I have a problem with operator resolution on generic methods.
From my understanding of section 7.3.4 of the spec within the function EqualOperatorGeneric (sample code below) the correct overload of the == operator on the type A should be found, but instead it seems to get the candidate for (object, object).
Am I doing something very obvious wrong? Is there a method to get the expected behaviour and if not can I turn the given case into a compile time or runtime error?
public class A
{
public A(int num)
{
this.Value = num;
}
public int Value { get; private set; }
public override bool Equals(object obj)
{
var other = obj as A;
if (Object.ReferenceEquals(other, null))
return false;
return Object.Equals(this.Value, other.Value);
}
public override int GetHashCode()
{
return this.Value.GetHashCode();
}
public static bool operator ==(A l, A r)
{
if (Object.ReferenceEquals(l, null))
{
return !Object.ReferenceEquals(r, null);
}
return l.Equals(r);
}
public static bool operator !=(A l, A r)
{
return !(l == r);
}
}
class Program
{
static void Main(string[] args)
{
Console.WriteLine(EqualOperatorGeneric(new A(1), new A(1)));
}
public static bool EqualOperatorGeneric<L, R>(L l, R r)
where L : class
where R : class
{
return l == r;
}
}
Output:
False
When EqualOperatorGeneric is compiled the == operator needs to be bound statically, when the method is compiled, to a single implementation. It is not bound separately for each separate usage of the generic method.
This is what differentiates generics from, say, C++ templates. The generic method is compiled once and then applied to every usage with every set of type arguments, whereas templates are compiled separately for each set of generic arguments.
After scrounging the spec I realized you can use the dynamic keyword to defer binding of the operator from compile time to runtime. This fixes the issues I have been having:
public static bool EqualOperatorGeneric<L, R>(L l, R r)
{
dynamic dl = l, dr = r;
return dl == dr;
}
Related
I have a struct representing a Measure in my program, which I want to be interchangeable with double.
I have implemented it, and everything seems to be working fine, except for one of my tests:
[Test]
public void TestMeasureDefaultConstructor()
{
Measure m = new Measure();
// These pass
Assert.That(m.Equals(0), Is.True);
Assert.That(0 == m, Is.True);
Assert.That((double) m, Is.EqualTo(0));
Assert.That((float) m, Is.EqualTo(0));
Assert.That(0, Is.EqualTo(m));
// The next two fail
Assert.That(m, Is.EqualTo(0.0));
Assert.That(0.0.Equals(m), Is.True);
}
Everything works up to the line with Is.EqualTo(0.0).
The two lines testing that 0.0 Equals m each fail as follows:
Message: Expected: 0.0d
But was: MyCode.Model.Measure
(obviously only the first fails, so I have to swap them round to prove this).
I have clearly implemented Equals for my Measure class sufficiently, but I can't work out how to extend double.Equals to make the last two work. I have done a lot of searches, but keep coming on how to implement Equals for my class rather than the other way round.
Here is my class, possibly overkill now after trying all sorts of ways to make it work:
/// <summary>
/// The Measure class encapsulates the unit of measurement.
/// </summary>
public struct Measure
{
#region Construction and destruction
public Measure(double v)
{
Value = v;
}
#endregion
#region Conversions
public static implicit operator Measure(double v)
{
return new Measure(v);
}
public static implicit operator double(Measure m)
{
return m.Value;
}
public static implicit operator float(Measure m)
{
return (float) m.Value;
}
#endregion
#region Properties
public double Value { get; set; }
#endregion
#region Equality
public static bool Equals(Measure a, Measure b)
{
// Constants.IsEqual checks abs(a - b) < Tolerance.
return Constants.IsEqual(a.Value, b.Value);
}
public static bool Equals(Measure a, object b)
{
return a.Equals(b);
}
public static bool Equals(object a, Measure b)
{
return b.Equals(a);
}
public bool Equals(Measure other)
{
return Equals(this, other);
}
public override bool Equals(object obj)
{
if (ReferenceEquals(null, obj))
return false;
try
{
double d = Convert.ToDouble(obj);
return Equals(d);
}
catch (InvalidCastException)
{
return false;
}
catch (Exception e)
{
// Shouldn't get here!
