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Generic Class Polymorphisim

If I have the following:
public abstract class Parameter<T>
{
protected T value;
public virtual T Value
{
get { return value; }
set { this.value = value; }
}
protected Parameter(T startingValue)
{
value = startingValue;
}
}
public class FloatParameter : Parameter<float>
{
public FloatParameter(float startingValue) : base(startingValue){}
}
public class IntParameter : Parameter<int>
{
public override int Value
{
get { return value; }
set { this.value = value > 100 ? 100 : value; }
}
public IntParameter(int startingValue) : base (startingValue) {}
}
Is there any way to create some List<Parameter> that can contain any of the derived types? For example, something like:
// no type specified in Parameter
List<Parameter> storedParameters = new List<Parameter>();
storedParameters.Add(new FloatParameter(2f));
storedParameters.Add(new IntParameter(7));
foreach(Parameter p in storedParameters)
{
DoSomethingWithValue(p.Value);
}
Or, alternatively, if this implementation is flawed, is there a better way to do this? What I have here feels slightly naive.

The only way I see to manage such case is to have and Interface that you use to manage the generic types, something like this should work:
public interface IParameter
{
void DoSomething();
}
public abstract class Parameter<T>
{
protected T value;
public T Value
{
get { return value; }
set { this.value = value; }
}
protected Parameter(T startingValue)
{
value = startingValue;
}
}
public class FloatParameter : Parameter<float>, IParameter
{
public FloatParameter(float startingValue) : base(startingValue) { }
public void DoSomething()
{
Console.WriteLine(value);
}
}
public class IntParameter : Parameter<int>, IParameter
{
public IntParameter(int startingValue) : base(startingValue) { }
public void DoSomething()
{
Console.WriteLine(value);
}
}
Ont his case you would be able to create a List of the Interface IParameter and add there specific instances:
var list = new List<IParameter>();
list.Add(new FloatParameter(1F));
list.Add(new IntParameter(1));
foreach (var item in list)
{
item.DoSomething();
}

Try to add nongeneric interface. Here is an example:
public class Program
{
static void Main(string[] args)
{
try
{
List<IParameter> storedParameters = new List<IParameter>();
storedParameters.Add(new FloatParameter(2f));
storedParameters.Add(new IntParameter(7));
foreach (IParameter p in storedParameters)
{
Console.WriteLine(p.ToString());
}
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
}
public interface IParameter
{
object value { get; }
}
public class Parameter<T> : IParameter
{
public object value { get; protected set; }
public virtual T Value
{
get { return (T)value; }
set { this.value = value; }
}
protected Parameter(T startingValue)
{
value = startingValue;
}
}
public class FloatParameter : Parameter<float>
{
public FloatParameter(float startingValue) : base(startingValue){ }
}
public class IntParameter : Parameter<int>
{
public override int Value
{
get { return (int)value; }
set { this.value = value > 100 ? 100 : value; }
}
public IntParameter(int startingValue) : base (startingValue) { }
}

No, it's not possible to do it.
What you are trying to do is to have an interface (or base class) that expose a property of an undefined type, to be able to then retrieve that value and dispatch it dynamically to the proper override of DoSomethingWithValue.
What you are after is achievable defining the property as dynamic, instead of using generics.
public class Parameter
{
protected dynamic value;
public dynamic Value
{
get { return value; }
set { this.value = value; }
}
public Parameter(dynamic startingValue)
{
value = startingValue;
}
}
public class MyStuff {
public void DoStuff()
{
List<Parameter> storedParameters = new List<Parameter>();
storedParameters.Add(new Parameter(2f));
storedParameters.Add(new Parameter(7));
foreach (Parameter p in storedParameters)
{
DoSomethingWithValue(p.Value);
}
}
}
Otherwise you should look into implementing a Double dispatch.

You can do it by defining a common interface and using the visitor pattern.
public interface IParameterVisitor
{
void VisitInt(int value);
void VisitFloat(float value);
}
public interface IParameter
{
void Accept(IParameterVisitor visitor);
}
The previous implementation has to be modified a bit:
public abstract class Parameter<T> : IParameter
{
protected T value;
public virtual T Value
{
get { return value; }
set { this.value = value; }
}
protected Parameter(T startingValue)
{
value = startingValue;
}
public abstract void Accept(IParameterVisitor visitor);
}
FloatParameter will VisitFloat, and IntParameter will VisitInt
public class FloatParameter : Parameter<float>
{
public FloatParameter(float startingValue) : base(startingValue) { }
public override void Accept(IParameterVisitor visitor)
{
visitor.VisitFloat(this.value);
}
}
public class IntParameter : Parameter<int>
{
public override int Value
{
get { return value; }
set { this.value = value > 100 ? 100 : value; }
}
public override void Accept(IParameterVisitor visitor)
{
visitor.VisitInt(this.value);
}
public IntParameter(int startingValue) : base(startingValue) { }
}
And our visitor for example:
public class MyVisitor : IParameterVisitor
{
public void VisitInt(int value)
{
Console.WriteLine($"Visiting an int: {value}");
}
public void VisitFloat(float value)
{
Console.WriteLine($"Visiting a float: {value}");
}
}
Finally, the usage:
var parameters =
new List<IParameter> {new FloatParameter(0.5f), new IntParameter(1)};
var visitor = new MyVisitor();
foreach (IParameter parameter in parameters) {
parameter.Accept(visitor);
}

