In C I can do
void foo() {
static int c = 0;
printf("%d,", c);
c ++;
}
foo();
foo();
foo();
foo();
it should print 0,1,2,3
Is there an equivalent in C#?
While some have suggested as static member variable, this is not the same due to visibility. As an alternative to the answer by aquinas, if closures are accepted, then this can be done:
(Note that Foo is a a property and not a method and that c is "per instance".)
class F {
public readonly Action Foo;
public F () {
int c = 0; // closured
Foo = () => {
Console.WriteLine(c);
c++;
};
}
}
var f = new F();
f.Foo(); // 0
f.Foo(); // 1
However, C# has no direct equivalent to a static variable in C.
Happy coding.
Something like:
class C
{
private static int c = 0;
public void foo()
{
Console.WriteLine(c);
c++;
}
}
No there is no way to achieve the same behaviour as the static c function variable ...
There are no globals in C#, however, you can create a static field within your class.
public class Foo{
private static int c = 0;
void Bar(){
Console.WriteLine(c++);
}
}
You can't do it at a method level. The closest you can do at a method level is something like this, and this isn't really that close. In particular, it only works if you have a reference to the enumerator. If someone else calls this method, they won't see your changes.
class Program {
static IEnumerable<int> Foo() {
int c = 0;
while (true) {
c++;
yield return c;
}
}
static void Main(string[] args) {
var x = Foo().GetEnumerator();
Console.WriteLine(x.Current); //0
x.MoveNext();
Console.WriteLine(x.Current); //1
x.MoveNext();
Console.WriteLine(x.Current); //2
Console.ReadLine();
}
}
What interesting is that VB.NET does support static local variables: http://weblogs.asp.net/psteele/pages/7717.aspx. As this page notes, .NET itself doesn't support this, but the VB.NET compiler fakes it by adding a static class level variable.
Related
This is the Question I am trying to solve in C Sharp.
I am getting an error:
Error Expected ; or = (cannot specify constructor arguments in declaration)
Can anyone help me to solve this or guide me to solve this?
namespace program
{
public class Integer
{
private int intvar;
public Integer()
{
intvar = 0;
}
public Integer(int x)
{
intvar = x;
}
public void display()
{
Console.Write(intvar);
Console.Write("\n");
}
public void add(Integer x, Integer y)
{
intvar = x.intvar + y.intvar;
}
}
class Program
{
static void Main(string[] args)
{
Integer a(5),b(45);
Integer c;
c.add(a,b);
c.display();
Console.ReadLine();
}
}
}
You cannot create objects like that in C#. Im assuming you come from C++ where this syntax is possible.
In C# you have to create objects using new:
Integer foo = new Integer(45);
To create a new instance of a type, you have to invoke one of the constructors of that type using the new operator. For example:
class Program
{
static void Main(string[] args)
{
var a = new Integer(5);
var b = new Integer(45);
var c = new Integer(); //result instance
c.add(a, b);
c.display();
Console.ReadLine();
}
}
I am creating a C# library with some reusable code and was trying to create a method inside a method. I have a method like this:
public static void Method1()
{
// Code
}
What I would like to do is this:
public static void Method1()
{
public static void Method2()
{
}
public static void Method3()
{
}
}
Then I could choose either Method1.Method2 or Method1.Method3. Obviously the compiler isn't happy about this, any help is much appreciated. Thanks.
If by nested method, you mean a method that is only callable within that method (like in Delphi) you could use delegates.
public static void Method1()
{
var method2 = new Action(() => { /* action body */ } );
var method3 = new Action(() => { /* action body */ } );
//call them like normal methods
method2();
method3();
//if you want an argument
var actionWithArgument = new Action<int>(i => { Console.WriteLine(i); });
actionWithArgument(5);
//if you want to return something
var function = new Func<int, int>(i => { return i++; });
int test = function(6);
}
Yes, when C# 7.0 is released, Local Functions will allow you to do that. You will be able to have a method, inside a method as:
public int GetName(int userId)
{
int GetFamilyName(int id)
{
return User.FamilyName;
}
string firstName = User.FirstName;
var fullName = firstName + GetFamilyName(userId);
return fullName;
}
Note that public (and similar modifiers) are not supported C# programming guide:
Because all local functions are private, including an access modifier, such as the private keyword, generates compiler error CS0106, "
This answer was written before C# 7 came out. With C# 7 you can write local methods.
No, you can't do that. You could create a nested class:
public class ContainingClass
{
public static class NestedClass
{
public static void Method2()
{
}
public static void Method3()
{
}
}
}
You'd then call:
ContainingClass.NestedClass.Method2();
or
ContainingClass.NestedClass.Method3();
I wouldn't recommend this though. Usually it's a bad idea to have public nested types.
Can you tell us more about what you're trying to achieve? There may well be a better approach.
