如何将可变数量的命名参数传递给方法？

Question

I understand how to get the names of parameters passed to a method, but let's say I have a method declaration as follows:

static void ParamsTest(string template, params object[] objects)

and I want to use object/property names in my template for substitution with real property values in any of the objects in my `objects' parameter. Let's then say I call this method with:

ParamsTest("Congrats", customer, purchase);

I will only be able to retrieve two parameter names trying to fill out the template, viz, template , and objects , and the names of the objects in the objects collection are forever lost, or not?

I could require a List<object> as my second parameter, but I feel there is somehow a more elegant solution, maybe with a lambda or something. I don't know, I'm not used to using lambdas outside of LINQ.

Answer 1

Inpsired by Mark I can offer an anonymous type answer :

using System;

namespace ConsoleApplication5
{
    class Program
    {
        static void Main(string[] args)
        {
            ParamsTest(new { A = "a", B = "b"});
        }

        public static void ParamsTest(object o)
        {
            if (o == null)
            {
                throw new ArgumentNullException();
            }
            var t = o.GetType();
            var aValue = t.GetProperty("A").GetValue(o, null);
            var bValue = t.GetProperty("B").GetValue(o, null);
        }
    }
}

However this DOES have drawbacks :

• No type safety. I can pass in any object
• I can pass in an anonymous type with different members and/or types than those expected
• You should also do more checking than in this short sample

Answer 2

You could define a parameters object :

public class ParamsTestParams {
    public string A { get; set; }
    public string B { get; set; }

    public static readonly ParamsTestParams Empty = new ParamsTestParams();
}

Change the methods signature to :

ParamsTest(ParamsTestParams parameters)

And call your method like so :

ParamsTest(new ParamsTestParams { A = "abc" });

or :

ParamsTest(new ParamsTestParams { B = "abc" });

or :

ParamsTest(new ParamsTestParams { A = "abc", B = "xyz" });

or :

ParamsTest(ParamsTestParams.Empty); // instead of null so you don't have to do null checks in the method's body

and so on.

Answer 3

I would probably just do it like this:

static void ParamsTest(string template, object[] objects)

and call it like this:

ParamsTest("Congrats", new object[] { customer, purchase });