声明 Func<in T，out Result>动态地 [英] Declaring Func&lt;in T, out Result&gt; dynamically

问题描述

考虑一下:

var propertyinfo = typeof(Customer).GetProperty(sortExpressionStr);
Type orderType = propertyinfo.PropertyType;

现在我要声明

Func<int,orderType>

我知道这是不可能的，因为 ordertype 是在运行时，但有什么解决方法吗?

I know its not possible directly since ordertype is at runtime but is there is any workaround ?

这正是我想要做的:

var propertyinfo = typeof(T).GetProperty(sortExpressionStr);
Type orderType = propertyinfo.PropertyType;

var param = Expression.Parameter(typeof(T), "x");
var sortExpression = (Expression.Lambda<Func<T, orderType>>
   (Expression.Convert(Expression.Property(param, sortExpressionStr), typeof(orderType)), param));

这一切都是因为我想转换:

all this because I want to convert:

Expression<Func<T,object>> to Expression<Func<T,orderType>>

或者如果不可能，那么我想从一开始就用正确的类型创建它，情况如下:

or if its not possible then I want to create it from the first place with the right type , the case is as following:

我在一个具有 type(Customer) 和该类型的属性名称的方法中，我想通过它进行排序，我想创建一个排序表达式树以将其传递给 <代码>Orderby(这里).

I'm inside a method which have a type(Customer) and a property name of that type I want to order by it , I want to create a sort expression tree to pass it to Orderby (here).

推荐答案

linqClass.OrderBy(GetSortExpression(sortstr));


public static Expression<Func<T,object>> GetSortExpression<T>(string sortExpressionStr)
    {
        var param = Expression.Parameter(typeof(T), "x");
        var sortExpression = Expression.Lambda<Func<T, object>>(Expression.Property(param, sortExpressionStr), param);
        return sortExpression;
    }

这有效，我的问题是我过去常常传递额外的参数 Typeof(Object) 和 orderby 用来告诉我它不能按对象类型排序.谢谢大家

this worked my problem was i used to pass extra parameter Typeof(Object) and orderby used to tell me it cant sort by Object type. thanks all

感谢 dtb，我会检查您的答案是否也有效，如果有效，我将接受它，如果无效，我将接受该答案.

thanks dtb i will check if your answer work too and i will accept it if it works if not i will accept thsi one.

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