How do I create a lambda expression of type Expression.Lambda<Action<Controller>>? dynamically

Question

I am trying to create a lambda expression of type Expression.Lambda<Action<Controller>> dynamically.

For instance: x => x.Index()

var body = ???
Expression<Action<Controller>> action = Expression.Lambda<Action<Controller>>(body);

I have the controller type (Type) and the controller action (MemberInfo).

You mean the actual controller is a type derived from Controller? So you actually want something like x => ((ConcreteController)x).Index()? — svick
– svick, Commented Oct 14, 2012 at 15:15
The Controller class is belonging to ASP.NET MVC. All controllers are derived from this class. I also could change my question into: How do I create a lambda expression of type Expression.Lambda<Action<T>>? — Rookian
– Rookian, Commented Oct 14, 2012 at 15:17

svick · Accepted Answer · 2012-10-14 15:26:16Z

2

If I understand your question correctly, you would do it using Expression.Call(). Something like:

Expression<Action<T>> CreateCallExpression<T>(MethodInfo method)
{
    var parameter = Expression.Parameter(typeof(T), "x");
    return Expression.Lambda<Action<T>>(
        Expression.Call(parameter, method), parameter);
}

answered Oct 14, 2012 at 15:26

svick

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4 Comments

Rookian Over a year ago

Do you know how can I add method parameters? I tried Expression.Paramter and Expression.Variable with no success.

svick Over a year ago

That depends, where do you get the value for that parameter? Should it be constant, or from parameter of the expression, or something else?

Rookian Over a year ago

It should be constant default values (default(T) if possible.

svick Over a year ago

In that case, something like Expression.Call(parameter, method, Expression.Default(typeof(ParameterType))) should work for a method with one parameter.

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