Please excuse bursts of stupidity as I learn the intricacies of C# / .NET
Say I have three classes with multiple static properties (more than three but for arguments sake..)
CLASS FOO
public static A
{
get / set A;
}
public static B
{
get / set B;
}
public static C
{
get / set C;
}
CLASS BAR
{
get / set A;
}
public static B
{
get / set B;
}
public static C
{
get / set C;
}
CLASS YOO
{
get / set A;
}
public static B
{
get / set B;
}
public static C
{
get / set C;
}
And from another class I need to update one or several static properties in each class multiple times... How do I keep from writing multiple SWITCH statments like this...
public void updateVarx(string class, string varx)
{
string y = 'class'
SWITCH (y)
{
case FOO:
FOO.A = Varx;
break;
case BAR:
BAR.A = Varx;
break;
case YOO:
YOO.A = Varx;
break;
}
}
And then another one when I want to update B varY:
public void updateVary(string class, string vary)
{
string y = 'class'
SWITCH (y)
{
case FOO:
FOO.B = Vary;
break;
case BAR:
BAR.B = Vary;
break;
case YOO:
YOO.B = Vary;
break;
}
}
Since you are learning .net/c#, I guess i should warn you, using static properties is probably not the way to go in object oriented programming.
Static is global state and is dangerous. If you end up using multi-threaded code, you have to be super careful. If you need only one instance, just instantiate one, but don't go creating static properties on a class, unless you have a pretty good reason to add them (And I can't think of any right now).
In fact, in well designed, object oriented code you sould probably not have many if, switch, getters or setters either.
Let's say you need different behaviors on your classes, you can do it this way.
Interface ISecurity {
void UpdateVarX(int value);
void UpdateVarY(int value);
int GetValueX();
int GetValueX();
}
class Foo:ISecurity {
// Implement methods of the interface
}
class Bar:ISecurity {
// Implement methods of the interface
}
class Yoo:ISecurity {
// Implement methods of the interface
}
// This class is the class that uses your other classes
class Consumer
{
private ISecurity sec;
public Consumer(ISecurity sec) {
sec.UpdateVarX(25);
}
}
Or if as in your example, all your static classes have the same properties:
public class Settings {
public int A {get; set;}
public int B {get; set;}
public int C {get; set;}
}
public class NeedsToUseOtherClass {
public NeedsToUseOtherClass() {
Settings foo = new Settings();
Settings bar = new Settings();
Settings yoo = new Settings();
foo.setA(25);
}
}
Maybe I am not understanding the problem but if all your classes have the same exact properties then you can just pass the object (FOO, BAR, or YOO) into UpdateVarx or UpdateVary methods and just implement an interface? Something along these lines:
public class FOO : IHasStatus
{
public A
{
get / set A;
}
public B
{
get / set B;
}
public C
{
get / set C;
}
}
public void updateVarx(IHasStatus someObject, string varx)
{
someObject.A = varx;
}
public void updateVary(IHasStatus someObject, string vary)
{
someObject.B = vary;
}
If you don't need the concrete classes, you can abstract out the logic like so:
public class Status {
public string A {
get; set;
}
public string B {
get; set;
}
public string C {
get; set;
}
}
public static class StatusManager {
private static Dictionary<string, Status> statusMap = new Dictionary<string,Status>();
public static Status GetStatus(string name) {
Status status;
if (!statusMap.TryGetValue(name, out status))
statusMap[name] = status = new Status();
return status;
}
public static void SetStatus(string name, Status status) {
statusMap[name] = status;
}
public static void UpdateVarx(string name, string varx) {
GetStatus(name).A = varx;
}
// ...
}
If you are a fan of the javascript way of solving multiple switch cases like this
you can always wrap up the switch handlers as Actions and toss them in a Dictionary.