If you change the value to an object you will be able to set the value to whatever type you like:
class Program
{
static void Main(string[] args)
{
// no type specified in Parameter
var storedParameters = new List<ParameterBase>();
storedParameters.Add(new FloatParameter(3.5F));
storedParameters.Add(new IntParameter(7));
foreach (var p in storedParameters)
{
Console.WriteLine(p.Value);
}
}
}
public class ParameterBase
{
protected object value;
public virtual object Value
{
get { return value; }
set { this.value = value; }
}
}
public class FloatParameter : ParameterBase
{
public FloatParameter(float value)
{
Value = value;
}
}
public class IntParameter : ParameterBase
{
public IntParameter(int value)
{
Value = value;
}
}
UPDATED: Use object instead of dynamic and removed ValueType as suggested by #Pieter Witvoet

How can I pass value from one subclass to another subclass in a main class C#?

I create a class named MyMainClass
namespace MyTest
{
private void frmMain_Load(object sender, EventArgs e)
{
MyMainClass myVar = new MyMainClass();
myVar.sub1.sb1A = "value 1A";
myVar.sub1.sb1B = "value 1B";
MessageBox.Show(myVar.sub2.wantPassString);
//I want to print the value "I've got value value 1A"
}
public class MyMainClass
{
public subClass1 sub1 = new subClass1();
public subClass2 sub2 = new subClass2();
public class subClass1
{
public string sb1A{get;set;}
public string sb1B{get;set;}
}
public class subClass2
{
public string sb2A{get;set;}
public string sb2B{get;set;}
// a1a is a value that I want to get from subClass1
string a1a = subClass1.sb1A;
public string wantPassString {get{return "I've got value " + a1a;}}
}
}
}
How can I pass the value from subClass1.sb1A to the string a1a or wantPassString in subClass2 ? when I call in frmMain_Load

The normal approach would be to pass the class through the constructor. This works:
public class MyMainClass
{
public MyMainClass()
{
sub1 = new subClass1();
sub2 = new subClass2(sub1);
}
public subClass1 sub1;
public subClass2 sub2;
public class subClass1
{
public string sb1A{get;set;}
public string sb1B{get;set;}
}
public class subClass2
{
public subClass2(subClass1 sub1)
{
this.sub1 = sub1;
}
public string sb2A{get;set;}
public string sb2B{get;set;}
subClass1 sub1;
public string wantPassString {get{return "I've got value " + sub1.sb1A;}}
}
}

Create a third class to hold the data.
public MainClass
{
private class sharedClass
{
internal string sb1A { get; set; }
}
public class subClass1
{
private readonly sharedClass _shared;
internal subClass1(sharedClass shared)
{
this._shared = shared;
}
public string sb1A
{
get
{
return this._shared.sb1A;
}
set
{
this._shared.sb1A = value;
}
public string sb1B{get;set;}
}
public class subClass2
{
private readonly sharedClass _shared;
public subClass2(shared s)
{
_shared = s;
}
public string sb2A{get;set;}
public string sb2B{get;set;}
public string wantPassString {get{return "I've got value " + _shared.sb1;}}
}
private readonly sharedClass _shared = new sharedClass();
private readonly subClass1 _subClass1;
private readonly subClass2 _subClass2;
public MainClass()
{
this._subClass1 = new subClass1(this._shared);
this._subClass2 = new subClass2(this._shared);
}
}

You can add additional property and method and pass it as a parameter:
public string sb2C{ get; set; }
public string getData(string strParam)
{
return sb2C= strParam;
}
Then on your frmMain_Load:
MessageBox.Show(myVar.sub2.getData(myVar.sub1.sb1B));
//This would also populate sb2C that will hold the data from the other class

