.NET 9 Emit API生成程序集报错：找不到System.Private.CoreLib

问题场景 #

使用.NET 9新的Emit API编程生成可执行程序集，测试代码如下：

PersistedAssemblyBuilder assemblyBuilder = new(new AssemblyName("HelloWorldTest"), typeof(object).Assembly);
TypeBuilder typeBuilder = assemblyBuilder.DefineDynamicModule("HelloWorldTest").DefineType("HelloWorldTest", TypeAttributes.Public | TypeAttributes.Class);

MethodBuilder methodBuilder = typeBuilder.DefineMethod("Main", MethodAttributes.Public | MethodAttributes.Static, typeof(void), [typeof(string[])]);

ILGenerator ilGenerator = methodBuilder.GetILGenerator();

Assembly loadedAssembly = AssemblyLoadContext.Default.LoadFromAssemblyPath(typeof(Console).Assembly.Location);

ilGenerator.Emit(OpCodes.Ldstr, "Hello, World!");
ilGenerator.Emit(OpCodes.Call, loadedAssembly.GetType("System.Console").GetMethod("WriteLine", [typeof(string)]));
ilGenerator.Emit(OpCodes.Ret);

typeBuilder.CreateType();

MetadataBuilder metadataBuilder = assemblyBuilder.GenerateMetadata(out BlobBuilder ilStream, out BlobBuilder fieldData);
PEHeaderBuilder peHeaderBuilder = new(imageCharacteristics: Characteristics.ExecutableImage);

ManagedPEBuilder peBuilder = new(
                header: peHeaderBuilder,
                metadataRootBuilder: new MetadataRootBuilder(metadataBuilder),
                ilStream: ilStream,
                mappedFieldData: fieldData,
                entryPoint: MetadataTokens.MethodDefinitionHandle(methodBuilder.MetadataToken));

BlobBuilder peBlob = new();
peBuilder.Serialize(peBlob);
using FileStream fileStream = new("HelloWorldTest.exe", FileMode.Create, FileAccess.Write);
peBlob.WriteContentTo(fileStream);

运行生成的HelloWorldTest.exe时触发错误：

Unhandled Exception: System.IO.FileNotFoundException: The file or assembly “System.Private.CoreLib, Version=9.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e” or one of its dependencies was not found. The system cannot find the specified file.

解决方法 #

1. 显式添加核心库引用 #

生成的程序集需要明确引用System.Private.CoreLib（.NET 9的核心基础库），修改程序集初始化代码：

Assembly coreLibAssembly = typeof(object).Assembly;
AssemblyName assemblyName = new AssemblyName("HelloWorldTest")
{
    Version = new Version(1, 0, 0, 0)
};
PersistedAssemblyBuilder assemblyBuilder = new(assemblyName, coreLibAssembly);

2. 简化Console方法调用 #

无需手动加载程序集，直接通过反射获取Console.WriteLine方法，避免路径加载问题：

MethodInfo writeLineMethod = typeof(Console).GetMethod("WriteLine", new[] { typeof(string) })!;
ilGenerator.Emit(OpCodes.Ldstr, "Hello, World!");
ilGenerator.Emit(OpCodes.Call, writeLineMethod);
ilGenerator.Emit(OpCodes.Ret);

3. 完善PE构建配置 #

添加目标框架属性，确保运行时能识别依赖环境：

// 添加目标框架标识
CustomAttributeBuilder targetFrameworkAttr = new(
    typeof(TargetFrameworkAttribute).GetConstructor(new[] { typeof(string) })!,
    new object[] { ".NETCoreApp,Version=v9.0" });
assemblyBuilder.SetCustomAttribute(targetFrameworkAttr);

// 构建PE时包含核心库引用
ManagedPEBuilder peBuilder = new(
    header: peHeaderBuilder,
    metadataRootBuilder: new MetadataRootBuilder(metadataBuilder),
    ilStream: ilStream,
    mappedFieldData: fieldData,
    entryPoint: MetadataTokens.MethodDefinitionHandle(methodBuilder.MetadataToken),
    assemblyReferences: new[] { coreLibAssembly.GetName() }
);

4. 确保运行环境正确 #

生成的可执行文件需要在安装了**.NET 9 Runtime**的环境中运行，无需手动复制核心库文件到程序目录。

内容的提问来源于stack exchange，提问作者Noraa Junker-Wildi