You can define delegates within your method with complete code and call them if you want.
public class MyMethods
{
public void Method1()
{
// defining your methods
Action method1 = new Action( () =>
{
Console.WriteLine("I am method 1");
Thread.Sleep(100);
var b = 3.14;
Console.WriteLine(b);
}
);
Action<int> method2 = new Action<int>( a =>
{
Console.WriteLine("I am method 2");
Console.WriteLine(a);
}
);
Func<int, bool> method3 = new Func<int, bool>( a =>
{
Console.WriteLine("I am a function");
return a > 10;
}
);
// calling your methods
method1.Invoke();
method2.Invoke(10);
method3.Invoke(5);
}
}
There is always an alternative of using a nested class within a class that will not be visible from outside and calling its methods, like:
public class SuperClass
{
internal static class HelperClass
{
internal static void Method2() {}
}
public void Method1 ()
{
HelperClass.Method2();
}
}
As of C# 7.0 you can do that:
public static void SlimShady()
{
void Hi([CallerMemberName] string name = null)
{
Console.WriteLine($"Hi! My name is {name}");
}
Hi();
}
This is called local functions, that is just what you were looking for.
I took the example from here, but further informatin can be found here and here.
Why you don't use classes?
public static class Helper
{
public static string MethodA()
{
return "A";
}
public static string MethodA()
{
return "A";
}
}
Now you can acces MethodA via
Helper.MethodA();
Older thread, but C# does have the concept of nested functions
Func<int> getCalcFunction(int total, bool useAddition)
{
int overallValue = 0;
if (useAddition)
{
Func<int> incrementer = new Func<int>(() =>
{
overallValue += total;
return overallValue;
});
return incrementer;
}
else
{
Func<int> decrementer = new Func<int>(() =>
{
overallValue -= total;
return overallValue;
});
return decrementer;
}
}
private void CalcTotals()
{
Func<int> decrem = getCalcFunction(30, false);
int a = decrem(); //result = -30
a = decrem(); //result = -60
Func<int> increm = getCalcFunction(30, true);
int b = increm(); //result = 30
b = increm(); //result = 60
}
Your nearly there
public static void Method1()
should be
public static class Method1{}
Don't you want to use nested class instead?
That's said, you seem to not respect the Single Responsibility Principle because you want a single method do more than one thing at a time.
Why don't you just Run a method within another
public void M1()
{
DO STUFF
}
public void M1()
{
DO STUFF
M1();
}
First of all, take a look at my below code:
class A
{
public static int Flag()
{
return 0;// set initial value=0
}
B b= new B();
public void afunc()
{
b.bfunc();
}
}
And class B recieves and sends static variable:
class B
{
A a= new A();
int flag= a.Flag();
public void bfunc()
{
if(flag==0)
{
flag=1;//???? is this wrong???
//do some thing
}
}
}
Class A send to B a static variable with initial value=0; then class A call bfunc from class B. In bfunc() I set flag=1. I'm a new to C#. Can you share me how class A recieves back flag=1 sended by class B. I mean which syntax?
a few things are wrong here
Flag is a method on A, so you cannot change its "value"
Flag is static therefore it does not have an instance which is what I think you want
I suspect you want Flag to be a property of A
public int Flag{get;set;}
You are making new instances of A and B, which may be correct for you but be weary this means you are not referencing existing instances
You have two options
A
this.Flag = b.bFunc();
public int bFunc()
.... return 1;
B
public void bFunc()
... a.Flag = 1;
If you really want static variable then
public static int Flag = 0;
A.Flag = x
Were is no static variable here, you only have a static function int Flag(). To get value of a flag in class A, you must return this value from function bfunc() like this:
public int bfunc()
{
if(flag==0)
{
flag=1;
return flag;
}
}
I don't know if I understood you properly because there are many things wrong with your code. Flag should be a property instead of a method so you can store your value. The way you used it was just tossing out a zero.
First, your two classes. Keep in mind that usually properties should be used as accesssors to private fields, but let's do it the simplest way.
class A
{
public static int Flag = 0;
}
class B
{
public void bfunc()
{
if (A.Flag == 0)
{
A.Flag = 1;
}
}
}
Then use them as follows to change Flag's value.
B bObject = new B();
bObject.bfunc();
// A.Flag is now 1.
Note that bfunc() will change Flag's value to 1 only if it was 0 before.
I'm trying to recreate this in C#.
The problem i get is if i use constructors i MUST use new MyInt which i DO NOT WANT (to verbose). The way around it is to use the implicit/explicit operators. However they MUST be public... How the heck do i implement this in feature in C#?
