO;
using System.Linq;
using System.Reflection.Metadata;
using System.Reflection.PortableExecutable;
using AvaloniaEdit.Highlighting;
using ICSharpCode.Decompiler;
using ICSharpCode.Decompiler.CSharp;
using ICSharpCode.Decompiler.CSharp.OutputVisitor;
using ICSharpCode.Decompiler.CSharp.ProjectDecompiler;
using ICSharpCode.Decompiler.CSharp.Syntax;
using ICSharpCode.Decompiler.CSharp.Transforms;
using ICSharpCode.Decompiler.IL;
using ICSharpCode.Decompiler.Metadata;
using ICSharpCode.Decompiler.Output;
using ICSharpCode.Decompiler.Solution;
using ICSharpCode.Decompiler.TypeSystem;
using ICSharpCode.ILSpy.Properties;
using ICSharpCode.ILSpyX;
using ConversionFlags = ICSharpCode.Decompiler.Output.ConversionFlags;
// Two unrelated `LanguageVersion` types are in scope: a DTO in ILSpyX (toolbar dropdown
// items) and an enum in Decompiler.CSharp (the version key the decompiler reads). Alias
// the enum to disambiguate; the DTO keeps its plain name to match WPF's call sites.
using CSharpLanguageVersion = ICSharpCode.Decompiler.CSharp.LanguageVersion;
using LanguageVersionDto = ICSharpCode.ILSpyX.LanguageVersion;
namespace ILSpy.Languages
{
[Export(typeof(Language))]
[Shared]
public sealed class CSharpLanguage : Language
{
public override string Name => "C#";
public override string FileExtension => ".cs";
public override string ProjectFileExtension => ".csproj";
static IReadOnlyList<LanguageVersionDto>? cachedVersions;
public override IReadOnlyList<LanguageVersionDto> LanguageVersions => cachedVersions ??= new List<LanguageVersionDto> {
new(CSharpLanguageVersion.CSharp1.ToString(), "C# 1.0 / VS .NET"),
new(CSharpLanguageVersion.CSharp2.ToString(), "C# 2.0 / VS 2005"),
new(CSharpLanguageVersion.CSharp3.ToString(), "C# 3.0 / VS 2008"),
new(CSharpLanguageVersion.CSharp4.ToString(), "C# 4.0 / VS 2010"),
new(CSharpLanguageVersion.CSharp5.ToString(), "C# 5.0 / VS 2012"),
new(CSharpLanguageVersion.CSharp6.ToString(), "C# 6.0 / VS 2015"),
new(CSharpLanguageVersion.CSharp7.ToString(), "C# 7.0 / VS 2017"),
new(CSharpLanguageVersion.CSharp7_1.ToString(), "C# 7.1 / VS 2017.3"),
new(CSharpLanguageVersion.CSharp7_2.ToString(), "C# 7.2 / VS 2017.4"),
new(CSharpLanguageVersion.CSharp7_3.ToString(), "C# 7.3 / VS 2017.7"),
new(CSharpLanguageVersion.CSharp8_0.ToString(), "C# 8.0 / VS 2019"),
new(CSharpLanguageVersion.CSharp9_0.ToString(), "C# 9.0 / VS 2019.8"),
new(CSharpLanguageVersion.CSharp10_0.ToString(), "C# 10.0 / VS 2022"),
new(CSharpLanguageVersion.CSharp11_0.ToString(), "C# 11.0 / VS 2022.4"),
new(CSharpLanguageVersion.CSharp12_0.ToString(), "C# 12.0 / VS 2022.8"),
new(CSharpLanguageVersion.CSharp13_0.ToString(), "C# 13.0 / VS 2022.12"),
new(CSharpLanguageVersion.CSharp14_0.ToString(), "C# 14.0 / VS 2026"),
};
static CSharpAmbience CreateAmbience() => new() {
ConversionFlags = ConversionFlags.ShowTypeParameterList | ConversionFlags.PlaceReturnTypeAfterParameterList,
};
public override string TypeToString(IType type, ConversionFlags conversionFlags = ConversionFlags.UseFullyQualifiedEntityNames | ConversionFlags.UseFullyQualifiedTypeNames)
{
ArgumentNullException.ThrowIfNull(type);
var ambience = CreateAmbience();
ambience.ConversionFlags |= conversionFlags;
return type is ITypeDefinition def
? ambience.ConvertSymbol(def)
: ambience.ConvertType(type);
}
public override string EntityToString(IEntity entity, ConversionFlags conversionFlags)
{
ArgumentNullException.ThrowIfNull(entity);
var ambience = CreateAmbience();
