Variable as function call from external XML file

Question

I am writing a text file parser for a specific matching condition, and in a couple of the files I need to do some custom manipulation. What I would like to do is store the name of the custom procedure that is being used in an external XML file with the other rules. Most won't use this, and I found this answer regarding the action call:

Variable for function names

The above has the following dictionary definition

private static readonly IDictionary<string,Action<string>> actionByType =
    new Dictionary<string,Action<string>>

Element adding from XML file in my current program (These two elements will be added)

foreach (XmlNode node in nodes)
            {
                Client holding = new Client();

                holding.has_custom = 
                     Convert.ToBoolean(
                      node.SelectSingleNode("has_custom").InnerText);
                holding.custom_call = 
                     node.SelectSingleNode("custom_call").InnerText;

                clients.Add(holding);
            }

As I go through this, how do I assign the name of the custom call as an action to be called in the dictionary? And then do I use a case statement with the generic parse as the default?

I'm not sure what you're asking. In your example, actionByType is a dictionary. What are you proposing as an alternative? — JLRishe
– JLRishe, Commented May 22, 2014 at 18:59

CSharpie · Accepted Answer · 2014-05-22 19:21:52Z

1

Im not sure if I understand you correctly, but you can assign Actions / functions (Delegates to be more specific) like this:

actionByType.Add("write", text => Console.WriteLine(text));
actionByType.Add("write2", Console.WriteLine);

or like this:

void someAction(string someString)
{
     Console.WriteLine(someString);
}

...
actionByType.Add("write", someAction);

Then Invoke like this:

actionByType["write"]("Hello World!");

So in your case it would be:

actionByType[holding.custom_call]("What ever you need that string argument for");

Here is the fiddle https://dotnetfiddle.net/oFuEeF

answered May 22, 2014 at 19:21

CSharpie

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Comments

David · Accepted Answer · 2014-05-22 19:59:43Z

0

First, get the proper MethodInfo using reflection. This should be a static method, and should reside in a static class containing all your XML-accessible methods.

var method = typeof(MyStoredTypes).GetMethod(methodName, BindingFlags.Public | BindingFlags.Static)

You'll also need a ParameterExpression to capture the incoming string.

var param = Expression.Parameter(typeof(string));

Finally, System.Linq.Expression.Call to create the Expression tree for your call, Lambda it, and Compile it.

var act = Expression.Lambda<Action<string>>(
    Expression.Call(param, method),
    new ParameterExpression[] { param })
.Compile();

edited May 22, 2014 at 19:59

answered May 22, 2014 at 19:28

David

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