public int userID;
//global variable
public Index()
{
userID = 10;
return userID;
}
public TaskCompleted()
{
Console.WriteLine(Index())
}
i want the userID to be accessed in each and every method and can we updated anywhere
Your Index method has two problems.
Syntax problem: Every method must have a return type. Either a real type like int or the void keyword.
public int Index()
Semantic problem. At every call it sets userID and returns it. Why store the value in this variable? It will be replaced by a new value at the next call and could just be a local variable (i.e., a variable inside the method) or be dismissed completely. But maybe your example was simply not complete.
Let's try different approaches:
Passing value through a class field (your "global" variable).
private int _userId;
public void SetUserId() // `void` means that the method is not returning a value.
{
_userId = 10;
}
public void PrintUserId()
{
Console.WriteLine(_userId);
}
This requires you to call SetUserId(); before calling PrintUserId();
Let the method return the value.
public int GetUserId() // `int` means that the method is returning an `int` value
{
return 10;
}
public void PrintUserId()
{
Console.WriteLine(GetUserId());
}
Combine the two previous approaches
private int _userId;
public void SetUserId()
{
_userId = 10;
}
public int GetUserId()
{
return _userId;
}
public void PrintUserId()
{
Console.WriteLine(GetUserId());
}
C# has a concept called "property". A property is a set of "Get" and "Set" methods, just as in the previous example, but with as special syntax.
private int _userId;
public UserId
{
get { return _userId; }
set { _userId = value; }
}
public void PrintUserId()
{
Console.WriteLine(UserId);
}
A property having no additional logic besides assigning and returning a value can also be implemented as an auto-property.
public int UserId { get; set; } // A hidden field is automatically created.
The caller would have to do something like this:
var obj = new MyClass();
obj.UserId = 10;
obj.PrintUserId();
You can use a static property of a static class:
public static class Globals
{
public static int UserID {get; set;}
}
Usage: var userId = Globals.UserID;
I am new to C# I am trying to pass a value to a method but receiving 0.Creating an instance to the main method of calc and calling the calc methods in main.
public void test()
{
var calc = new Calc();
calc.Add(1);
var actual = calc.Value;
}
public class Calc
{
public int Value{
get; set;
}
public void Add(int value)
{
int result = value + value;
}
I am trying to set the current value, how could I do that?
I'd suggest refactoring it a bit so the variable names are more clear. Your initial problem is that you weren't doing anything with the result, when really you wanted to set it to your property.
public class Calc
{
public int CurrentValue { get; set; }
public void Add(int number)
{
this.CurrentValue = this.CurrentValue + number;
}
}
The result of your Add method is not stored anywhere, i.e. the after the method is complete all the memory allocated while it was executed, is released. If you wish to save the result of your method you should either return it (which will require changing your method's prototype) or save it in a member of you class and access it with an appropriate property or getter-method.
Your class should be something like this:
public class Calc
{
private int result;
public int Value
{
get { return result; }
set { result = value; }
}
public void Add(int value)
{
result = value + value;
}
}
Please note that currently the Add methods just saves the result of two times of the value of the sent parameter value into the class member result
I think you want something more like this:
public class Calc
{
public int Value{
get; private set;
}
public void Add(int value)
{
this.Value += value;
}
}
Note I changed your Value to have a private setter, so that only the Calc class has access to change its value, whereas other objects are still able to retrieve its value.
Notice the change in the Add function, we're adding the value passed into the function onto your Value property. In your case you were just creating a new variable result in each call of the Add method, and then doing nothing with it.
You can see it in action here
Just got to know about C# snippet. But i am unable to use them in my code.
Help me out please, I am messed up with get set and how they work.
Here is my test class named "myclass"
namespace WindowsFormsApplication1
{
class myclass
{
public string getmessage(string givenName)
{
return "HB "+givenName;
}
private string bmessage;
public string MyProperty
{
get { return bmessage; }
set { bmessage = value; }
}
}
}
In button code from my form. I am unable to use these get set.
It ll be great if someone clears that how can i use these get set.
Moreover what is "MyProperty" here? I know it is not a method. What is its purpose? Thanks
Snippets itself are not executable statements. But are short-cuts that help you in writing executable statements.
For e.g.
