Question

This is an interesting concept which i couldn’t figure out how to implement. (its related to a university assignment where i need to deploy the decorator pattern).

I’ve written rough C# code below which won’t compile however, Suppose, i have a class

Class A {
   public int A { get; set; }
   public string B { get; set; }
   public float C { get; set; }

   public string concatFields() {
       string sample = null;
       foreach (Field f in this) {
           sample += f.ToString();
       }
       return sample;
   }
}

How in terms would you achieve the concatFields method? Is there a way to iterate through the class’s fields (without knowing the names of the fields) and call ToString() on each.

In example B scenario, how would you apply the same method on all Fields provided they were the same type.

Cheers guys for the help, i’ve tagged this with C# but not sure what other tags could be applied

Answer 1

You can use reflection, iterate over metadata of your class, and pull fields through the reflection API. Obviously, there is a cost attached to that: using reflection is slower than accessing fields directly; sometimes, considerably. However, you can certainly do it. Here is an example:

MyClass obj = new MyClass();
// Set fields in the obj...
var fields = typeof(MyClass).GetFields(System.Reflection.BindingFlags.GetField);
StringBuilder res = new StringBuilder();
foreach (FieldInfo f in fields) {
    var val = f.GetValue(obj);
    if (val != null) res.Append(val.ToString());
}
Console.WriteLine(res.ToString());

FieldInfo class exposes many useful properties, such as Name and Type, letting you pick which fields to include in your processing, and which fields to ignore.