Accessing an instance variable by name (string), kinda like dynamic languages do, in C#

Question

i've got some C# code like this:

string fieldName = ...
string value = ...

if (fieldName == "a") a = value;
if (fieldName == "b") b = value;
if (fieldName == "c") c = value;
if (fieldName == "d") d = value;
...

I want something like this:

string fieldName = ...
string value = ...

SetMyInstanceVariable(fieldName, value);
...

Is there a simple way to do it? I know that given a class's name in a string, you can instantiate it with System.Activator, and this is kindof similar so i was hoping....

Answer 1

A Dictionary<string, string> is the easiest approach:

public class Bag {
  var props = new Dictionary<string, string>();

  // ...

  public string this[string key] {
    get { return props[key]; }
    set { props[key] = value; }
  }
}

The reflection approach is considerably more complex but still doable:

public class Fruit {
  private int calories = 0;
}

// ...

var f = new Fruit();
Type t = typeof(Fruit);

// Bind to a field named "calories" on the Fruit type.
FieldInfo fi = t.GetField("calories",
  BindingFlags.NonPublic | BindingFlags.Instance);

// Get the value of a field called "calories" on this object.
Console.WriteLine("Field value is: {0}", fi.GetValue(f));

// Set calories to 100. (Warning! Will cause runtime errors if types
// are incompatible -- try using "100" instead of the integer 100, for example.)
fi.SetValue(f, 100);

// Show modified value.
Console.WriteLine("Field value is: {0}", fi.GetValue(f));