If we write prop and press enter, it will give you a auto-generated property. You just have to change Datatype and Property Name.
Similarly propfull will give a property with get and set parts.
In your case MyProperty is the Property Name and string is the DataType. bmessage is the backing field for your property.
The properties of a class are set and retrieved by using set/get methods. Basically these are also methods.
namespace BusinessObjects
{
public class class_BusinessObjects
{
int StusentId;
string StudentName;
public class_BusinessObjects ()
{
StusentId = 0;
StudentName = string.Empty;
}
public int StusentId
{
get
{
return Id;
}
set
{
Id = value;
}
}
public string StudentName
{
get
{
return Name;
}
set
{
Name = value;
}
}
}
}
using BusinessObjects;
namespace MyModel
{
public class A
{
public class_BusinessObjects Dispaly(int id, string name)
{
class_BusinessObjects obj = new class_BusinessObjects();
obj.StusentId = id;
obj.StudentName = name;
return obj;
}
}
}
Is it possible to set or override the default state for a structure?
As an example I have an
enum something{a,b,c,d,e};
and a structure that links 2 values for that enum
struct SomethingData
{
something type;
int Value;
double Multipler;
SomethingData(something enumVal, int intVal, double DblVal) {...}
}
But can I specify that the default state is
SomethingData(something.c,0,1);
Struct constructors are similar to
class constructors, except for the
following differences:
Structs cannot contain explicit
parameterless constructors. Struct
members are automatically initialized
to their default values. A struct
cannot have an initializer in the
form: base (argument-list).
http://msdn.microsoft.com/en-us/library/aa288208(v=vs.71).aspx
So, short answer, no you can't override the default constructor (every struct has a parameterless constructor and you can't hide it or override it)...
You can't. Structs always have a default constructor that sets every member to its default value (null for reference types, 0 for numeric types, false for bools, etc.) This behavior cannot be changed.
You can't override the default (parameterless) constructor for a struct. You can only add new constructors, which take parameters.
http://csharp.2000things.com/2010/10/03/108-defining-a-constructor-for-a-struct/
Creating a class object will cause all of the instance fields to come into existence before anything--even the class constructor--can access it, and allocating an array will cause all of its elements to exist before anything can access the array. Both of these actions will cause all of the memory allocated to those fields or elements to be zeroed out without regard for the data types to be stored therein.
When a class-type storage location comes into existence, it will initially hold a null reference. When a structure-type storage location comes into existence, all of its fields (and any fields of structures within it) will do so simultaneously. Unlike class object instances which can only come into existence by using a constructor, structure-type storage locations are brought into existence without using any of the structure's own code. Consequently, the structure's definition will have no say in what should happen when "instances" [i.e. struct-type storage locations] come into existence.
A struct is, fundamentally, a collection of fields bound together with duct tape. If a struct is supposed to behave like something else, it should typically make its fields private and pretend to be immutable [even though struct assignment actually mutates the destination struct by overwriting all its fields with the corresponding values from the source, and the struct definition gets no say in the matter]. If, however, a struct is supposed to encapsulate a fixed set of related but independent values (e.g. the coordinates of a point), which may independently accommodate any combination of values which are legal for their respective types, a struct should simply expose its fields publicly. Some people may whine about "mutable structs are evil", but the evils only apply when invoking self-mutating methods on a struct. Structs which expose their state as fields behave like collections of variables stuck together with duct tape. If what one needs is a collection of variables stuck together with duct tape, trying to make a struct pretend to be immutable will simply make it harder to program with.
There is a workaround to make this happen by using custom Property getters. Observe:
public struct Foostruct
{
private int? _x;
private int? _y;
public int X
{
get { return _x ?? 20; } // replace 20 with desired default value
set { _x = value; }
}
public int Y
{
get { return _y ?? 10; } // replace 10 with desired default value
set { _y = value; }
}
}
This will only work for value types (which can be wrapped with nullable) but you could potentially do something similar for reference types by wrapping them in a generic class like below:
public class Wrapper<TValue>
{
public TValue Value { get; set; }
}
public struct Foostruct
{
private Wrapper<Tick> _tick;
public Tick Tick
{
get { return _tick == null ? new Tick(20) : _tick.Value; }
set { _tick = new Wrapper<Tick> { Value = value }; }
}
}
Somewhat related: I've often wanted to use the new object initializer syntax with an immutable value type. However, given the nature of a typical immutable value type implementation, there is no way to utilize that syntax, since the properties are read-only.