For example : (Source obtained from here)
public class SwitchCase : Dictionary<string,Action>
{
public void Eval(string key)
{
if (this.ContainsKey(key))
this[key]();
else
this["default"]();
}
}
//Now, somewhere else
var mySwitch = new SwitchCase
{
{ "case1", ()=>Console.WriteLine("Case1 is executed") },
{ "case2", ()=>Console.WriteLine("Case2 is executed") },
{ "case3", ()=>Console.WriteLine("Case3 is executed") },
{ "case4", ()=>Console.WriteLine("Case4 is executed") },
{ "default",()=>Console.WriteLine("Default is executed") },
};
mySwitch.Eval(c);
Below code uses all kinds of hacks, not really recommended in production code unless you have a very good reason.
using System;
using System.Linq;
namespace ConsoleApplication1
{
static class Program
{
private static void SetStaticProperty(string className, string propName, string varx)
{
//This sucks, I couldnt find the namespace with easily through reflection :(
string NAMESPACE = "ConsoleApplication1";
Type t = Type.GetType(NAMESPACE + "." + className);
t.GetProperties().Where(p => p.Name == propName).First().SetValue(null, varx, null);
}
public static void updateVarx(string className, string varx)
{
SetStaticProperty(className, "A", varx);
}
public static void updateVary(string className, string vary)
{
SetStaticProperty(className, "B", vary);
}
static void Main(string[] args)
{
updateVarx("Foo", "FooAstring");
updateVarx("Bar", "BarAstring");
updateVarx("Yod", "YodAstring");
updateVary("Foo", "FooBstring");
updateVary("Bar", "BarBstring");
updateVary("Yod", "YodBstring");
Console.WriteLine(Foo.A);
Console.WriteLine(Foo.B);
Console.WriteLine(Bar.A);
Console.WriteLine(Bar.B);
Console.WriteLine(Yod.A);
Console.WriteLine(Yod.B);
Console.ReadLine();
}
}
class Foo
{
public static string A { get; set; }
public static string B { get; set; }
public static string C { get; set; }
}
class Bar
{
public static string A { get; set; }
public static string B { get; set; }
public static string C { get; set; }
}
class Yod
{
public static string A { get; set; }
public static string B { get; set; }
public static string C { get; set; }
}
}
You can use dictionary as configuration and remove the switch statement
Create a dictionary and add append data as below for mapping
//Have dictionary setted up
Dictionary<string, dynamic> m_Dictionary = new Dictionary<string, dynamic>();
m_xmlDictionary.Add("classA",FOO);
m_xmlDictionary.Add("classB",BAR);
m_xmlDictionary.Add("classC",BAR);
//Have dictionary setted up
//change the function as below
public void updatevarx(string class, string varx)
{
m_Dictionary[class].A=varx // Replaced switch statement
}
//while calling use
updatevarx("classC","abc!");// This will assign BAR.A with abc!
Related
I want to create a class with a property that "variably" points to some other property in another class.
Imagine a class (called "Limiter") with several integer properties (Limit1, Limit2, etc).
I now want a second class ("LimitWatcher") which can "watch" one of those limits. But I want to be able to set which particular limit it is watching in the constructor. I eventually want several instances of LimitWatcher, each one pointing to a separate Limit. The Limit values themselves may change after the Watchers have been instantiated, but the watcher must always see the current value of the Limit that it is watching. So basically, I want to store a reference to an integer.
I know I can accomplish this using reflection (see example below), but I feel as though there might be a simpler way.
using System;
namespace ConsoleApplication4
{
public class Limiter
{
public int limit1 { get; set; } = 10;
public int limit2 { get; set; } = 20;
public void Update()
{
limit1++;
limit2++;
}
}
public class LimitWatcher
{
public LimitWatcher(Limiter lim, string propName)
{
myLimiter = lim;
limitName = propName;
}
private Limiter myLimiter { get; }
public string limitName { get; set; }
//can I do this without reflection:
public int FooLimit { get { return (int)typeof(Limiter).GetProperty(limitName).GetValue(myLimiter); } }
}
class Program
{
static void Main(string[] args)
{
Limiter lim = new ConsoleApplication4.Limiter();
LimitWatcher w1 = new LimitWatcher(lim, nameof(lim.limit1));
LimitWatcher w2 = new LimitWatcher(lim, nameof(lim.limit2));
lim.Update();
Console.WriteLine($"1st watcher sees {w1.FooLimit}"); //11
Console.WriteLine($"2nd watcher sees {w2.FooLimit}"); //21
Console.ReadKey();
}
}
}
You could use a Func int the constructor, something like:
private Limiter limiter;
private Func<Limiter, int> propertyAccesor;
public LimitWatcher(Limiter lim, string propName, Func<Limiter, int> propertyAccesor)
{
this.propertyAccesor = propertyAccesor;
}
public bool LimitExceeded()
{
int propertyValue = propertyAccesor(limiter);
return propertyValue > 20;
}
You could use dynamic expressions:
using System.Linq.Expressions;
public class LimitWatcher
{
public LimitWatcher(Limiter lim, string propName)
{
myLimiter = lim;
limitName = propName;
var parameter = Expression.Parameter(typeof(Limiter), "x");
var member = Expression.Property(parameter, propName);
var finalExpression = Expression.Lambda<Func<Limiter, int>>(member, parameter);
getter = finalExpression.Compile();
}
private Func<Limiter, int> getter;
private Limiter myLimiter { get; }
public string limitName { get; set; }
public int FooLimit { get { return getter(myLimiter); } }
}
Inspired by this article
I have following code:
public class A
{
public int MyProperty {get; set;}
}
public class B
{
A myInstance = new A();
myInstance.MyProperty = 10;
}
public class C
{
public void InvokeA()
{
//How to access MyPropery here?
BInstance = new B();
Console.WriteLine(B.myInstance.MyProperty.ToString());
}
}
I'm looking for a way to access MyProperty as written above. Inheritance is not an option since my class C is already inherited from some base class. A way without declaring any of the given classes as static would be nice!
Thanks,
Orz
Consider following classes:
public class A
{
public int MyProperty { get; set; }
}
public class B
{
public A GetAInstance()
{
A myInstance = new A();
myInstance.MyProperty = 10;
return myInstance;
}
}
public class C
{
private B BInstance;
public void InvokeA()
{
BInstance = new B();
Console.WriteLine(BInstance.GetAInstance());
}
}
and then you will create your C instance in Main:
static void Main(string[] args)
{
C cInstance = new C();
cInstance.InvokeA();
}
In order to accomplish your goal, you need to expose B.MyInstance as a property of the B class, just like you exposed A.MyProperty as a property of the A class.
Edit: Per the comments of others regarding use of the static keyword, here's what you might want your code to look like:
public class A
{
public int MyProperty { get; set; }
}
public static class B
{
static B()
{
MyInstance = new A();
MyInstance.MyProperty = 10;
}
public static A MyInstance { get; set; }
}
public class C
{
// not sure what your intention is here
public C()
{
System.Console.WriteLine(B.MyInstance.MyProperty.ToString()); // "10\n"
}
}
Yes. You can inherits classes from A to B something like this:
public class A
{
public int MyProperty {get; set;}
}
public class B : A
{
public B()
: A()
{
MyProperty = 1;
}
}
Now you can do:
(new B()).MyProperty
Or use Singleton approach to resolve:
public class B
{
private static _a;
public class A
{
public int MyProperty {get; set;}
}
public static A AA {
if (_a == null) {
_a = new A();
}
return _a;
}
}
This implmentation will return
B.A.MyProperty.ToString();
I have a multilingual database, which returns values based on a key and an enum Language. When I convert a DB object to a model, I want the model to contain the translated value based on the key and the current language.
The key comes from the DB object but how can I pass the current language to the the Mapper.Map() function?