Debug.Print("Unexpected exception in Measure.Equals: ", e);
if (System.Diagnostics.Debugger.IsAttached)
System.Diagnostics.Debugger.Break();
return false;
}
}
public static bool operator == (Measure x, Measure y)
{
return x.Equals(y);
}
public static bool operator != (Measure x, Measure y)
{
return !(x == y);
}
public override int GetHashCode()
{
return Value.GetHashCode();
}
#endregion
}
I have created a couple of extension methods:
public static class ExtensionMethods
{
public static bool Equals(this object a, Measure b)
{
return b.Equals(a);
}
public static bool Equals(this double a, Measure b)
{
return b.Equals(a);
}
}
I have put breakpoints on every Equals function, and they get hit during the passing tests, but none of these functions gets called for double.Equals so clearly the compiler doesn't think any of them are compatible.
Is this possible? If so, what am I missing, and how do I implement it?
Thanks in advance for any pointers.
Ian
Why does this program print "not added" while I think it should print "added"?
using System;
using System.Collections.Generic;
class Element
{
public int id;
public Element(int id)
{
this.id = id;
}
public static implicit operator Element(int d)
{
Element ret = new Element(d);
return ret;
}
public static bool operator ==(Element e1, Element e2)
{
return (e1.id == e2.id);
}
public static bool operator !=(Element e1, Element e2)
{
return !(e1.id == e2.id);
}
}
class MainClass
{
public static void Main(string[] args)
{
List<Element> element = new List<Element>();
element.Add(2);
if(element.Contains(2))
Console.WriteLine("added");
else
Console.WriteLine("not added");
}
}
The Contains method does not use the == operator. What is the problem?
The Contains method does not use the == operator
No - it uses Equals, which you haven't overridden... so you're getting the default behaviour of Equals, which is to check for reference identity instead. You should override Equals(object) and GetHashCode to be consistent with each other - and for sanity's sake, consistent with your == overload too.
I'd also recommend implementing IEquatable<Element>, which List<Element> will use in preference to Equals(object), as EqualityComparer<T>.Default picks it up appropriately.
Oh, and your operator overloads should handle null references, too.
I'd also strongly recommend using private fields instead of public ones, and making your type immutable - seal it and make id readonly. Implementing equality for mutable types can lead to odd situations. For example:
Dictionary<Element, string> dictionary = new Dictionary<Element, string>();
Element x = new Element(10);
dictionary[x] = "foo";
x.id = 100;
Console.WriteLine(dictionary[x]); // No such element!
This would happen because the hash code would change (at least under most implementations), so the hash table underlying the dictionary wouldn't be able to find even a reference to the same object that's already in there.
So your class would look something like this:
internal sealed class Element : IEquatable<Element>
{
private readonly int id;
public int Id { get { return id; } }
public Element(int id)
{
this.id = id;
}
public static implicit operator Element(int d)
{
return new Element(d);
}
public static bool operator ==(Element e1, Element e2)
{
if (object.ReferenceEquals(e1, e2))
{
return true;
}
if (object.ReferenceEquals(e1, null) ||
object.ReferenceEquals(e2, null))
{
return false;
}
return e1.id == e2.id;
}
public static bool operator !=(Element e1, Element e2)
{
// Delegate...
return !(e1 == e2);
}
public bool Equals(Element other)
{
return this == other;
}
public override int GetHashCode()
{
return id;
}
public override bool Equals(object obj)
{
// Delegate...
return Equals(obj as Element);
}
}
(I'm not sure about the merit of the implicit conversion, by the way - I typically stay away from those, myself.)
The Contains method does not use the == operator. What is the problem?
That is correct.
This method [Contains] determines equality by using the default equality comparer, as defined by the object's implementation of the IEquatable.Equals method for T (the type of values in the list).
http://msdn.microsoft.com/en-us/library/bhkz42b3(v=vs.110).aspx
You need to override Equals() as well. Note when you overload Equals(), it is almost always correct to also override GetHashCode().
Override Equals and GetHashCode like:
class Element
{
public int id;
protected bool Equals(Element other)
{
return id == other.id;
}
public override bool Equals(object obj)
{
if (ReferenceEquals(null, obj)) return false;
if (ReferenceEquals(this, obj)) return true;
if (obj.GetType() != this.GetType()) return false;
return Equals((Element) obj);
}
public override int GetHashCode()
{
return id; //or id.GetHashCode();
}
//..... rest of the class
See: List<T>.Contains Method
This method determines equality by using the default equality
comparer, as defined by the object's implementation of the
IEquatable<T>.Equals method for T (the type of values in the list).