I've come up with this approach; In my opinion this still satisfies the immutability of the value type, but allows the code that is responsible for instantiating the value type greater control over the initialization of the internal data.
struct ImmutableValueType
{
private int _ID;
private string _Name;
public int ID
{
get { return _ID; }
}
public string Name
{
get { return _Name; }
}
// Infuser struct defined within the ImmutableValueType struct so that it has access to private fields
public struct Infuser
{
private ImmutableValueType _Item;
// write-only properties provide the complement to the read-only properties of the immutable value type
public int ID
{
set { _Item._ID = value; }
}
public string Name
{
set { _Item._Name = value; }
}
public ImmutableValueType Produce()
{
return this._Item;
}
public void Reset(ImmutableValueType item)
{
this._Item = item;
}
public void Reset()
{
this._Item = new ImmutableValueType();
}
public static implicit operator ImmutableValueType(Infuser infuser)
{
return infuser.Produce();
}
}
}
class Program
{
static void Main(string[] args)
{
// use of object initializer syntax made possible by the Infuser type
var item = new ImmutableValueType.Infuser
{
ID = 123,
Name = "ABC",
}.Produce();
Console.WriteLine("ID={0}, Name={1}", item.ID, item.Name);
}
}
Each time you get/set property you need to set default value call InitDefaultValues() method
private string _numberDecimalSeparator;
public string NumberDecimalSeparator
{
get
{
InitDefaultValues();
return _numberDecimalSeparator;
}
set
{
InitDefaultValues();
_numberDecimalSeparator = value;
}
}
...
private void InitDefaultValues()
{
if (!_inited)
{
_inited = false;
var ci = CultureInfo.CurrentCulture;
_numberDecimalSeparator = ci.With(x => x.NumberFormat).Return(x => x.NumberDecimalSeparator, ".");
...
}
}
Kinda dumb, but works
public readonly static float default_value = 1;
public struct YourStruct{
public float yourValue{
get {
return _yourValue + default_value;
}
set {
_yourValue= value - default_value;
}
}
public float _yourValue;
}
My solution. It works as well.
public struct DisplayOptions
{
public bool isUpon;
public bool screenFade;
public static DisplayOptions Build()
{
// Return default value
return new DisplayOptions(true, true);
}
DisplayOptions(bool isUpon, bool screenFade)
{
this.isUpon = isUpon;
this.screenFade = screenFade;
}
public DisplayOptions SetUpon(bool upon)
{
this.isUpon = upon;
return this;
}
public DisplayOptions SetScreenFade(bool screenFade)
{
this.screenFade = screenFade;
return this;
}
}
Use default value
// Use default
UIMaster.Instance.StartScreen("Screen 2", DisplayOptions.Build());
// Use custome
UIMaster.Instance.StartScreen("Screen 2", DisplayOptions.Build().SetScreenFade(false));
UIMaster.Instance.StartScreen("Screen 2", DisplayOptions.Build().SetUpon(false));
this should work
public struct MyStruct
{
private string myName;
private int? myNumber;
private bool? myBoolean;
private MyRefType myType;
public string MyName
{
get { return myName ?? "Default name"; }
set { myName= value; }
}
public int MyNumber
{
get { return myNumber ?? 42; }
set { myNumber = value; }
}
public bool MyBoolean
{
get { return myBoolean ?? true; }
set { myBoolean = value; }
}
public MyRefType MyType
{
get { return myType ?? new MyRefType(); }
set { myType = value; }
}
//optional
public MyStruct(string myName = "Default name", int myNumber = 42, bool myBoolean = true)
{
this.myType = new MyRefType();
this.myName = myName;
this.myNumber = myNumber;
this.myBoolean = myBoolean;
}
}
[TestClass]
public class MyStructTest
{
[TestMethod]
public void TestMyStruct()
{
var myStruct = default(MyStruct);
Assert.AreEqual("Default name", myStruct.MyName);
Assert.AreEqual(42, myStruct.MyNumber);
Assert.AreEqual(true, myStruct.MyBoolean);
Assert.IsNotNull(myStruct.MyType);
}
}
This may work...