Currently, I am using a [ThreadStatic] attribute to set the culture before calling Mapper.Map<>, and to retrieve it in the TypeConverter.
public enum Language
{
English, French, Italian, Maltese
}
public class MultilingualValue<T>
{
public Dictionary<Language, T> Value { get; set; }
public MultilingualValue()
{
this.Value = new Dictionary<Language, T>();
}
}
public class PersonData
{
public string FirstName { get; set; }
public MultilingualValue<string> City { get; set; }
}
public void MapPerson()
{
PersonData personData = new PersonData();
personData.FirstName = "John";
personData.City = new MultilingualValue<string>();
personData.City.Value[ Language.English] = "The Zurrieq";
personData.City.Value[Language.French] = "Le Zurrieque";
MultilingualValueData.CurrentLanguage = Language.English;
var personModel = Mapper.Map<PersonData, PersonModel>(personData);
}
public class MultilingualValueToBasicDataTypeConverter<T> : ITypeConverter<MultilingualValue<T>, T>
{
public T Convert(ResolutionContext context)
{
var currentLanguage = MultilingualValueData.CurrentLanguage; //THIS IS THE [ThreadStatic] VARIABLE
if (currentLanguage == null) throw new InvalidOperationException("Please make sure to fill in CurrentLanguage");
MultilingualValue<T> sourceMultilingualValue = (MultilingualValue < T > )context.SourceValue;
T destinationValue = default(T);
if (sourceMultilingualValue != null)
{
destinationValue = sourceMultilingualValue.Value[currentLanguage.Value];
}
return destinationValue;
}
}
public static class MultilingualValueData
{
[ThreadStatic]
public static Language? CurrentLanguage;
}
I left out the configurations as I think they're unneccessary for this example. If you need them, I'll post them as well.
While this works, I find this workaround quite ugly. Is there any way to pass data through the ResolutionContext?
Just use the Map overload that takes a Action<IMappingOperationOptions>. You can add configuration elements to the Items property that are then passed to your ITypeConverter
public class CustomConverter : ITypeConverter<string, string>
{
public string Convert(ResolutionContext context)
{
return "translated in " + context.Options.Items["language"];
}
}
internal class Program
{
private static void Main(string[] args)
{
AutoMapper.Mapper.CreateMap<string, string>().ConvertUsing<CustomConverter>();
var result = AutoMapper.Mapper.Map<string, string>("value" , opt => opt.Items["language"] = "english");
Console.Write(result); // prints "translated in english"
Console.ReadLine();
}
}
// stupid title, but I could not think anything smarter
I have a code (see below, sorry for long code but it's very-very simple):
namespace Option1
{
class AuxClass1
{
string _field1;
public string Field1
{
get
{
return _field1;
}
set
{
_field1 = value;
}
}
// another fields. maybe many fields maybe several properties
public void Method1()
{
// some action
}
public void Method2()
{
// some action 2
}
}
class MainClass
{
AuxClass1 _auxClass;
public AuxClass1 AuxClass
{
get
{
return _auxClass;
}
set
{
_auxClass = value;
}
}
public MainClass()
{
_auxClass = new AuxClass1();
}
}
}
namespace Option2
{
class AuxClass1
{
string _field1;
public string Field1
{
get
{
return _field1;
}
set
{
_field1 = value;
}
}
// another fields. maybe many fields maybe several properties
public void Method1()
{
// some action
}
public void Method2()
{
// some action 2
}
}
class MainClass
{
AuxClass1 _auxClass;
public string Field1
{
get
{
return _auxClass.Field1;
}
set
{
_auxClass.Field1 = value;
}
}
public void Method1()
{
_auxClass.Method1();
}
public void Method2()
{
_auxClass.Method2();
}
public MainClass()
{
_auxClass = new AuxClass1();
}
}
}
class Program
{
static void Main(string[] args)
{
// Option1
Option1.MainClass mainClass1 = new Option1.MainClass();
mainClass1.AuxClass.Field1 = "string1";
mainClass1.AuxClass.Method1();
mainClass1.AuxClass.Method2();
// Option2
Option2.MainClass mainClass2 = new Option2.MainClass();
mainClass2.Field1 = "string2";
mainClass2.Method1();
mainClass2.Method2();
Console.ReadKey();
}
}
What option (option1 or option2) do you prefer ? In which cases should I use option1 or option2 ? Is there any special name for option1 or option2 (composition, aggregation) ?
According to Law of Demeter, Option2. That way you can freely change the implementation of MainClass, You don't have to worry about calling code relying on details of AuxClass1, and indeed can remove it entirely if needed.
