I have a situation in which I have a class called myClasses and two sub classes called subOne and subTwo.
class myClasses
{
class subOne
{
public const SOfieldOne = "blahblah";
public const SOfieldTwo = "blahblahblah";
}
class subTwo
{
public const STfieldOne = "blahblah";
}
}
I want to be able to set a variable to either class subOne or subTwo based on an argument passed to one of my methods. I then want to be able to access the members within subOne or subTwo using this general variable.
For example if the argument is "useSubOne" I want to set a variable subToUse as so...
subToUse = myClasses.subOne;
I should then be able to access SOfieldOne by typing the following...
subToUse.SOfieldOne
How would I go about doing this?
Polymorphism does not apply to constants. Here's how your code could look like instead:
private class myClasses
{
private class subOne
{
public virtual string SOfieldOne
{
get { return "blahblah"; }
}
}
private class subTwo : subOne
{
public override string SOfieldOne
{
get { return "something else"; }
}
}
}
Now you can create a new variable like this:
subOne someVariable = new subTwo();
Console.WriteLine(someVariable.SOfieldOne); // Prints "something else"
Related
I have code like below. Interface with default implementation. And the user who uses this interface. But for some reason in the switch case my code uses the default implementation of the interface for the "Name' instead of the class implementation. What should i change to see "Ben" in console?
namespace ConsoleApp1
{
public interface IUser
{
// Interface with default implementation
public string Name { get => "Tom"; }
}
// User using this interface
public class BenUser : IUser
{
public string Name = "Ben";
}
public static class MainClass
{
public static void ShowName(IUser user)
{
switch (user.Name)
{
case "Ben": // I expected the code to run here
Console.WriteLine("Ben");
break;
case "Tom": // But the code goes here
Console.WriteLine("Tom");
break;
}
}
static void Main()
{
// Create a user with Name "Ben"
var ben = new BenUser();
ShowName(ben); // In console i see "Tom" for some reason
}
}
}
I can't figure out why the code is behaving like this.
As mentioned in comments, you need to implement the interface using the same shape in your class - as a property with a get.
public interface IUser
{
// Interface with default implementation
public string Name { get => "Tom"; }
}
// User using this interface
public class BenUser : IUser
{
public string Name { get => "Ben"; }
}
public static class MainClass
{
public static void ShowName(IUser user)
{
switch (user.Name)
{
case "Ben": // I expected the code to run here
System.Console.WriteLine("Ben");
break;
case "Tom": // But the code goes here
System.Console.WriteLine("Tom");
break;
}
}
static void Main()
{
// Create a user with Name "Ben"
var ben = new BenUser();
ShowName(ben); // In console i see "Tom" for some reason
}
}
This is my edit to show some more standard practices, please read through the comments and see if it makes anything more clear. The standard practice for creating members is to use accesslevel Type VariableName { get; set; }
namespace ConsoleApp1
{
public interface IUser
{
//denotes that this is set by construction, cannot be set afterwards
public string Name { get; }
}
// User using this interface
public class BenUser : IUser
{
// Standard 'getter' only member with a compiled return value
public string Name
{
get
{
return "Ben";
}
}
}
public class User : IUser
{
// private settable string to use with construction
private string _name;
// constructor
public User(string userName)
{
// sets the private variable to desired value
_name = userName;
}
// public 'getter' that returns the set value
public string Name
{
get
{
return _name;
}
}
}
public static class MainClass
{
public static void ShowName(IUser user)
{
Console.WriteLine(user.Name);
}
static void Main()
{
// Create a user with static Name "Ben"
var ben = new BenUser();
ShowName(ben);
// Create a user with variable Name set as "Carl"
var carl = new User("Carl");
ShowName(carl);
}
}
}
The Name in IUser is a property while Name in BenUser is a field. With your code when we do user.Name it calls the get method defined in IUser instead of getting value of Name field from BenUser. Here is a sample implementation for fixing your bug.
public class BenUser : IUser
{
public string Name { get => "Ben"; }
}
I would recommend to not do it the way you are doing because Name identifier has become embiguos
I have a class library project, I want to create a variable and assign a value to it through MethodA() whose value can be access through MethodB().