Why does this program print "not added" while I think it should print "added"?
using System;
using System.Collections.Generic;
class Element
{
public int id;
public Element(int id)
{
this.id = id;
}
public static implicit operator Element(int d)
{
Element ret = new Element(d);
return ret;
}
public static bool operator ==(Element e1, Element e2)
{
return (e1.id == e2.id);
}
public static bool operator !=(Element e1, Element e2)
{
return !(e1.id == e2.id);
}
}
class MainClass
{
public static void Main(string[] args)
{
List<Element> element = new List<Element>();
element.Add(2);
if(element.Contains(2))
Console.WriteLine("added");
else
Console.WriteLine("not added");
}
}
The Contains method does not use the == operator. What is the problem?
The Contains method does not use the == operator
No - it uses Equals, which you haven't overridden... so you're getting the default behaviour of Equals, which is to check for reference identity instead. You should override Equals(object) and GetHashCode to be consistent with each other - and for sanity's sake, consistent with your == overload too.
I'd also recommend implementing IEquatable<Element>, which List<Element> will use in preference to Equals(object), as EqualityComparer<T>.Default picks it up appropriately.
Oh, and your operator overloads should handle null references, too.
I'd also strongly recommend using private fields instead of public ones, and making your type immutable - seal it and make id readonly. Implementing equality for mutable types can lead to odd situations. For example:
Dictionary<Element, string> dictionary = new Dictionary<Element, string>();
Element x = new Element(10);
dictionary[x] = "foo";
x.id = 100;
Console.WriteLine(dictionary[x]); // No such element!
This would happen because the hash code would change (at least under most implementations), so the hash table underlying the dictionary wouldn't be able to find even a reference to the same object that's already in there.
So your class would look something like this:
internal sealed class Element : IEquatable<Element>
{
private readonly int id;
public int Id { get { return id; } }
public Element(int id)
{
this.id = id;
}
public static implicit operator Element(int d)
{
return new Element(d);
}
public static bool operator ==(Element e1, Element e2)
{
if (object.ReferenceEquals(e1, e2))
{
return true;
}
if (object.ReferenceEquals(e1, null) ||
object.ReferenceEquals(e2, null))
{
return false;
}
return e1.id == e2.id;
}
public static bool operator !=(Element e1, Element e2)
{
// Delegate...
return !(e1 == e2);
}
public bool Equals(Element other)
{
return this == other;
}
public override int GetHashCode()
{
return id;
}
public override bool Equals(object obj)
{
// Delegate...
return Equals(obj as Element);
}
}
(I'm not sure about the merit of the implicit conversion, by the way - I typically stay away from those, myself.)
The Contains method does not use the == operator. What is the problem?
That is correct.
This method [Contains] determines equality by using the default equality comparer, as defined by the object's implementation of the IEquatable.Equals method for T (the type of values in the list).
http://msdn.microsoft.com/en-us/library/bhkz42b3(v=vs.110).aspx
You need to override Equals() as well. Note when you overload Equals(), it is almost always correct to also override GetHashCode().
Override Equals and GetHashCode like:
class Element
{
public int id;
protected bool Equals(Element other)
{
return id == other.id;
}
public override bool Equals(object obj)
{
if (ReferenceEquals(null, obj)) return false;
if (ReferenceEquals(this, obj)) return true;
if (obj.GetType() != this.GetType()) return false;
return Equals((Element) obj);
}
public override int GetHashCode()
{
return id; //or id.GetHashCode();
}
//..... rest of the class
See: List<T>.Contains Method
This method determines equality by using the default equality
comparer, as defined by the object's implementation of the
IEquatable<T>.Equals method for T (the type of values in the list).
I am making a wrapper for a "word" in an emulator project. Its meant to put all my cast conversions all in one spot. I was just about to start implement all the overrides for math functions (+,-,/,8, shift, etc.) When it occured to me that shouldn't all the implicit's take care of that? Do I need to over ride >= and <= when I got > < and ==?
I thought I would ask this as while there are plenty of questions relating to how to create them, there aren't many on how much is enough. Here is the code below:
public struct word_t
{
ulong val;
word_t(ulong val) { this.val = val; }
public static implicit operator word_t(int a) { return new word_t((ulong)a); }
public static implicit operator word_t(long a) { return new word_t((ulong)a); }
public static implicit operator word_t(uint a) { return new word_t((ulong)a); }
public static implicit operator word_t(ulong a) { return new word_t((ulong)a); }
public static implicit operator int(word_t a) { return (int)a.val; }
public static implicit operator long(word_t a) { return (long)a.val; }
public static implicit operator uint(word_t a) { return (uint)a.val; }
public static implicit operator ulong(word_t a) { return (ulong)a.val; }
public static bool operator ==(word_t a, word_t b) { return a.val == b.val; }
public static bool operator !=(word_t a, word_t b) { return a.val != b.val; }
public static bool operator >(word_t a, word_t b) { return a.val > b.val; }
public static bool operator <(word_t a, word_t b) { return a.val < b.val; }
public override bool Equals(object obj) {
return obj.Equals(val);
}
public override int GetHashCode() {
return val.GetHashCode();
}
public override string toString() {
return val.ToString();
}
}
My gut tells me to "Trust the compiler" but my head always worries on how efficient it is.
PS I just realized I should override shifts because of the bit shifting of negative number problems, but for right now just imagine shifts just magically work like adds between uint and int.
I recommend this MSDN article: http://msdn.microsoft.com/en-us/library/8edha89s(v=VS.100).aspx
It shows the operators you can overload and any catches. You can overload <= and >= but they must be overloaded in pairs, as is true with == and != as well.
The complex match operators +=, etc are available if +, etc. is overloaded, etc.
>= and <=, however, are separate. That is, overloading > and == does not give you a >= operator implicitly.
I have a lot of functions which are currently overloaded to operate on int and string:
bool foo(int);
bool foo(string);
bool bar(int);
bool bar(string);
void baz(int p);
void baz(string p);
I then have a lot of functions taking 1, 2, 3, or 4 arguments of either int or string, which call the aforementioned functions:
void g(int p1) { if(foo(p1)) baz(p1); }
void g(string p1) { if(foo(p1)) baz(p1); }
void g(int p2, int p2) { if(foo(p1)) baz(p1); if(bar(p2)) baz(p2); }
void g(int p2, string p2) { if(foo(p1)) baz(p1); if(bar(p2)) baz(p2); }
void g(string p2, int p2) { if(foo(p1)) baz(p1); if(bar(p2)) baz(p2); }
void g(string p2, string p2) { if(foo(p1)) baz(p1); if(bar(p2)) baz(p2); }
// etc.
Note: The implementation of the g() family is just an example
More types than the current int or string might be introduced at any time. The same goes for functions with more arguments than 4. The current number of identical functions is barely manageable. Add one more variant in either dimension and the combinatoric explosion will be so huge, it might blow away the application.
In C++, I'd templatize g() and be done.
I understand that .NET generics are different. I have been fighting them for two hours now trying to come up with a solution that doesn't involve copy and pasting code, to no avail.
C# generics won't require me to type out identical code for a family of functions taking five arguments of either of three types?
What am I missing?
Edit: These functions are used to parse a bunch of arguments (currently either int or string) from some source. Imagine bar() and baz() being able to read both int or string, and the g() family specifying the type and number of arguments to parse (implicitly, by their arguments' types).
Consider using inheritance for this case. I am assuming that foo, bar and baz are inherent to the type (int or string in your case). If this is not true please correct or comment this answer.
using System;
namespace ConsoleApplication3
{
abstract class Param
{
public abstract bool Foo();
public abstract bool Bar();
public abstract void Baz();
public static IntParam Create(int value)
{
return new IntParam(value);
}
public static StringParam Create(string value)
{
return new StringParam(value);
}
}
abstract class Param<T> : Param {
private T value;
protected Param() { }
protected Param(T value) { this.value = value; }
public T Value {
get { return this.value; }
set { this.value = value; }
}
}
class IntParam : Param<int>
{
public IntParam() { }
public IntParam(int value) : base(value) { }
public override bool Foo() { return true; }
public override bool Bar() { return true; }
public override void Baz()
{
Console.WriteLine("int param value is " + this.Value);
}
}
class StringParam : Param<string>
{
public StringParam() { }
public StringParam(string value) : base(value) { }
public override bool Foo() { return true; }
public override bool Bar() { return true; }
public override void Baz()
{
Console.WriteLine("String param value is " + this.Value);
}
}
class Program
{
static void g(Param p1)
{
if (p1.Foo()) { p1.Baz(); }
}
static void g(Param p1, Param p2)
{
if (p1.Foo()) { p1.Baz(); }
if (p2.Bar()) { p2.Baz(); }
}
static void Main(string[] args)
{
Param p1 = Param.Create(12);
Param p2 = Param.Create("viva");
g(p1);
g(p2);
g(p1, p1);
g(p1, p2);
g(p2, p1);
g(p2, p2);
Console.ReadKey();
}
}
}
This would output:
int param value is 12
String param value is viva
int param value is 12
int param value is 12
int param value is 12
String param value is viva
String param value is viva
int param value is 12
String param value is viva
String param value is viva
For a new supported type you:
create a new class that supports the type and extends Param<T>;
implement Foo, Bar and Baz for that new type;
Create a new g method (just one) that has another parameter.