EDIT
interface IAuxClass1
{
string Field1 { get; set; }
void Method1();
void Method2();
}
class AuxClass1 : IAuxClass1
{
string _field1;
public string Field1
{
get
{
return _field1;
}
set
{
_field1 = value;
}
}
// another fields. maybe many fields maybe several properties
public void Method1()
{
// some action
}
public void Method2()
{
// some action 2
}
}
public class MyClass : ServiceContainer
{
public MyClass()
{
this.AddService(typeof(IAuxClass1), new AuxClass1());
}
public MyClass(IAuxClass1 auxClassInstance)
{
this.AddService(typeof(IAuxClass1), auxClassInstance);
}
public IAuxClass1 AuxClass
{
get
{
return (this.GetService(typeof(IAuxClass1)) as IAuxClass1);
}
}
}
Original
I tihnk MainClass should derive from AuxClass..
class MainClass : AuxClass1
{
}
I would start with implementing a nice feature of C# called "automatic properties". Instead of writing
private ThisType _myThing;
public ThisType MyThing
{
get { return _myThing; }
set { _myThing = value; }
}
you can write
public ThisType MyThing { get; set; }
and the compiler will generate the exact same IL. On top of this, you can add some options, for example making the setter private:
public ThisType MyThing { get; private set; }
In your case, I would go for option 3:
namespace Option3
{
public AuxClass
{
public string Field1 { get; set; }
public Method1() { ... }
public Method1() { ... }
}
public MainClass
{
public AuxClass Aux { get; private set; }
public MainClass(AuxClass aux)
{
this.Aux = aux;
}
}
}
class Program
{
static void Main(string[] args)
{
Option3.AuxClass = auxClass3 = new Option3.AuxClass();
Option3.MainClass mainClass3 = new Option3.MainClass(auxClass3);
mainClass3.Aux.Field1 = "string2";
mainClass3.Aux.Method1();
mainClass3.Aux.Method2();
}
}
This way, you lock the AuxClass reference once it's set (like in Option 2) while not locking up yourself for changes in the AuxClass interface (like in Option 1).
Decision of choosing design is based on different factors,
Shorter code => Option 1
Monitor activity of each functionality and every access => Option 2, however using linq and expressions, you can write a generalized code that can work with even option 1, but thats too complicated to discuss here.
C#4.0 brings optional parameters, which I've been waiting for for quite some time. However it seems that because only System types can be const, I cannot use any class/struct which I have created as an optional parameter.
Is there a some way which allows me to use a more complex type as an optional parameter. Or is this one of the realities that one must just live with?
The best I could come up with for reference types was:
using System;
public class Gizmo
{
public int Foo { set; get; }
public double Bar { set; get; }
public Gizmo(int f, double b)
{
Foo = f;
Bar = b;
}
}
class Demo
{
static void ShowGizmo(Gizmo g = null)
{
Gizmo gg = g ?? new Gizmo(12, 34.56);
Console.WriteLine("Gizmo: Foo = {0}; Bar = {1}", gg.Foo, gg.Bar);
}
public static void Main()
{
ShowGizmo();
ShowGizmo(new Gizmo(7, 8.90));
}
}
You can use the same idea for structs by making the parameter nullable:
public struct Whatsit
{
public int Foo { set; get; }
public double Bar { set; get; }
public Whatsit(int f, double b) : this()
{
Foo = f; Bar = b;
}
}
static void ShowWhatsit(Whatsit? s = null)
{
Whatsit ss = s ?? new Whatsit(1, 2.3);
Console.WriteLine("Whatsit: Foo = {0}; Bar = {1}",
ss.Foo, ss.Bar);
}
You can use any type as an optional parameter:
using System;
class Bar { }
class Program
{
static void Main()
{
foo();
}
static void foo(Bar bar = null) { }
}
Okay, I reread your question and I think I see what you mean - you want to be able to do something like this:
static void foo(Bar bar = new Bar()) { }
Unfortunately this is a not allowed since the value of the default parameter must be known at compile time so that the compiler can bake it into the assembly.