Question

我面临以下代码，通过反思检索数据：

public object GetValue(object source)
{
    if (Member == null) return Argument;
    try
    {
        object[] argList = (Argument == null ? null : new object[] { Argument });
        if (Member is PropertyInfo) return ((PropertyInfo)Member).GetValue(source, argList);
        if (Member is MethodInfo) return ((MethodInfo)Member).Invoke(source, argList);
        if (Member is FieldInfo) return ((FieldInfo)Member).GetValue(source);
        throw new Exception("Unknown member type: " + Member);
    }
    catch (Exception ex)
    {
        throw new Exception("Could not get value " + Member.Name + " from " + source + " with " + Argument, ex);
    }
}

然而这很慢，我想用更快的东西取代反射，也许是代表？但是，我不确定代表是最佳选择还是在这种情况下如何实现它。我正在运行.NET 4.0。任何建议都表示赞赏！

Answer 1

这快一点

static Func<object, object[], object> BuildCaller(MethodInfo method)
{
    var obj = Expression.Parameter(typeof(object));
    var pars = Expression.Parameter(typeof(object[]));

    var pars2 = method.GetParameters();

    var casted = new Expression[pars2.Length];

    for (int i = 0; i < pars2.Length; i++)
    {
        casted[i] = Expression.Convert(Expression.ArrayAccess(pars, Expression.Constant(i)), pars2[i].ParameterType);
    }

    var call = Expression.Call(Expression.Convert(obj, method.DeclaringType), method, casted);
    var cast = Expression.Convert(call, typeof(object));
    var lamdba = Expression.Lambda<Func<object, object[], object>>(cast, obj, pars);
    return lamdba.Compile();
}

static Func<object, object[], object> BuildCaller(FieldInfo field)
{
    var obj = Expression.Parameter(typeof(object));
    var pars = Expression.Parameter(typeof(object[]));

    var call = Expression.Field(Expression.Convert(obj, field.DeclaringType), field);
    var cast = Expression.Convert(call, typeof(object));
    var lamdba = Expression.Lambda<Func<object, object[], object>>(cast, obj, pars);
    return lamdba.Compile();
}

static Func<object, object[], object> BuildCaller(PropertyInfo property)
{
    var obj = Expression.Parameter(typeof(object));
    var pars = Expression.Parameter(typeof(object[]));

    var pars2 = property.GetIndexParameters();

    var casted = new Expression[pars2.Length];

    for (int i = 0; i < pars2.Length; i++)
    {
        casted[i] = Expression.Convert(Expression.ArrayAccess(pars, Expression.Constant(i)), pars2[i].ParameterType);
    }

    var call = Expression.Property(Expression.Convert(obj, property.DeclaringType), property, casted);
    var cast = Expression.Convert(call, typeof(object));
    var lamdba = Expression.Lambda<Func<object, object[], object>>(cast, obj, pars);
    return lamdba.Compile();
}

我创建了一个委托（通过Expression）来预防该方法。如果Arguments被“修复”，您可以更进一步，甚至可以预先设置转换（就像每次调用方法时都进行转换一样）

这是方法的一个例子。对于属性和字段，它是相似的（对于字段来说，它更容易）。

使用示例

var fun = BuildCaller(typeof(MyClass).GetMethod("MyMethod"));
var mc = new MyClass();
fun(mc, new object[] { 1, 2.0 });

您必须将fun与Method

一起缓存

C＃.NET 4.0中Reflections的最佳替代品

1 个答案: