從PropertyInfo獲取訪問器作為Func <object>和Action <object>委托

Question

我需要調用在運行時通過反射確定的屬性，並以高頻率調用它們。 所以我正在尋找具有最佳性能的解決方案，這意味着我可能會避免反思。 我在考慮將屬性訪問器存儲為列表中的Func和Action委托，然后調用它們。

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);
    }
}

現在的問題是，如何將訪問器分離為Func和Action為以后的調用進行分類？

仍然使用反射進行調用的天真實現如下所示：

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);
}

如何在沒有refelections的情況下實現上述方法。 表達式是最快的方式嗎？ 我試過使用這樣的表達式：

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();
}

但是在這里GetSetter的最后一行如果屬性的類型不完全是System.Object類型，我得到以下的GetSetter ：

ArgumentException：類型為'System.Boolean'的ParameterExpression不能用於'System.Object'類型的委托參數

Answer 1

這是我的方式，它工作正常。

但我不知道它的表現。

    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

我認為你需要做的是將Lamda作為正確的類型返回，以object作為參數，但是在調用setter之前，在表達式中將轉換為正確的類型：

 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();

  }

實例： http ： //rextester.com/HWVX33724

Answer 3

您需要使用Convert.ChangeType類的轉換方法。 物業的類型是布爾。 但GetSetter方法的返回類型是對象。 所以你應該將表達式中bool的屬性類型轉換為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();
    }

現場演示

編輯：

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
}

您可以從字典中獲取值，如下所示：

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

現場演示