Is there any way to auto generate a constructor which looks like this:
public class User
{
public int Id { get; set; }
public string Name { get; set; }
public User(int id, string name)
{
Id = 0;
Name = "";
}
}
Currently I am creating a constructor like that with the refactoring tool (CTRL + .):
public User(int id, string name)
{
Id = id;
Name = name;
}
and editing each line afterwards which is pretty cumbersome when you have 20 properties per class. Is there a better way to that?
(Maybe to define a code snippet, so that we can somehow read the class properties with reflection and define them as snippet parameters?)
If you have a class with 20 properties, why do you need a constructor with 20 parameters? Maybe have a sense, but I usually create constructors to initialize properties that are relevant, to simplify the code, not to set all properties.
For your class, you can set the default values when you define the property and all constructors will use this values as the default.
public class User
{
public int Id { get; set; } = 0;
public string Name { get; set; } = string.Empty;
// Here you can even omit the constructor
public User()
{
}
}
Another thing that maybe useful is define a constructor with X parameters and reuse this constructor in other constructors with less parameters:
public class User
{
public int Id { get; set; }
public string Name { get; set; }
public User()
: this(0, string.Empty)
{
}
public User(int id, string name)
{
Id = id;
Name = name;
}
}
You can replace this(0, string.Empty) for this(default, default) if you want use the default value of each type.
If you need object create with default value for properties. You can code like this:
public class User
{
public int Id { get; set; } = 0;
public string Name { get; set; } = "";
}
Purpose of quick action "generate constructor" make method contructor for assign value to fields or properties. Don't use it in the case of just assigning default values.
do you mean initialize properties? Initializing properties through the code reflection mechanism also requires one-by-one assignments. For private object properties, it is necessary to de-private encapsulation. The operation of initializing properties in c# is generally to initialize object properties or object initializers in the form of constructors. Thank you hope it helps you
class Program
{
static void Main(string[] args)
{
Student student = new Student()
{
age = 25,
name = "java",
sex = "female"
};
}
class Student
{
public int age { get; set; }
public string name { get; set; }
public string sex { get; set; }
public Student()
{
}
public Student(int age, string name,string sex)
{
this.age = age;
this.name = name;
this.sex = sex;
}
}
}
Related
I am invoking a method in my constructor like below.Is this the right way to do to set properties based on some validations.Please suggest.
public class Asset
{
public Asset(string id)
{
SetStorageId(id);
}
public string AssetId { get; set; }
public string UtilId { get; set; }
public string MappingId { get; set; }
public bool IsActive { get; set; }
private void SetStorageId(string id)
{
if (Regex.Match(id, "^[A-Z][a-zA-Z]*$").Success)
{
AssetId = id;
}
else
{
UtilId = id;
}
}
}
In my opinion your design should be like below,
You should abstract common items to base class and create specific class inheriting this,
and decide from client(consumer) which instance do you need and construct it
public class AssetBase
{
public string MappingId { get; set; }
public bool IsActive { get; set; }
}
public class Asset : AssetBase
{
public string AssetId { get; set; }
}
public class Util : AssetBase
{
public string UtilId { get; set; }
}
static void Main(string[] args)
{
string id = Console.ReadLine();
if (Regex.Match(id, "^[A-Z][a-zA-Z]*$").Success)
{
Asset asset = new Asset();
asset.AssetId = id;
}
else
{
Util util = new Util();
util.UtilId = id;
}
}
simply try this
public class Asset
{
private string id;
public string AssetId { get; set; }
public string UtilId { get; set; }
public string Id
{
set
{
if (Regex.Match(value, "^[A-Z][a-zA-Z]*$").Success)
{
this.id = value;
}
else
{
UtilId = value;
}
}
get
{
return id;
}
}
}
When you create a property in c#, a private variable is created for that property on compile time. When you try to set the Id property in the code above the Id you pass goes into the value keyword and you can perform your validations on the value keyword and set your property accordingly.
No need to complicate your code with set methods, constructors or deriving classes
or you can even use data annotations which is a more elegant way https://msdn.microsoft.com/en-us/library/system.componentmodel.dataannotations.validationattribute.aspx#Properties
using System.ComponentModel.DataAnnotations;
public class Asset
{
[RegularExpression("^[A-Z][a-zA-Z]*$")]
public string Id { get; set; }
}
It's not wrong. It can possibly grow to be a little confusing. Maybe you can make it clearer by moving the bod of SetStorageId to the constructor. Perhaps there is no need to complicate with subclassing, relative to other code within the project.
I have an application in WindowsForms and i use control propertyGrid.
I set a SelectedObject property to my custom object. But one property like this:
[CategoryAttribute("Options"), DescriptionAttribute("")]
[TypeConverter(typeof(Language))]
public List<Language> Languages { get; set; }
return me ,,Constructor type Language was not found"
Other string or enum property work fine.
There is a code of Language class:
public class Language
{
public int ID { get; set; }
public string Name { get; set; }
public string Code { get; set; }
public string ISOCode { get; set; }
public string LocaleCode { get; set; }
public Language(int id, string name, string code, string isoCode, string localeCode)
{
this.ID = id;
this.Name = name;
this.Code = code;
this.ISOCode = isoCode;
this.LocaleCode = localeCode;
}
}
Thank you for any answer
Add a default constructor like this:
public Language()
{
// Set default values or leave empty
}
I try it add previously, but i have same problem.
There is an image.
Translation
Chyba (Error)
Konstruktor typu Nextis.Eshop9.Entities.Language nebyl nalezen.
(Constructor type Nextis.Eshop9.Entities.Language was not found.)
but other properties(string, enum etc.) i can edit.
Property languages
I have this model class "UserProfile", it's the original UserProfile class of Membership with a few added properties and methods.
[Table("UserProfile")]
public class UserProfile
{
public UserProfile()
{
this.DictionaryFrom = "eng";
this.DictionaryTo = "hun";
this.trainingType = "normal";
}
[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public int UserId { get; set; }
public string UserName { get; set; }
public string DictionaryFrom { get; set; }
public string DictionaryTo { get; set; }
public string trainingType { get; set; }
public virtual ICollection<ForeignExpression> learnedexpressions { get ; set ; }
}
My problem is that upon registering a new user, the three fields in the constructor don't get the values assigned to them (so, there's a NULL in the database for each of them).
The user can set them by choosing values from a list, but I'd like to have a default value for all of them. What am I doing wrong?
Not being a C# aficionado, I'd do something like this... there's probably a "better" way of doing it.
private string myValue = "default value";
public string MyValue {
get { return myValue; }
set {
if (null != value) { myValue = value; }
}
}
Im learning c# online, and I just finished an exercise, were I should create a class called "People" and create 5 variables that can make the peoples uniqe:
public string name;
public int age;
public double heigth;
public double weigth;
public string nationality;
public int shoeSize;
I also created a class called "Bank" and declaired 4 members:
int accountNumber;
string firstName;
string lastName;
string bankName;
then, I got the question: "If you think that the bank class is associated with one person (People class) how would you use the class "People" in the class for "Bank" ?
Now I clearly didn´t understand what was being ment.. Any ideas`?
Edit: when do I need the constructor method?
That's not a constructor, that's trying to teach you that you can have classes you created as properties inside another class you create.
In their example, one person is per bank, so you could have the People class as a property called Person to signify who the account belongs to. You can do this by adding the following to your Bank class:
public People person { get; set; }
In terms of a constructor, you'd need one if you wanted to set some default properties. Consider this constructor for Bank:
public Bank()
{
accountNumber = 1;
firstName = "Default";
lastName = "Default";
bankName = "Default";
person = new People();
}
See that last line that creates person? If you removed that, but then tried to do this.person.name you'd get a NullReferenceException. That's because by default your person would have the value of null.
It could be as simple as:
public class People // I would call it person though, as People is plural
{
public int age;
public double heigth;
public double weigth;
public string nationality;
public int shoeSize;
}
public class Bank // I would call it BankAccount though
{
int accountNumber;
string firstName;
string lastName;
string bankName;
// The answer to the question:
People owner; // <-- Here the bank account has a reference to the People class,
// you provided in the constructor
// And if you need the constructor
public Bank(People owner, int accountNumber)// <-- This is the constructor
{
this.accountNumber = accountNumber;
this.owner = owner;
} // <-- The constructor ends here.
}
How about
public class Person
{
//A property for Name
//A property for Address
}
In another class a property for collection of Persons
public List<Person> People { get; set; }
Thats the way I would go:
public class Person
{
public int Age { get; set; } // I would use properties and public properties are
// starting with a great letter
public double Heigth { get; set; }
public double Weigth { get; set; }
public string Nationality { get; set; }
public int ShoeSize { get; set; }
}
public class BankAccount
{
private Person _person; // private field for the person object
public int AccountNumber { get; private set; } // public propertie for the account
// number with a private setter
// because normally you want to read
// that from the outside but not set
// from the outside
public string FirstName
{
get { return _person.FirstName; }
}
public string LastName;
{
get { return _person.LastName; }
}
public string BankName { get; set; }
public Bank(Person person, int accountNumber)
{
AccountNumber = accountNumber;
_person = person;
}
}
Please allways write down the access parameters from properties, methods etc.
Is there any way to access the Class and Property name which you attached an attribute to inside the attribute?
For example
public class User {
public string Email { get; set; }
public string FirstName { get; set; }
[MyAttribute]
public string LastName { get; set; }
}
And then in the MyAttribute class
public class MyAttributeAttribute {
public MyAttributeAttribute () : base() {
string className = /*GET CLASS NAME - should return "User" */
string propertyName = /*GET PROPERTY NAME - should return LastName*/
}
}
I know I can pass in the information in the constructor, but hoping there is an easy way somehow to save on retyping info over and over again either via reflection or...
Sorry, but no that's not possible. You could also have
public class User {
public string Email { get; set; }
public string FirstName { get; set; }
[MyAttrubute]
public string LastName { get; set; }
}
[MyAttrubute]
public class OtherClass {
[MyAttrubute]
public string AnotherProperty { get; set; }
}
The attribute can be created from anywhere. Even the following is a valid way to create an instance:
var att = new MyAttribute();
Your question could be boiled down to "Can I detect where my custom class is instantiated from?". In my last example, StackTrace could probably be used. But with attributes they are being constructed by the .NET runtime, so you would not be able to go that route.