public struct MyStruct
{
private bool _name;
public string myName
{
get { return (_name ? myName : "Default name"); }
set { _name = true; myName = value; }
}
private bool _num;
public int myNumber
{
get { return (_num ? myNumber : 42); }
set { _num = true; myNumber = value; }
}
private bool _bool;
public bool myBoolean
{
get { return (_bool ? myBoolean : true); }
set { _bool = true; myBoolean = value; }
}
private bool _type;
public MyRefType myType
{
get { return _type ? myType : new MyRefType(); }
set { _type = true; myType = value; }
}
}
Nevermind StackOverflowException
There is a workaround
public struct MyStruct
{
public MyStruct(int h = 1, int l = 1)
{
high = h;
low = l;
}
public int high;
public int low;
}
I've run into a really interesting runtime bug which generates a rogue stack overflow.
I've defined a structure as follows:
public enum EnumDataType { Raspberry, Orange, Pear, Apple };
public class DataRequest
{
public long DataSize
{
get { return 0; }
set { DataSize = value; }
}
public EnumDataType DataType
{
get { return EnumDataType.Apple; }
set { DataType = value; }
}
}
The following lines work perfectly:
DataRequest request = new DataRequest();
request.DataSize = 60;
However, when I step over the following line in code, it generates a stack overflow:
request.DataType = EnumDataType.Raspberry;
Of course, I can fix it by removing the defaults, or using auto get/set, but I need it to be both readable and writable, and return a default - any ideas?
public long DataSize { get { return 0; } set { DataSize = value; } }
You are constantly setting the value of DataSize. You need to create a local variable and use that instead. e.g.
private long dataSize;
public long DataSize
{
get { return this.dataSize; }
set { this.dataSize = value; }
}
EDIT
I've written DataSize but the same applies to DataType
As others have said, the stack overflow occurs because your property setter is just calling itself. It may be simpler to understand if you think of it as a method:
// This obviously recurses until it blows up
public void SetDataType(long value)
{
SetDataType(value);
}
As I understand it, you're trying to create normal properties but with a default value, right?
In that case, you need backing variables which are set by the setters - and the getters should return those variables, too. It's the variables which should get default values:
private long dataSize = 0;
public long DataSize {
get { return dataSize; }
set { dataSize = value; }
}
private EnumDataType dataType = EnumDataType.Apple;
public EnumDataType DataType {
get { return dataType; }
set { dataType = value; }
}
Alternatively, use automatic properties but set the defaults in your constructor:
public long DataSize { get; set; }
public EnumDataType DataType { get; set; }
public DataRequest()
{
DataSize = 0; // Not really required; default anyway
DataType = EnumDataType.Apple;
}
stack overflow happens because in the setter you are setting the property to a value (Ie you are trying to get something to set itself to something ... which causes an infinite loop) ... which means that it tries to set itself to a value which means its tries to set itself to a value untill boom
your properties will never get the values you are setting because they always return the same value (not the stored value)
public enum EnumDataType { Raspberry, Orange, Pear, Apple };
public class DataRequest
{
private long _dataSize = 0;
private EnumDataType _dataType = EnumDataType.Apple;
public long DataSize { get { return _dataSize ; } set { _dataSixe= value; } }
public EnumDataType DataType { get { return _dataType; } set { _dataType= value; } }
}
is what you really wanted
you have to implemet it with a backing store:
private EnumDataType dataType;
public EnumDataType DataType { get { return EnumDataType.Apple; } set { dataType = value; } }
}
You should do so anytime you do some acion in the getter and setters. By the way, why can you even set the variables? you can't read them out, you always get EnumDataType.Apple. If you want a start value, you can do like this:
private EnumDataType dataType = EnumDataType.Apple;
public EnumDataType
{
get
{
return dataType;
}
set
{
dataType = value;
}
}
I don't understand how the first line:
request.DataSize = 60;
Doesn't cause a stack overflow - my advice would be to use backing properties:
public class DataRequest
{
protected int dataSize = 0;
protected EnumDataType enumDataType;
public long DataSize { get { return 0; } set { dataSize = value; } }
public EnumDataType DataType { get { return EnumDataType.Apple; } set { enumDataType = value;}
}