ambience.ConversionFlags |= conversionFlags
| ConversionFlags.ShowReturnType
| ConversionFlags.ShowParameterList
| ConversionFlags.ShowParameterModifiers;
return ambience.ConvertSymbol(entity);
}
public override void WriteCommentLine(ITextOutput output, string comment) => output.WriteLine("// " + comment);
public override bool ShowMember(IEntity member)
{
ArgumentNullException.ThrowIfNull(member);
if (member.MetadataToken.IsNil)
return true;
var assembly = member.ParentModule?.MetadataFile;
if (assembly == null)
return true;
return !CSharpDecompiler.MemberIsHidden(assembly, member.MetadataToken, new DecompilerSettings());
}
public override RichText GetRichTextTooltip(IEntity entity)
{
ArgumentNullException.ThrowIfNull(entity);
var flags = ConversionFlags.All & ~(ConversionFlags.ShowBody | ConversionFlags.PlaceReturnTypeAfterParameterList);
var output = new StringWriter();
var decoratedWriter = new TextWriterTokenWriter(output);
var writer = new CSharpHighlightingTokenWriter(TokenWriter.InsertRequiredSpaces(decoratedWriter), locatable: decoratedWriter);
if (entity is IMethod m && m.IsLocalFunction)
writer.WriteIdentifier(Identifier.Create("(local)"));
new CSharpAmbience { ConversionFlags = flags }.ConvertSymbol(entity, writer, FormattingOptionsFactory.CreateAllman());
return new RichText(output.ToString(), writer.HighlightingModel);
}
CSharpDecompiler CreateDecompiler(MetadataFile module, DecompilationOptions options)
{
var decompiler = new CSharpDecompiler(module, module.GetAssemblyResolver(options.DecompilerSettings.AutoLoadAssemblyReferences), options.DecompilerSettings) {
CancellationToken = options.CancellationToken,
DebugInfoProvider = module.GetDebugInfoOrNull(),
};
if (options.EscapeInvalidIdentifiers)
decompiler.AstTransforms.Add(new EscapeInvalidIdentifiers());
return decompiler;
}
public override void DecompileMethod(IMethod method, ITextOutput output, DecompilationOptions options)
{
MetadataFile assembly = method.ParentModule!.MetadataFile!;
CSharpDecompiler decompiler = CreateDecompiler(assembly, options);
AddReferenceAssemblyWarningMessage(assembly, output);
AddReferenceWarningMessage(assembly, output);
WriteCommentLine(output, assembly.FullName);
WriteCommentLine(output, TypeToString(method.DeclaringType));
var methodDefinition = decompiler.TypeSystem.MainModule.ResolveEntity(method.MetadataToken) as IMethod;
if (methodDefinition!.IsConstructor && methodDefinition.DeclaringType.IsReferenceType != false)
{
var members = CollectFieldsAndCtors(methodDefinition.DeclaringTypeDefinition!, methodDefinition.IsStatic);
decompiler.AstTransforms.Add(new SelectCtorTransform(methodDefinition));
WriteCode(output, options.DecompilerSettings, decompiler.Decompile(members), decompiler.TypeSystem);
}
else
{
WriteCode(output, options.DecompilerSettings, decompiler.Decompile(method.MetadataToken), decompiler.TypeSystem);
}
}
public override void DecompileProperty(IProperty property, ITextOutput output, DecompilationOptions options)
{
MetadataFile assembly = property.ParentModule!.MetadataFile!;
CSharpDecompiler decompiler = CreateDecompiler(assembly, options);
AddReferenceAssemblyWarningMessage(assembly, output);
AddReferenceWarningMessage(assembly, output);
WriteCommentLine(output, assembly.FullName);
WriteCommentLine(output, TypeToString(property.DeclaringType));
WriteCode(output, options.DecompilerSettings, decompiler.Decompile(property.MetadataToken), decompiler.TypeSystem);
}