Just like we have a session in ASP.NET.
I cannot pass as a parameter to MethodB() because MethodB() is being used in many places and if I change it, all the other methods will get affected.
Public Void MethodA()
{
string value ="Hello";
}
public Void MethodB()
{
-- I want to read the value which is set in MethodA()
}
I need to dispose the value as well after reading it in MethodB().
Both of these methods are in different classes inside the same project.
First try to create a property with a private setter:
public class A
{
public string Value { get { return MethodA(); } }
public string MethodA()
{
return "Hello";
}
public void MethodB()
{
var value = Value;
}
}
If you have two classes:
public class A
{
public string FooMethod()
{
return string.Empty;
}
}
public class B
{
public string BarMethod()
{
var result = new A().FooMethod();
return result;
}
}
You can get idea to handle your exception
public class test
{
public static int value = 0; //Global variable
public void MethodA()
{
//you can assign here as well
value++;
}
}
public class HomeController : Controller
{
test t = new test();
public IActionResult Index()
{
t.MethodA();
int d = test.value;
//you can assign here as well
test.value = 100;
int dd = test.value;
return View();
}
}
What I have is:
public static class IDs {
public static string someID { get; set; }
static IDs() {
log.info(someID);
// use someID here
}
}
public class otherClass {
public void otherMethod(string sym) {
IDs.someID = sym;
}
}
and then using an instance of otherClass like this:
otherClassInstance.otherMethod("someStringSymbol");
I dont have any build errors, but log.info(someID); is printing null.
I was expecting it to be someStringSymbol.
This is because the static constructor is called automatically before the first instance is created or any static members are referenced..
This means that when an instance of otherClass invokes IDs.someID = sym; the first operation that gets executed is the static constructor, i.e. the code inside static IDs().
At this point the static variable has not yet been initialized, and you are basically executing log.info(null);.
After the static constructor completes, the variable is initialized, so you should be able to see its value inside otherMethod, after the first reference of IDs.
Given the OP's requirement:
I want to use the value passed in someID in a switch statement
The solution could be to simply execute a static method whenever a new value is set, with the help of explicit getters and setters:
public static class IDs
{
private static string _someID; // backing field
public static string SomeID
{
get { return _someID; }
set
{
_someID = value;
DoSomethingWithSomeID();
}
}
private static DoSomethingWithSomeID()
{
// Use SomeID here.
switch (IDs.SomeID)
{
...
}
}
}
public class OtherClass
{
public void OtherMethod(string sym)
{
// This will set a new value to the property
// and invoke DoSomethingWithSomeID.
IDs.SomeID = sym;
}
}
DoSomethingWithSomeID will be invoked every time someone sets a new value to SomeID.
I dont think what you are trying to do is suited to static classes. I would try the following
public class IDs{
public string someID{ get; set; }
public IDs(string someId){
this.someID = someId;
log.info(this.someID);
//use someID here
}
}
pulic class otherClass{
public otherMethod(string sym){
IDs id = new IDs(sym);
}
}
public class anotherClass{
//access instance of otherClass in wrp and call otherMethod()
wrp.otherMethod("someStringSymbol")
}
Is there a way know which class has called a function in another class.
Eg:
public class A
{
public static string Aa = "test";
public void test()
{
B.testB();
}
}
public class B
{
public static void testB()
{
string Bb = A.Aa;
}
}
In the above example, i know the class A function has called the function in class B. But if there are many classes which will call the function in class B and all of those classes will have variable Aa in common, so how can i read its value and assign it to Bb. So in simple
string Bb = CalledClassName.Aa;
You could use the CallerMemberNameAttribute that was added with .NET 4.5. This will only get you the member name though:
public void SomeMethod ()
{
OtherMethod();
}
public void OtherMethod ([CallerMemberName] string memberName = null)
{
Console.WriteLine(memberName);
}
The attribute will fill the optional parameter at compile time, so it will actually call OtherMethod("SomeMethod").
