Question

我需要调用在运行时通过反射确定的属性，并以高频率调用它们。所以我正在寻找具有最佳性能的解决方案，这意味着我可能会避免反思。我在考虑将属性访问器存储为列表中的Func和Action委托，然后调用它们。

private readonly Dictionary<string, Tuple<Func<object>, Action<object>>> dataProperties =
        new Dictionary<string, Tuple<Func<object>, Action<object>>>();

private void BuildDataProperties()
{
    foreach (var keyValuePair in this.GetType()
        .GetProperties(BindingFlags.Instance | BindingFlags.Public)
        .Where(p => p.Name.StartsWith("Data"))
        .Select(
            p =>
                new KeyValuePair<string, Tuple<Func<object>, Action<object>>>(
                    p.Name,
                    Tuple.Create(this.GetGetter(p), this.GetSetter(p)))))
    {
        this.dataProperties.Add(keyValuePair.Key, keyValuePair.Value);
    }
}

现在的问题是，我如何将访问器分解为Func和Action为后来的调用进行分类？

仍然使用反射进行调用的天真实现如下所示：

private Func<object> GetGetter(PropertyInfo info)
{
    // 'this' is the owner of the property
    return () => info.GetValue(this);
}

private Action<object> GetSetter(PropertyInfo info)
{
    // 'this' is the owner of the property
    return v => info.SetValue(this, v);
}

如何在没有refelections的情况下实现上述方法。表达式是最快的方式吗？我尝试过使用这样的表达式：

private Func<object> GetGetter(PropertyInfo info)
{
    // 'this' is the owner of the property
    return
        Expression.Lambda<Func<object>>(
            Expression.Convert(Expression.Call(Expression.Constant(this), info.GetGetMethod()), typeof(object)))
            .Compile();
}

private Action<object> GetSetter(PropertyInfo info)
{
    // 'this' is the owner of the property
    var method = info.GetSetMethod();
    var parameterType = method.GetParameters().First().ParameterType;
    var parameter = Expression.Parameter(parameterType, "value");
    var methodCall = Expression.Call(Expression.Constant(this), method, parameter);

    // ArgumentException: ParameterExpression of type 'System.Boolean' cannot be used for delegate parameter of type 'System.Object'
    return Expression.Lambda<Action<object>>(methodCall, parameter).Compile();
}

但是这里GetSetter的最后一行如果属性的类型不完全是System.Object类型，我会得到以下激励：

ArgumentException：类型为“System.Boolean”的ParameterExpression不能用于'System.Object'
类型的委托参数

Answer 1

这是我的方式，它运作正常。

但我不知道它的表现。

    public static Func<object, object> GenerateGetterFunc(this PropertyInfo pi)
    {
        //p=> ((pi.DeclaringType)p).<pi>

        var expParamPo = Expression.Parameter(typeof(object), "p");
        var expParamPc = Expression.Convert(expParamPo,pi.DeclaringType);

        var expMma = Expression.MakeMemberAccess(
                expParamPc
                , pi
            );

        var expMmac = Expression.Convert(expMma, typeof(object));

        var exp = Expression.Lambda<Func<object, object>>(expMmac, expParamPo);

        return exp.Compile();
    }

    public static Action<object, object> GenerateSetterAction(this PropertyInfo pi)
    {
        //p=> ((pi.DeclaringType)p).<pi>=(pi.PropertyType)v

        var expParamPo = Expression.Parameter(typeof(object), "p");
        var expParamPc = Expression.Convert(expParamPo,pi.DeclaringType);

        var expParamV = Expression.Parameter(typeof(object), "v");
        var expParamVc = Expression.Convert(expParamV, pi.PropertyType);

        var expMma = Expression.Call(
                expParamPc
                , pi.GetSetMethod()
                , expParamVc
            );

        var exp = Expression.Lambda<Action<object, object>>(expMma, expParamPo, expParamV);

        return exp.Compile();
    }

Answer 2

我认为您需要做的是将Lamda作为正确的类型返回，并以object作为参数，但在调用setter之前，在表达式中将转换为正确的类型：

 private Action<object> GetSetter(PropertyInfo info)
 {
     // 'this' is the owner of the property
     var method = info.GetSetMethod();
     var parameterType = method.GetParameters().First().ParameterType;

     // have the parameter itself be of type "object"
     var parameter = Expression.Parameter(typeof(object), "value");

     // but convert to the correct type before calling the setter
     var methodCall = Expression.Call(Expression.Constant(this), method, 
                        Expression.Convert(parameter,parameterType));

     return Expression.Lambda<Action<object>>(methodCall, parameter).Compile();

  }

实例：http://rextester.com/HWVX33724

Answer 3

您需要使用Convert.ChangeType之类的转换方法。物业的类型是布尔。但GetSetter方法的返回类型是对象。因此，您应该将表达式中bool的属性类型转换为object。

    public static Action<T, object> GetSetter<T>(T obj, string propertyName)
    {
        ParameterExpression targetExpr = Expression.Parameter(obj.GetType(), "Target");
        MemberExpression propExpr = Expression.Property(targetExpr, propertyName);
        ParameterExpression valueExpr = Expression.Parameter(typeof(object), "value");
        MethodCallExpression convertExpr = Expression.Call(typeof(Convert), "ChangeType", null, valueExpr, Expression.Constant(propExpr.Type));
        UnaryExpression valueCast = Expression.Convert(convertExpr, propExpr.Type);
        BinaryExpression assignExpr = Expression.Assign(propExpr, valueCast);
        return Expression.Lambda<Action<T, object>>(assignExpr, targetExpr, valueExpr).Compile();
    }

    private static Func<T, object> GetGetter<T>(T obj, string propertyName)
    {
        ParameterExpression arg = Expression.Parameter(obj.GetType(), "x");
        MemberExpression expression = Expression.Property(arg, propertyName);
        UnaryExpression conversion = Expression.Convert(expression, typeof(object));
        return Expression.Lambda<Func<T, object>>(conversion, arg).Compile();
    }

LIVE DEMO

修改

public class Foo { #region Fields private readonly Dictionary<string, Tuple<Func<Foo, object>, Action<Foo, object>>> dataProperties = new Dictionary<string, Tuple<Func<Foo, object>, Action<Foo, object>>>(); #endregion #region Properties public string Name { get; set; } public string Data1 { get; set; } public string Data2 { get; set; } public string Data3 { get; set; } public int ID { get; set; } #endregion #region Methods: public public void BuildDataProperties() { foreach ( var keyValuePair in GetType() .GetProperties(BindingFlags.Instance | BindingFlags.Public) .Where(p => p.Name.StartsWith("Data")) .Select(p => new KeyValuePair<string, Tuple<Func<Foo, object>, Action<Foo, object>>>(p.Name, Tuple.Create(GetGetter(this, p.Name), GetSetter(this, p.Name))))) { dataProperties.Add(keyValuePair.Key, keyValuePair.Value); } } #endregion #region Methods: private private Func<T, object> GetGetter<T>(T obj, string propertyName) { ParameterExpression arg = Expression.Parameter(obj.GetType(), "x"); MemberExpression expression = Expression.Property(arg, propertyName); UnaryExpression conversion = Expression.Convert(expression, typeof(object)); return Expression.Lambda<Func<T, object>>(conversion, arg).Compile(); } private Action<T, object> GetSetter<T>(T obj, string propertyName) { ParameterExpression targetExpr = Expression.Parameter(obj.GetType(), "Target"); MemberExpression propExpr = Expression.Property(targetExpr, propertyName); ParameterExpression valueExpr = Expression.Parameter(typeof(object), "value"); MethodCallExpression convertExpr = Expression.Call(typeof(Convert), "ChangeType", null, valueExpr, Expression.Constant(propExpr.Type)); UnaryExpression valueCast = Expression.Convert(convertExpr, propExpr.Type); BinaryExpression assignExpr = Expression.Assign(propExpr, valueCast); return Expression.Lambda<Action<T, object>>(assignExpr, targetExpr, valueExpr).Compile(); } #endregion }

您可以从下面的字典中获取值：

var t = new Foo { ID = 1, Name = "Bla", Data1 = "dadsa"}; t.BuildDataProperties(); var value = t.dataProperties.First().Value.Item1(t);

LIVE DEMO

从PropertyInfo获取访问器作为Func <object>和Action <object>委托</object> </object>

3 个答案: