C# Immutable Builders

gistfile1.cs

// Basically the important bit is near the bottom

public class MyFancyImmutableObject {
  public string FirstValue { get; private set; }
  public string SecondValue { get; private set; }
  public string ThirdValue { get; private set; }
  public string FourthValue { get; private set; }
  
  public MyFancyImmutableObject(string firstValue, string secondValue, string thirdValue,string fourthValue){
    FirstValue = firstValue;
    SecondValue = secondValue;
    ThirdValue = thirdValue;
    FourthValue = fourthValue;
  }
  
  public string SomethingAwesome(string wibble){
    return wibble; // but really you'd be doing something here
  }
  
  public int SomethingEquallyAmazing(string woo){
    return default(int);
  }
  
  public MyFancyImmutableObject KaPow(MyFancyImmutableObject anotherone){
    return this; // blah blah you get where this is going for the immutable object malarky
  }
}

public class MyFancyImmutableObjectBuilder {
  internal string FirstValue = "sensibledefault1";
  internal string SecondValue = "sensibledefault2";
  internal string ThirdValue = "sensibledefault3";
  internal string FourthValue = "sensibledefault4";
  
  public MyFancyImmutableObjectBuilder WhereTheFirstValueIs(string firstValue) {
    FirstValue = firstValue;
    return this;
  }
  public MyFancyImmutableObjectBuilder WhereTheSecondValueIs(string secondValue) {
    SecondValue = secondValue;
    return this;
  }
  public MyFancyImmutableObjectBuilder WhereTheThirdValueIs(string thirdValue) {
    ThirdValue = thirdValue;
    return this;
  }
  public MyFancyImmutableObjectBuilder WhereTheFourthValueIs(string fourthValue) {
    FourthValue = fourthValue;
    return this;
  }
  
  public static implicit operator MyFancyImmutableObject(MyFancyImmutableObjectBuilder value) {
    return new MyFancyImmutableObject(value.FirstValue, value.SecondValue, value.ThirdValue, value.FourthValue);
  }
}

public class ExampleForMyFancyImmutableObject{
  public void Go(){
    MyFancyImmutableObject b = (MyFancyImmutableObject)(new MyFancyImmutableObjectBuilder().
      WhereTheFirstValueIs("Hello").
      WhereTheSecondValueIs(" ").
      WhereTheFourthValueIs("!").
      WhereTheThirdValueIs("World"));
  }
}