Specially for 3) this would greatly reduce explosion of methods. Now you write a single g method for any given number of parameters. With previous design you had to write, for n parameters, 2^n methods (n = 1 -> 2 methods, n = 2 -> 4 methods, n = 3 -> 8 methods, ..).
Your true problem here is most likely one of design, rather than something generics can be used for. Generics should be used for things that are actually type-agnostic, not as a catch-all to make life a bit easier. Perhaps try posting some actual example code you're using, and someone may have an idea about how to redesign your solution in a way that will allow you to extend it without so much headache.
As a teaser, consider something like this:
public void DoSomethingConditionally<T>(T key, Func<T, bool> BooleanCheck, Action<T> WhatToDo)
{
if (BooleanCheck(key)) WhatToDo(key);
}
And you could call it like this:
DoSomethingConditionally<String>("input", v => v == "hello", s => Console.WriteLine(s));
I've used lambda expressions here, but you could just as easily predefine a few Func<>s that perform some common expressions. This would be a much better pattern than method overloading, and would force you to handle new input types at design time.
Not as optimal as I would like... but what if foo, bar, and baz had generic versions as well?
static bool foo(int input)
{
return input > 5;
}
static bool foo(string input)
{
return input.Length > 5;
}
static void baz(int input)
{
Console.WriteLine(input);
}
static void baz(string input)
{
Console.WriteLine(input);
}
static bool foo<T>(T input)
{
if (input is int) return foo((int)(object)input);
if (input is string) return foo((string)(object)input);
return false;
}
static void baz<T>(T input)
{
if (input is int) baz((int)(object)input);
else if (input is string) baz((string)(object)input);
else throw new NotImplementedException();
}
static void g<T>(T input)
{
if (foo(input))
baz(input);
}
static void g<T, U>(T input, U inputU)
{
g(input);
g(inputU);
}
Use a list of objects.
In the case the number of parameters are unknown at planning time, just use a list of objects. Something like:
void g(params object[] args) {
foreach (object arg in args) {
if ((arg is int) && (foo((int)arg))) baz((int)arg) else
if ((arg is string) && (foo((string)arg))) baz((string)arg)
}
}
(Assuming you have bool foo(int), bool foo(string)...)
So you can call:
g(p1, p2);
g(p1);
g(p1, p2, p3)
with any combination of the types, since every reference derives from object (which it could be many more types than required, int and string, but could be handy in future to support more other types).
This is possible since you could use Reflection to recognize the type at runtime.
Another way to execute a sequence of operation is the use of interfaces, defining the action to execute at certain conditions, on certain objects.
interface IUpdatable {
void Update(object[] data);
}
class object1 : IUpdatable { public void Update(object data) { baz(data); } }
class object2 : IUpdatable { public void Update(object data) { baz(data); } }
void g(params IUpdatable[] args) {
foreach (IUpdatable arg in args) {
arg.Update(args);
}
}
But this way you have to model p1 and p2 (but also p3, as objects implementing an interface, which could be not possible.
I would have done this as a comment to #smink, but I don't have enough rep...
If you extend the Param base class to have implicit operators you are back to not having to wrap the contents in code (though the runtime still incurs the wrapping overhead)...
abstract class Param
{
...
public static implicit operator Param(int value)
{ return new IntParam(value); }
}
If you are using C# / .NET 4.0, you can achieve multiple dispatch using the dynamic feature so you only have to implement a single overload of g based on the number of arguments and the proper foo/bar/baz overloads by type inside each g implementation will be resolved at runtime.
void g(dynamic p1) { if (foo(p1)) baz(p1); }
void g(dynamic p1, dynamic p2) { if (foo(p1)) baz(p1); if (bar(p2)) baz(p2); }
Edit:
Even though you are unable to use C# / .NET 4.0, you can still use this approach using reflection. I've added another foo/bar/baz overload for double showing how well this generalizes and allows you to eliminate duplicate g implementations.