public override void DecompileField(IField field, ITextOutput output, DecompilationOptions options)
{
MetadataFile assembly = field.ParentModule!.MetadataFile!;
CSharpDecompiler decompiler = CreateDecompiler(assembly, options);
AddReferenceAssemblyWarningMessage(assembly, output);
AddReferenceWarningMessage(assembly, output);
WriteCommentLine(output, assembly.FullName);
WriteCommentLine(output, TypeToString(field.DeclaringType));
if (field.IsConst)
{
WriteCode(output, options.DecompilerSettings, decompiler.Decompile(field.MetadataToken), decompiler.TypeSystem);
}
else
{
var members = CollectFieldsAndCtors(field.DeclaringTypeDefinition!, field.IsStatic);
var resolvedField = decompiler.TypeSystem.MainModule.GetDefinition((FieldDefinitionHandle)field.MetadataToken);
decompiler.AstTransforms.Add(new SelectFieldTransform(resolvedField));
WriteCode(output, options.DecompilerSettings, decompiler.Decompile(members), decompiler.TypeSystem);
}
}
public override void DecompileEvent(IEvent ev, ITextOutput output, DecompilationOptions options)
{
MetadataFile assembly = ev.ParentModule!.MetadataFile!;
CSharpDecompiler decompiler = CreateDecompiler(assembly, options);
AddReferenceAssemblyWarningMessage(assembly, output);
AddReferenceWarningMessage(assembly, output);
WriteCommentLine(output, assembly.FullName);
WriteCommentLine(output, TypeToString(ev.DeclaringType));
WriteCode(output, options.DecompilerSettings, decompiler.Decompile(ev.MetadataToken), decompiler.TypeSystem);
}
public override void DecompileType(ITypeDefinition type, ITextOutput output, DecompilationOptions options)
{
MetadataFile assembly = type.ParentModule!.MetadataFile!;
CSharpDecompiler decompiler = CreateDecompiler(assembly, options);
AddReferenceAssemblyWarningMessage(assembly, output);
AddReferenceWarningMessage(assembly, output);
WriteCommentLine(output, assembly.FullName);
WriteCommentLine(output, TypeToString(type, ConversionFlags.UseFullyQualifiedTypeNames | ConversionFlags.UseFullyQualifiedEntityNames));
WriteCode(output, options.DecompilerSettings, decompiler.Decompile(type.MetadataToken), decompiler.TypeSystem);
}
public override void DecompileNamespace(string nameSpace, IEnumerable<ITypeDefinition> types, ITextOutput output, DecompilationOptions options)
{
var typesByModule = types.GroupBy(t => t.ParentModule!.MetadataFile);
bool first = true;
foreach (var group in typesByModule)
{
if (!first)
output.WriteLine();
first = false;
MetadataFile assembly = group.Key!;
CSharpDecompiler decompiler = CreateDecompiler(assembly, options);
AddReferenceAssemblyWarningMessage(assembly, output);
AddReferenceWarningMessage(assembly, output);
WriteCommentLine(output, assembly.FullName);
WriteCommentLine(output, nameSpace);
WriteCode(output, options.DecompilerSettings, decompiler.Decompile(group.Select(t => t.MetadataToken)), decompiler.TypeSystem);
}
}
public override ProjectId? DecompileAssembly(LoadedAssembly assembly, ITextOutput output, DecompilationOptions options)
{
var module = assembly.GetMetadataFileOrNull();
if (module == null)
return null;
if (options.FullDecompilation && options.SaveAsProjectDirectory != null)
return DecompileAsProject(assembly, module, output, options);
AddReferenceAssemblyWarningMessage(module, output);
AddReferenceWarningMessage(module, output);
output.WriteLine();
base.DecompileAssembly(assembly, output, options);
var assemblyResolver = assembly.GetAssemblyResolver(loadOnDemand: options.FullDecompilation && options.DecompilerSettings.AutoLoadAssemblyReferences);
