Question

我正在尝试将表达式树导出到PE程序集作为主要入口点。我通过构建表达式树获得了Lambda Expression，例如：

using System.Linq;
using System;

// 1. use expression trees to create a block expression (not shown)

// 2. create a lambda expression: 
LambdaExpression exprLambda = Expression.Lambda(exprBlock, new ParameterExpression[0]);

MethodBuilder mbuilder = null;
// 3. ??? Somehow get a method builder instance that works ??? 

// 4. Compile the lambda using the MethodBuilder instance. 
exprLambda.CompileToMethod(mbuilder);

// 5. ??? Somehow get an AssemblyBuilder instance to .Save(..) this to disk.  ???

步骤3和5是我所缺少的。

Answer 1

不要只使用Expression.Compile，而是使用Expression.CompileToMethod(MethodBuilder)。

简短但完整的示例，它在磁盘上创建可执行文件，表达式树作为在入口点中执行的代码：

using System;
using System.Reflection;
using System.Reflection.Emit;
using System.Linq.Expressions;

class Program
{
    static void Main()
    {
        var asmName = new AssemblyName("Foo");
        var asmBuilder = AssemblyBuilder.DefineDynamicAssembly
            (asmName, AssemblyBuilderAccess.RunAndSave);
        var moduleBuilder = asmBuilder.DefineDynamicModule("Foo", "Foo.exe");

        var typeBuilder = moduleBuilder.DefineType("Program", TypeAttributes.Public);
        var methodBuilder = typeBuilder.DefineMethod("Main",
            MethodAttributes.Static, typeof(void), new[] { typeof(string) });

        Expression<Action> action = () => Console.WriteLine("Executed!");

        action.CompileToMethod(methodBuilder);

        typeBuilder.CreateType();
        asmBuilder.SetEntryPoint(methodBuilder);
        asmBuilder.Save("Foo.exe");
    }
}

如何将表达式树保存为新的可执行磁盘文件的主要入口点？

1 个答案: