Question

I want to build a method which accepts a string param, and an object which I would like to return a particular member of based on the param. So, the easiest method is to build a switch statement:

public GetMemberByName(MyObject myobj, string name)
{
   switch(name){
     case "PropOne": return myobj.prop1;
     case "PropTwo": return myobj.prop2; 
   }
}

This works fine, but I may wind up with a rather large list… So I was curious if there’s a way, without writing a bunch of nested if-else structures, to accomplish this in an indexed way, so that the matching field is found by index instead of falling through a switch until a match is found.

I considered using a Dictionary<string, something> to give fast access to the matching strings (as the key member) but since I’m wanting to access a member of a passed-in object, I’m not sure how this could be accomplished.

• I’m specifically trying to avoid reflection etc in order to have a very fast implementation. I’ll likely use code generation, so the solution doesn’t need to be small/tight etc.

• I originally was building a dictionary of but each object was initializing it. So I began to move this to a single method that can look up the values based on the keys- a switch statement. But since I’m no longer indexed, I’m afraid the continuous lookups calling this method would be slow.

• SO: I am looking for a way to combine the performance of an indexed/hashed lookup (like the Dictionary uses) with returning particular properties of a passed-in object. I’ll likely put this in a static method within each class it is used for.

Answer 1

Here’s an easy way you can use a dictionary:

    Dictionary<string, Func<MyObject, object>> propertyNameAssociations;

    private void BuildPropertyNameAssociations()
    {
        propertyNameAssociations = new Dictionary<string, Func<MyObject, object>>();
        propertyNameAssociations.Add("PropOne", x => x.prop1);
        propertyNameAssociations.Add("PropTwo", x => x.prop2);
    }

    public object GetMemberByName(MyObject myobj, string name)
    {
        if (propertyNameAssociations.Contains(name))
            return propertyNameAssociations[name](myobj);
        else
            return null;
    }