var typeSystem = new DecompilerTypeSystem(module, assemblyResolver, options.DecompilerSettings);
var globalType = typeSystem.MainModule.TypeDefinitions.FirstOrDefault();
if (globalType != null)
{
output.Write("// Global type: ");
output.WriteReference(globalType, ILAmbience.EscapeName(globalType.FullName));
output.WriteLine();
}
var metadata = module.Metadata;
var corHeader = module.CorHeader;
if (module is PEFile peFile && corHeader != null)
{
var entrypointHandle = MetadataTokenHelpers.EntityHandleOrNil(corHeader.EntryPointTokenOrRelativeVirtualAddress);
if (!entrypointHandle.IsNil && entrypointHandle.Kind == HandleKind.MethodDefinition)
{
var entrypoint = typeSystem.MainModule.ResolveMethod(entrypointHandle, new GenericContext());
if (entrypoint != null)
{
output.Write("// Entry point: ");
output.WriteReference(entrypoint, ILAmbience.EscapeName(entrypoint.DeclaringType.FullName + "." + entrypoint.Name));
output.WriteLine();
}
}
output.WriteLine("// Architecture: " + GetPlatformDisplayName(peFile));
if ((corHeader.Flags & CorFlags.ILOnly) == 0)
output.WriteLine("// This assembly contains unmanaged code.");
string runtimeName = GetRuntimeDisplayName(module);
if (runtimeName != null)
output.WriteLine("// Runtime: " + runtimeName);
if ((corHeader.Flags & CorFlags.StrongNameSigned) != 0)
output.WriteLine("// This assembly is signed with a strong name key.");
if (peFile.Reader.ReadDebugDirectory().Any(d => d.Type == DebugDirectoryEntryType.Reproducible))
output.WriteLine("// This assembly was compiled using the /deterministic option.");
if (module.Metadata.MetadataKind != MetadataKind.Ecma335)
output.WriteLine("// This assembly was loaded with Windows Runtime projections applied.");
}
else
{
string runtimeName = GetRuntimeDisplayName(module);
if (runtimeName != null)
output.WriteLine("// Runtime: " + runtimeName);
}
if (metadata.IsAssembly)
{
var asm = metadata.GetAssemblyDefinition();
if (asm.HashAlgorithm != System.Reflection.AssemblyHashAlgorithm.None)
output.WriteLine("// Hash algorithm: " + asm.HashAlgorithm.ToString().ToUpper());
if (!asm.PublicKey.IsNil)
{
output.Write("// Public key: ");
var reader = metadata.GetBlobReader(asm.PublicKey);
while (reader.RemainingBytes > 0)
output.Write(reader.ReadByte().ToString("x2"));
output.WriteLine();
}
}
var debugInfo = assembly.GetDebugInfoOrNull();
if (debugInfo != null)
output.WriteLine("// Debug info: " + debugInfo.Description);
output.WriteLine();
var decompiler = new CSharpDecompiler(typeSystem, options.DecompilerSettings) {
CancellationToken = options.CancellationToken,
};
if (options.EscapeInvalidIdentifiers)
decompiler.AstTransforms.Add(new EscapeInvalidIdentifiers());
SyntaxTree st = options.FullDecompilation
? decompiler.DecompileWholeModuleAsSingleFile()
: decompiler.DecompileModuleAndAssemblyAttributes();
WriteCode(output, options.DecompilerSettings, st, decompiler.TypeSystem);
return null;
}
/// <summary>
/// Runs <see cref="WholeProjectDecompiler"/> against the loaded assembly and emits a
/// buildable .csproj + per-type .cs files under
/// <see cref="DecompilationOptions.SaveAsProjectDirectory"/>. The <paramref name="output"/>
/// ITextOutput is the buffer the caller will display when the export finishes — we
/// write a short summary into it so the user gets feedback in the editor tab. The
/// project file's name is derived from the assembly's <see cref="MetadataFile.Name"/>
/// via <see cref="WholeProjectDecompiler.CleanUpFileName"/>.