You could also use a combination of accessing the stack trace and using reflection to read the Aa property of the type of the calling method. Note that this accesses debugging information, and is very vulnerable to changes in your code. It also has a bad performance, so you should avoid it. But just to show you how to use it:
public static void testB()
{
StackTrace stackTrace = new StackTrace();
Type callingType = stackTrace.GetFrame(1).GetMethod().DeclaringType;
FieldInfo field = callingType.GetField("Aa", BindingFlags.Public | BindingFlags.Static);
string Bb = (string) field.GetValue(null);
Console.WriteLine(Bb);
}
Use an interface, pass that in:
public interface AaInterface {
public string GetAa();
}
public class A : AaInterface
{
public static string Aa = "test";
public GetAa() { return Aa; }
public void test()
{
B.testB(this);
}
}
public class B
{
public static void testB(AaInterface pAa)
{
string Bb = pAa.GetAa();
}
}
I guess you are looking for something different than you are asking.
You should pass the instance of A to your method. All calling methods should pass the instance based on an interface. In that interface you put the properties and methods you want to share. In that way you can call the 'same' method for every passed instance.
public interface ISomeInterface
{
string Aa {get;}
}
public class A : ISomeInterface
{
public string Aa {get { return "a"; } }
}
Then you can pass it to this method:
public static void testB(ISomeInterface something)
{
string Bb = something.Aa;
}
Note that in this case, Aa is not allowed to be static. You could wrap that static in an instance property though.
If i understood your question correctly then you can pass a reference to a class instance in method as parameter then use 'is' operator to check its type:
public class A
{
public static string Aa = "test";
public void test(object calledClass)
{
if(calledClass is B) Aa = calledClass.Bb;
}
}
When you call this static method from class B just put :
A.Test(this)
P.S.
This is just an example of logic that you can use to achieve what you want
I geuss you can do something like this:
public class A {
public void test() {
B.testB(this);
}
}
public class B {
public static void testB(object sender) {
String className = sender.GetType().Name;
}
}
//To call
A a = new A();
a.test();
I want to access a string from one class to another. I have used the property method as follows -
Myclass.cs
public class MyClass
{
private string _user;
public string user
{ get { return this._user; } set { this._user = value; } }
}
consumption.aspx.cs
I am assigning the value to user in a function
MyClass m = new MyClass();
m.user = "abc"
Now when I try to use this value in my another function which is called after this value is assigned
RawDal.cs
MyClass m = new MyClass();
string x = m.user;
I get empty value... How to do it?
As already mentioned in the comments you are creating two separate instances of MyClass which results simplified in something like:
int a;
a = 3;
int b;
Console.WriteLine("a: " + b); //<-- here it should be obvious why b is not 3
You can work around this in 3 ways:
1) Use the same instance of MyClass for the second call, but in this case you need to be in the same scope or pass the instance on to the new scope.
2) Make the property/member static:
public class MyClass
{
public static string User { get; set; } //the "static" is the important keyword, I just used the alternative property declaration to keep it shorter
}
Then you can access the same User value everywhere via MyClass.User.
3) Use a singleton:
public class MyClass
{
private static MyClass instance = null;
public static MyClass Instance
{
get
{
if(instance == null)
instance = new MyClass();
return instance;
}
}
public string User { get; set; }
}
Then you can access it via MyClass.Instance.User.
There are possibly some more solutions, but these are the common ones.
You are not using the same instance. Try
public class MyClass
{
private string _user;
public string user
{ get { return this._user; } set { this._user = value; } }
}
public string YourFunction()
{
MyClass m = new MyClass();
m.user = "abc"
return m.user;
}
If all you want to return is a string try something like
string x = YourFunction();