我怎样才能使这项工作有深刻的性能 [英] How can I make this work with deep properties

问题描述

由于以下code ...

Given the following code...

class Program {

    static void Main(string[] args) {

        Foo foo = new Foo { Bar = new Bar { Description= "Martin" }, Name = "Martin" };

        DoLambdaStuff(foo, f => f.Name);
        DoLambdaStuff(foo, f => f.Bar.Description);

    }

    static void DoLambdaStuff<TObject, TValue>(TObject obj, Expression<Func<TObject, TValue>> expression) {

        // Set up and test "getter"...

        Func<TObject, TValue> getValue = expression.Compile();

        TValue stuff = getValue(obj);

        // Set up and test "setter"...

        ParameterExpression objectParameterExpression = Expression.Parameter(typeof(TObject)), valueParameterExpression = Expression.Parameter(typeof(TValue));
        Expression<Action<TObject, TValue>> setValueExpression = Expression.Lambda<Action<TObject, TValue>>(
            Expression.Block(
                Expression.Assign(Expression.Property(objectParameterExpression, ((MemberExpression)expression.Body).Member.Name), valueParameterExpression)
            ), objectParameterExpression, valueParameterExpression
        );
        Action<TObject, TValue> setValue = setValueExpression.Compile();


        setValue(obj, stuff);

    }

}

class Foo {

    public Bar Bar { get; set; }
    public string Name { get; set; }

}

class Bar {

    public string Description{ get; set; }

}

到呼叫DoLambdaStuff（FOO，F =＆GT; f.Name）工作正常，因为我访问一个浅浅的财产，但在调用 DoLambdaStuff（FOO，F =＆GT; f.Bar.Description）失败 - 尽管在创建的getValue 功能正常工作，创造在 setValueEx pression 失败，因为我试图访问该对象的深层属性。

The call to DoLambdaStuff(foo, f => f.Name) works ok because I am accessing a shallow property, however the call to DoLambdaStuff(foo, f => f.Bar.Description) fails - although the creation of the getValue function works fine, the creation of the setValueExpression fails because I am attempting to access a deep property of the object.

任何人都可以请帮我修改，这样我可以创建 setValueEx pression 深性能以及浅？

Can anybody please help me to modify this so that I can create the setValueExpression for deep properties as well as shallow?

感谢。

推荐答案

您需要考虑的事实，你的前pression.Body已经重新presenting要设置的属性优势。这意味着您可以使用EX pression.Body为左手侧的分配前pression：

You need to take advantage of the fact that your expression.Body is already representing the property you want to set. This means you can use expression.Body as the left-hand-side in your assignment expression:

    public static void Main(string[] args)
    {
        Foo foo = new Foo { Bar = new Bar { Name = "Martin", Buzz = new Fiz() { Name = "Carl" }}, Name = "Martin" };

        DoLambdaStuff(foo, f => f.Bar.Name, "Dennis");
        DoLambdaStuff(foo, f => f.Bar.Buzz.Name, "Dennis");
        Console.WriteLine(foo.Bar.Name);
        Console.WriteLine(foo.Bar.Buzz.Name);

    }
    static void DoLambdaStuff<TObject, TValue>(TObject obj, Expression<Func<TObject, TValue>> expression, TValue valueToSet)
    {
        // Getter.
        Func<TObject, TValue> getter = expression.Compile();
        TValue stuff = getter(obj);

        ParameterExpression pObj = expression.Parameters[0];
        ParameterExpression pValue = Expression.Parameter(typeof (TValue), "value");
        var setterBlock = Expression.Block(
            Expression.Assign(expression.Body, pValue)
            );

        var setterExpression = Expression.Lambda<Action<TObject, TValue>>(setterBlock, pObj, pValue);
        Action<TObject, TValue> setter = setterExpression.Compile();

        // Test 
        setter(obj,valueToSet);
    }

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