The short question is i'd like to pass byte/short into a function but not int. Passing int should get me a compile error. I know i can easily get runtime with a public implicit int operator. The code below shows that int is automatically converted to char
Running sample shows true
using System;
class Program
{
public static void Write(MyInt v)
{
Console.WriteLine("{0}", v.v is byte);
}
static void Main(string[] args)
{
Write(2);
}
}
public struct MyInt
{
public object v;
public MyInt(byte vv) { v = vv; }
public MyInt(short vv) { v = vv; }
public MyInt(byte[] vv) { v = vv; }
public static implicit operator MyInt(byte vv) { return new MyInt { v = vv }; }
//public static extern implicit operator MyInt(int vv);
}
Heres more code which is useless. It implements MyInt2/MyInt which isn't required in the C++ solution
Just declare that your function takes short. Byte would be implicitly converted to short, but there is no implicit conversion from int to short, so int just won't pass
public class Class1
{
public static void Aaa(short a)
{
}
public void Bbb()
{
int i = 5;
byte b = 1;
short c = 1;
Class1.Aaa(i); // Gives error
Class1.Aaa(b); // Ok
Class1.Aaa(c); // ok
}
}
I am creating a C# library with some reusable code and was trying to create a method inside a method. I have a method like this:
public static void Method1()
{
// Code
}
What I would like to do is this:
public static void Method1()
{
public static void Method2()
{
}
public static void Method3()
{
}
}
Then I could choose either Method1.Method2 or Method1.Method3. Obviously the compiler isn't happy about this, any help is much appreciated. Thanks.
If by nested method, you mean a method that is only callable within that method (like in Delphi) you could use delegates.
public static void Method1()
{
var method2 = new Action(() => { /* action body */ } );
var method3 = new Action(() => { /* action body */ } );
//call them like normal methods
method2();
method3();
//if you want an argument
var actionWithArgument = new Action<int>(i => { Console.WriteLine(i); });
actionWithArgument(5);
//if you want to return something
var function = new Func<int, int>(i => { return i++; });
int test = function(6);
}
Yes, when C# 7.0 is released, Local Functions will allow you to do that. You will be able to have a method, inside a method as:
public int GetName(int userId)
{
int GetFamilyName(int id)
{
return User.FamilyName;
}
string firstName = User.FirstName;
var fullName = firstName + GetFamilyName(userId);
return fullName;
}
Note that public (and similar modifiers) are not supported C# programming guide:
Because all local functions are private, including an access modifier, such as the private keyword, generates compiler error CS0106, "
This answer was written before C# 7 came out. With C# 7 you can write local methods.
No, you can't do that. You could create a nested class:
public class ContainingClass
{
public static class NestedClass
{
public static void Method2()
{
}
public static void Method3()
{
}
}
}
You'd then call:
ContainingClass.NestedClass.Method2();
or
ContainingClass.NestedClass.Method3();
I wouldn't recommend this though. Usually it's a bad idea to have public nested types.
Can you tell us more about what you're trying to achieve? There may well be a better approach.
You can define delegates within your method with complete code and call them if you want.
public class MyMethods
{
public void Method1()
{
// defining your methods
Action method1 = new Action( () =>
{
Console.WriteLine("I am method 1");
Thread.Sleep(100);
var b = 3.14;
Console.WriteLine(b);
}
);
Action<int> method2 = new Action<int>( a =>
{
Console.WriteLine("I am method 2");
Console.WriteLine(a);
}
);
Func<int, bool> method3 = new Func<int, bool>( a =>
{
Console.WriteLine("I am a function");
return a > 10;
}
);
// calling your methods
method1.Invoke();
method2.Invoke(10);
method3.Invoke(5);
}
}
There is always an alternative of using a nested class within a class that will not be visible from outside and calling its methods, like:
public class SuperClass
{
internal static class HelperClass
{
internal static void Method2() {}
}
public void Method1 ()
{
HelperClass.Method2();
}
}
As of C# 7.0 you can do that:
public static void SlimShady()
{
void Hi([CallerMemberName] string name = null)
{
Console.WriteLine($"Hi! My name is {name}");
}
Hi();
}
This is called local functions, that is just what you were looking for.
I took the example from here, but further informatin can be found here and here.
Why you don't use classes?
public static class Helper
{
public static string MethodA()
{
return "A";
}
public static string MethodA()
{
return "A";
}
}
Now you can acces MethodA via
Helper.MethodA();
Older thread, but C# does have the concept of nested functions
Func<int> getCalcFunction(int total, bool useAddition)
{
int overallValue = 0;
if (useAddition)
{
Func<int> incrementer = new Func<int>(() =>
{
overallValue += total;
return overallValue;
});
return incrementer;
}
else
{
Func<int> decrementer = new Func<int>(() =>
{
overallValue -= total;
return overallValue;
});
return decrementer;
}
}
private void CalcTotals()
{
Func<int> decrem = getCalcFunction(30, false);
int a = decrem(); //result = -30
a = decrem(); //result = -60
Func<int> increm = getCalcFunction(30, true);
int b = increm(); //result = 30
b = increm(); //result = 60
}
Your nearly there
public static void Method1()
should be
public static class Method1{}
Don't you want to use nested class instead?
That's said, you seem to not respect the Single Responsibility Principle because you want a single method do more than one thing at a time.
Why don't you just Run a method within another
public void M1()
{
DO STUFF
}
public void M1()
{
DO STUFF
M1();
}