Avoid having to cast with generics and a list of custom data

I have the following code for supporting a list of different types :
public enum eType
{
tInt,
tString,
tDateTime
}
public interface ICustomType<out T>
{
T Value { get; }
}
public abstract class DifferentType
{
protected DifferentType(eType type, string mnemonic)
{
Type = type;
Mnemonic = mnemonic;
}
public string Mnemonic { get; private set; }
public eType Type { get; private set; }
}
public class DateTimeType : DifferentType, ICustomType<DateTime>
{
public DateTimeType(DateTime value, string mnemonic)
: base(eType.tDateTime, mnemonic)
{
Value = value;
}
public DateTime Value { get; private set; }
}
public class IntType : DifferentType, ICustomType<int>
{
public IntType(int value, string mnemonic)
: base(eType.tInt, mnemonic)
{
Value = value;
}
public int Value { get; private set; }
}
public class StringType : DifferentType, ICustomType<string>
{
public StringType(string value, string mnemonic)
: base(eType.tString, mnemonic)
{
Value = value;
}
public string Value { get; private set; }
}
public static class UtilValue
{
public static T GetValue<T>(DifferentType customType)
{
return ((ICustomType<T>)customType).Value;
}
}
public class testTypes2
{
public testTypes2()
{
var values = new List<DifferentType> { GetInt(), GetString(), GetDate() };
foreach (var i in values)
{
switch (i.Type)
{
case eType.tInt:
int resInt = UtilValue.GetValue<int>(i);
break;
case eType.tString:
string resString = UtilValue.GetValue<string>(i);
break;
case eType.tDateTime:
DateTime resDateTime = UtilValue.GetValue<DateTime>(i);
break;
}
}
}
private DateTimeType GetDate()
{
return new DateTimeType(new DateTime(2000, 1, 1), "MnemonicDate");
}
private IntType GetInt()
{
return new IntType(5, "MnemonicInt");
}
private StringType GetString()
{
return new StringType("ok", "MnemonicString");
}
}
and would like to avoid the cast at line return ((ICustomType<T>)customType).Value; in the UtilValue class, any idea how I can get rid of that while still keeping the design?
I am not even sure if this cast is expensive to do? My guess is most certainly.

Visitor-pattern example:
interface IDifferentTypeVisitor
{
void Visit(DateTimeType dt);
void Visit(StringType st);
}
class DifferentType
{
public abstract void Accept(IDifferentTypeVisitor visitor);
}
class DateTimeType : DifferentType
{
public void Accept(IDifferentTypeVisitor visitor)
{
visitor.Visit(this);
}
}
class StringType : DifferentType
{
public void Accept(IDifferentTypeVisitor visitor)
{
visitor.Visit(this);
}
}
class SomeVisitor : IDifferentTypeVisitor
{
public void Visit(DateTimeType dt)
{
//DateTime resDateTime = dt.Value; Or similar
}
public void Visit(StringType st)
{
//string resString = st.Value; Or similar
}
}
public class testTypes2
{
public testTypes2()
{
var values = new List<DifferentType> { /* Content */ };
var visitor = new SomeVisitor();
foreach (var i in values)
{
i.Accept(visitor);
}
}
}
In C# 4 with dynamic it's possible to save some code by adding this to DifferentType:
public void Accept(IDifferentTypeVisitor visitor)
{
visitor.Visit((dynamic)this);
}
and then delete all other Accept methods. It hurts performance but it looks better ;-)

Instantiating a class given a generic abstract type

Using this model:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace ConsoleApplication1
{
#region Abstracts definitions
abstract class AnAbstract
{
public string Name { get { return this.GetType().Name; } }
public bool IsNumeric { get { return this is ANumericAbstract; } }
public /*abstract*/ string Description = default(string);
}
abstract class ANumericAbstract : AnAbstract
{
public /*abstract*/ double Min = double.MinValue;
public /*abstract*/ double Max = double.MaxValue;
}
abstract class ANonNumericAbstract : AnAbstract
{
public List<Object> objects = new List<Object>();
}
#endregion Abstracts definitions
#region Concrete definitions
class NumericImpl : ANumericAbstract
{
new public const string Description = "A numeric implementation";
new public const double Min = 0;
new public const double Max = 1000;
public NumericImpl()
{
}
}
abstract class AnotherImpl : ANonNumericAbstract
{
public AnotherImpl()
{
objects.Add("one");
objects.Add("two");
objects.Add("three");
}
}
class SideA : AnotherImpl
{
new public const string Description = "Disc side A";
}
class SideB : AnotherImpl
{
new public const string Description = "Disc side B";
}
#endregion Concrete definitions
partial class Parameter
{
public string Name { get; set; }
public string Description { get; set; }
public bool IsNumeric { get; private set; }
public double Min { get; private set; }
public double Max { get; private set; }
public List<Object> Values { get; private set; }
private Parameter()
{
Values = new List<Object>();
}
}
}
With this, I pretend to define a hierarchy of classes for which I can have some abstract properties (Name,Description,IsNumeric) and at the end of the hierarchy there should be some classes which mandatorily define those properties; in the case of ANumericAbstract they should have additional specific properties, e.g. Min and Max.
Now here's the problem.
I'm attemtping to be able to create instances of Parameter which take a generic AnAbstract and read from it some values to fill in the Parameter properties, à la
Parameter<ANumericAbstract> ParamNum = new Parameter<NumericImpl>();
where a Parameter constructor would take in the passed type and "fill in the blanks". In other words, I'm trying something like:
using System;
namespace ConsoleApplication1 {
partial class Parameter
{
public static Parameter NewParameter<T>() where T : AnAbstract
{
Parameter Parameter = new Parameter();
// THESE DON'T WORK:
this.Name = T.Name;
this.Description = T.Description;
this.IsNumeric = T.IsNumeric;
if (this.IsNumeric)
{
this.Min = (T as ANumericAbstract).Min;
this.Max = (T as ANumericAbstract).Max;
}
else
{
foreach(Object val in (T as ANonNumericAbstract).Values)
{
this.Values.Add(val);
}
}
return Parameter;
}
}
class Program
{
private AnAbstract Number = new NumericImpl();
static void Main(string[] args)
{
}
// THESE DON'T WORK:
private static Parameter<ANumericAbstract> ParameterNum =
Parameter.NewParameter<NumericImpl>();
private static Parameter<ANonNumericAbstract> ParameterA =
Parameter.NewParameter<SideA>();
private static Parameter<ANonNumericAbstract> ParameterB =
Parameter.NewParameter<SideB>();
}
}
Obviously the syntax is invalid, but I'm not sure if I'm going in the right direction. Is there some Generics syntax that I'm not using properly? Should I just be done with it and use Getters and Setters à la Java? :-) At this point, just doing the
Parameter par = new Parameter { Name = NumericImpl.Name, /* ... */ };
might seem more sensible...

Firstly you should not use New keyword on your properties.
Consider virtual keyword:
abstract class AnAbstract
{
public virtual string Name { get { return this.GetType().Name; } }
public virtual string Description { get { return String.Empty; } }
}
abstract class ANumericAbstract : AnAbstract
{
public virtual double Min = double.MinValue;
}
class NumericImpl : ANumericAbstract
{
public override string Description { get { return "A numeric implementation"; } }
public override double Min { get { return 0; } }
}
1) You can place an instance of you type in Parameter constructor and have Parameter instance.
partial class Parameter
{
public Parameter(AnAbstract inputObject)
{
this.Name = inputObject.Name;
// etc
}
}
private static Parameter ParameterNum = new Parameter(new NumericImpl());
2) The second way is to use reflection to create an instance of object with initial parameters.
partial class Parameter<T> where T : AnAbstract
{
public static Parameter<T> NewParameter<T>() where T : AnAbstract
{
Parameter<T> parameter = new Parameter<T>();
AnAbstract instance = (AnAbstract)Activator.CreateInstance(typeof(T));
parameter.Name = instance.Name;
// etc
return parameter;
}
}
private static Parameter<NumericImpl> ParameterNum =
Parameter<NumericImpl>.NewParameter();
3) Make Parameter class static and create in via static constructor.
static partial class Parameter<T> where T : AnAbstract
{
public static string Name { get; set; }
//etc
}
static partial class Parameter<T> where T : AnAbstract
{
static Parameter ()
{
AnAbstract instance = (AnAbstract)Activator.CreateInstance(typeof(T));
Parameter<T>.Name = instance.Name;
//etc
}
}
In the last example you can use this class like this:
String someName = Parameter<NumericImpl>.Name;

Variable class properties due to specific constructor in C#

Suppose class A as:
public class A
{
private string _str;
private int _int;
public A(string str)
{
this._str = str;
}
public A(int num)
{
this._int = num;
}
public int Num
{
get
{
return this._int;
}
}
public string Str
{
get
{
return this._str;
}
}
}
I want to hide Str property when i construct class A as
new A(2)
and want to hide Num property when i construct class A as
new A("car").
What should i do?

That isn't possible with a single class. An A is an A, and has the same properties - regardless of how it is constructed.
You could have 2 subclasses of abstract A, and a factory method...
public abstract class A
{
class A_Impl<T> : A
{
private T val;
public A_Impl(T val) { this.val = val; }
public T Value { get { return val; } }
}
public static A Create(int i) { return new A_Impl<int>(i); }
public static A Create(string str) { return new A_Impl<string>(str); }
}
But : the caller will not know about the value unless they cast it.

use generics
public class A<T>
{
private T _value;
public A(T value)
{
this._value= value;
}
public TValue
{
get
{
return this._value;
}
}
}