/// </summary>
ProjectId? DecompileAsProject(LoadedAssembly assembly, MetadataFile module, ITextOutput output, DecompilationOptions options)
{
var targetDirectory = options.SaveAsProjectDirectory!;
var resolver = assembly.GetAssemblyResolver(loadOnDemand: options.DecompilerSettings.AutoLoadAssemblyReferences);
var debugInfo = assembly.GetDebugInfoOrNull();
var decompiler = new WholeProjectDecompiler(
options.DecompilerSettings,
resolver,
projectWriter: null,
assemblyReferenceClassifier: null,
debugInfoProvider: debugInfo);
var projectFileName = System.IO.Path.Combine(
targetDirectory,
WholeProjectDecompiler.CleanUpFileName(module.Name, ProjectFileExtension));
ProjectId? id;
using (var writer = new System.IO.StreamWriter(projectFileName))
id = decompiler.DecompileProject(module, targetDirectory, writer, options.CancellationToken);
output.WriteLine("// Project written to " + targetDirectory);
return id;
}
static List<EntityHandle> CollectFieldsAndCtors(ITypeDefinition type, bool isStatic)
{
var members = new List<EntityHandle>();
foreach (var field in type.Fields)
if (!field.MetadataToken.IsNil && field.IsStatic == isStatic)
members.Add(field.MetadataToken);
foreach (var e in type.Events)
if (!e.MetadataToken.IsNil && e.IsStatic == isStatic)
members.Add(e.MetadataToken);
foreach (var p in type.Properties)
if (!p.MetadataToken.IsNil && p.IsStatic == isStatic && !p.IsIndexer)
members.Add(p.MetadataToken);
foreach (var ctor in type.Methods)
if (!ctor.MetadataToken.IsNil && ctor.IsConstructor && ctor.IsStatic == isStatic)
members.Add(ctor.MetadataToken);
return members;
}
sealed class SelectCtorTransform(IMethod ctor) : IAstTransform
{
readonly HashSet<ISymbol?> removedSymbols = new();
public void Run(AstNode rootNode, TransformContext context)
{
ConstructorDeclaration? ctorDecl = null;
foreach (var node in rootNode.Children)
{
switch (node)
{
case ConstructorDeclaration cd:
if (cd.GetSymbol() == ctor)
ctorDecl = cd;
else
{
cd.Remove();
removedSymbols.Add(cd.GetSymbol());
}
break;
case FieldDeclaration fd:
if (fd.Variables.All(v => v.Initializer.IsNull))
{
fd.Remove();
removedSymbols.Add(fd.GetSymbol());
}
break;
case EventDeclaration ed:
if (ed.Variables.All(v => v.Initializer.IsNull))
{
ed.Remove();
removedSymbols.Add(ed.GetSymbol());
}
break;
case PropertyDeclaration pd:
if (pd.Initializer.IsNull)
{
pd.Remove();
removedSymbols.Add(pd.GetSymbol());
}
break;
case CustomEventDeclaration:
case IndexerDeclaration:
node.Remove();
removedSymbols.Add(node.GetSymbol());
break;
}
}
if (ctorDecl?.Initializer.ConstructorInitializerType == ConstructorInitializerType.This)
{
foreach (var node in rootNode.Children)
{
if (node is not ConstructorDeclaration)
{
node.Remove();
removedSymbols.Add(node.GetSymbol());
}
}
}
foreach (var node in rootNode.Children)
{
if (node is Comment && removedSymbols.Contains(node.GetSymbol()))
node.Remove();
}
}
}
sealed class SelectFieldTransform(IField field) : IAstTransform
{
public void Run(AstNode rootNode, TransformContext context)
{
foreach (var node in rootNode.Children)
{
switch (node)
{
case EntityDeclaration:
