CIL（MSIL）中的StringBuilder

Question

CIL（MSIL）中的StringBuilder

5

我正在尝试生成代码，它接收一个 StringBuilder 并将类中所有属性的值写入字符串。我编写了以下代码，但目前遇到“Invalid method token”错误：

    public static DynamicAccessor<T> CreateWriter(T target) //Target class to *serialize*
    {
        DynamicAccessor<T> dynAccessor = new DynamicAccessor<T>();

        MethodInfo AppendMethod = typeof(StringBuilder).GetMethod("Append", new[] { typeof(Object) }); //Append method of Stringbuilder

        var method = new DynamicMethod("ClassWriter", typeof(StringBuilder), new[] { typeof(T) }, typeof(T), true);
        var generator = method.GetILGenerator();
        LocalBuilder sb = generator.DeclareLocal(typeof(StringBuilder)); //sb pointer


        generator.Emit(OpCodes.Newobj, typeof(StringBuilder)); //make our string builder 
        generator.Emit(OpCodes.Stloc, sb);                     //make a pointer to our new sb


        //iterate through all the instance of T's props and sb.Append their values.
        PropertyInfo[] props = typeof(T).GetProperties();
        foreach (var info in props)
        {
            generator.Emit(OpCodes.Callvirt, info.GetGetMethod()); //call the Getter
            generator.Emit(OpCodes.Ldloc, sb);                     //load the sb pointer
            generator.Emit(OpCodes.Callvirt, AppendMethod);        //Call Append 
        }

        generator.Emit(OpCodes.Ldloc, sb);
        generator.Emit(OpCodes.Ret);           //return pointer to sb

        dynAccessor.WriteHandler = method.CreateDelegate(typeof(Write)) as Write;
        return dynAccessor;
    }

有什么想法吗？提前感谢 :)

- Josh

1个回答

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- Marc Gravell · Accepted Answer

任何值类型的属性（如int）都需要装箱；或者您需要使用不同的Append重载。

另外：

每次需要加载对象（arg0）
StringBuilder.Append是一种流畅的API；您需要弹出该值，或者重新使用它：
因此，您不需要该字段

（个人而言，我会返回一个string，但是“嘿”）

就像这样：

    DynamicAccessor<T> dynAccessor = new DynamicAccessor<T>();
    MethodInfo AppendMethod = typeof(StringBuilder).GetMethod("Append", new[] { typeof(Object) }); //Append method of Stringbuilder

    var method = new DynamicMethod("ClassWriter", typeof(StringBuilder), new[] { typeof(T) }, typeof(T), true);
    var generator = method.GetILGenerator();
    generator.Emit(OpCodes.Newobj, typeof(StringBuilder).GetConstructor(Type.EmptyTypes)); //make our string builder 
    //iterate through all the instance of T's props and sb.Append their values.
    PropertyInfo[] props = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance);
    foreach (var info in props)
    {   
        generator.Emit(OpCodes.Ldarg_0);
        generator.Emit(OpCodes.Callvirt, info.GetGetMethod()); //call the Getter
        if (info.PropertyType.IsValueType)
        {
            generator.Emit(OpCodes.Box, info.PropertyType);
        }
        generator.Emit(OpCodes.Callvirt, AppendMethod);        //Call Append 
    }
    generator.Emit(OpCodes.Ret);           //return pointer to sb

这将生成相当于以下内容的代码：

StringBuilder ClassWriter(T obj) {
    return new StringBuilder.Append((object)obj.Foo).Append((object)obj.Bar)
                   .Append((object)obj.Blip).Append((object)obj.Blap);
}