bool foo(int p) {Console.WriteLine("foo(int)=" + p); return p == 0;}
bool foo(string p) {Console.WriteLine("foo(string)=" + p); return p == "";}
bool foo(double p) { Console.WriteLine("foo(double)=" + p); return p == 0.0; }
bool bar(int p) {Console.WriteLine("bar(int)=" + p); return p == 1;}
bool bar(string p) { Console.WriteLine("bar(string)=" + p); return p == ""; }
bool bar(double p) { Console.WriteLine("bar(double)=" + p); return p == 1.1; }
void baz(int p) {Console.WriteLine("baz(int)=" + p);}
void baz(string p) { Console.WriteLine("baz(string)=" + p); }
void baz(double p) { Console.WriteLine("baz(double)=" + p); }
//these object overloads of foo/bar/baz allow runtime overload resolution
bool foo(object p)
{
if(p == null) //we need the type info from an instance
throw new ArgumentNullException();
//may memoize MethodInfo by type of p
MethodInfo mi = typeof(Program).GetMethod(
"foo",
BindingFlags.Instance | BindingFlags.InvokeMethod | BindingFlags.NonPublic,
null,
new Type[] { p.GetType() },
null
);
if (mi.GetParameters()[0].ParameterType == typeof(object))
throw new ArgumentException("No non-object overload found");
return (bool)mi.Invoke(this, new object[] { p });
}
bool bar(object p)
{
if (p == null)
throw new ArgumentNullException();
MethodInfo mi = typeof(Program).GetMethod(
"bar",
BindingFlags.Instance | BindingFlags.InvokeMethod | BindingFlags.NonPublic,
null,
new Type[] { p.GetType() },
null
);
if (mi.GetParameters()[0].ParameterType == typeof(object))
throw new ArgumentException("No non-object overload found");
return (bool)mi.Invoke(this, new object[] { p });
}
void baz(object p)
{
if (p == null)
throw new ArgumentNullException();
MethodInfo mi = typeof(Program).GetMethod(
"baz",
BindingFlags.Instance | BindingFlags.InvokeMethod | BindingFlags.NonPublic,
null,
new Type[] { p.GetType() },
null
);
if (mi.GetParameters()[0].ParameterType == typeof(object))
throw new ArgumentException("No non-object overload found");
mi.Invoke(this, new object[] { p });
}
//now you don't need to enumerate your identical implementations of g by type
void g(object p1) { if (foo(p1)) baz(p1); }
void g(object p1, object p2) { if (foo(p1)) baz(p1); if (bar(p2)) baz(p2); }
Unfortunately, generics cannot handle this situation. At least, not well. If you make your methods generic, then just about any type can be passed into them. There won't be an adequate where clause on the generics to limit it to just string and int. If your methods are going to do specific int/string related operations inside them, then generics wont work at all.
Generics in C# are not nearly as powerful as templates in C++, and yes they can cause some major headaches at time. It just takes time to get used to them and get a feel for what they can and cannot do.
This might be a bit heavy handed, but would encapsulating the different parameters types as classes work?:
public abstract class BaseStuff
{
public abstract bool Foo();
public abstract bool Bar();
public abstract void Baz();
public void FooBaz()
{
if(Foo()) Baz();
}
public void BarBaz()
{
if(Bar()) Baz();
}
}
public class IntStuff : BaseStuff
{
private int input;
public IntStuff(int input)
{
this.input = input;
}
public bool Foo()
{
//logic using input for example
return input > 0;
}
//implement Bar and Baz using input
}
public class StringStuff : BaseStuff
{
private string input;
public IntStuff(string input)
{
this.input = input;
}
//Implement Foo, Bar and Baz
}
And then have some G methods somewhere:
public void G(BaseStuff stuff1)
{
stuff1.FooBaz();
}
public void G(BaseStuff stuff1, BaseStuff stuff2)
{
stuff1.FooBaz();
stuff2.BarBaz();
}
And you can then call with:
G(new IntStuff(10), new StringStuff("hello"));
G(new StringStuff("hello"), new StringStuff("world"));
You can use code generation to solve this.
Look at Reflection.Emit. You can also generate code with T4 in Visual Studio.
The types are really getting in the way here. You could also try to solve this with a dynamic language or with the C# 4 dynamic keyword.
If you are using c# 4.0 you can do this with the option parameter
Or you can use object
Foo(object o)
{
if (o is int){ }
else if (o is string){ }
}
Or you can use the generic method Foo<T>(T o){ }