if (node.GetSymbol() != field)
node.Remove();
break;
case Comment c:
if (c.GetSymbol() != field)
node.Remove();
break;
}
}
}
}
static void WriteCode(ITextOutput output, DecompilerSettings settings, SyntaxTree syntaxTree, IDecompilerTypeSystem typeSystem)
{
syntaxTree.AcceptVisitor(new InsertParenthesesVisitor { InsertParenthesesForReadability = true });
output.IndentationString = settings.CSharpFormattingOptions.IndentationString;
TokenWriter tokenWriter = new TextTokenWriter(output, settings, typeSystem);
if (output is TextView.ISmartTextOutput smartOutput)
tokenWriter = new CSharpHighlightingTokenWriter(tokenWriter, smartOutput);
syntaxTree.AcceptVisitor(new CSharpOutputVisitor(tokenWriter, settings.CSharpFormattingOptions));
}
void AddWarningMessage(MetadataFile module, ITextOutput output, string line1, string? line2 = null,
string? buttonText = null, global::Avalonia.Media.IImage? buttonImage = null,
System.EventHandler<global::Avalonia.Interactivity.RoutedEventArgs>? buttonClickHandler = null)
{
if (output is TextView.ISmartTextOutput fancyOutput)
{
string text = line1;
if (!string.IsNullOrEmpty(line2))
text += System.Environment.NewLine + line2;
fancyOutput.AddUIElement(() => new global::Avalonia.Controls.StackPanel {
Margin = new global::Avalonia.Thickness(5),
Orientation = global::Avalonia.Layout.Orientation.Horizontal,
Children = {
new global::Avalonia.Controls.Image {
Width = 32,
Height = 32,
Source = Images.Images.Warning,
},
new global::Avalonia.Controls.TextBlock {
Margin = new global::Avalonia.Thickness(5, 0, 0, 0),
Text = text,
},
},
});
fancyOutput.WriteLine();
if (buttonText != null && buttonClickHandler != null)
{
fancyOutput.AddButton(buttonImage, buttonText, buttonClickHandler);
fancyOutput.WriteLine();
}
}
else
{
WriteCommentLine(output, line1);
if (!string.IsNullOrEmpty(line2))
WriteCommentLine(output, line2);
}
}
void AddReferenceAssemblyWarningMessage(MetadataFile module, ITextOutput output)
{
var metadata = module.Metadata;
if (!metadata.GetCustomAttributes(Handle.AssemblyDefinition).HasKnownAttribute(metadata, KnownAttribute.ReferenceAssembly))
return;
AddWarningMessage(module, output, Resources.WarningAsmMarkedRef);
}
void AddReferenceWarningMessage(MetadataFile module, ITextOutput output)
{
// Resolving AssemblyTreeModel via composition would create a circular registration
// (LanguageService → Language → AssemblyTreeModel → LanguageService). Match the WPF
// output by looking the assembly up directly off the module — same predicate (the
// metadata file equality), no service dependency.
if (!HasReferenceErrors(module))
return;
AddWarningMessage(module, output,
Resources.WarningSomeAssemblyReference,
Resources.PropertyManuallyMissingReferencesListLoadedAssemblies);
}
static bool HasReferenceErrors(MetadataFile module)
{
try
{
var atm = AppEnv.AppComposition.Current.GetExport<AssemblyTree.AssemblyTreeModel>();
var loadedAssembly = atm.AssemblyList?.GetAssemblies()
.FirstOrDefault(la => la.GetMetadataFileOrNull() == module);
return loadedAssembly?.LoadedAssemblyReferencesInfo.HasErrors == true;
}
catch
{
return false;
}
}
}
}