Is there a way to get a specific element (based in index) from a string array using Property. I prefer using public property in place of making the string array public. I am working on C#.NET 2.0
Regards
Are you possibly trying to protect the original array; do you mean you want a protective wrapper around the array, through "a Property" (not of its own)? I'm taking this shot at guessing the details of your question. Here's a wrapper implementation for a string array. The array cannot be directly access, but only through the wrapper's indexer.
using System;
public class ArrayWrapper {
private string[] _arr;
public ArrayWrapper(string[] arr) { //ctor
_arr = arr;
}
public string this[int i] { //indexer - read only
get {
return _arr[i];
}
}
}
// SAMPLE of using the wrapper
static class Sample_Caller_Code {
static void Main() {
ArrayWrapper wrapper = new ArrayWrapper(new[] { "this", "is", "a", "test" });
string strValue = wrapper[2]; // "a"
Console.Write(strValue);
}
}
If I understand correctly what you are asking, You can use an indexer.
Indexers (C# Programming Guide)
Edit: Now that I've read the others, maybe you can expose a property that returns a copy of the array?
If the property exposes the array:
string s = obj.ArrayProp[index];
If you mean "can I have an indexed property", then no - but you can have a property that is a type with an indexer:
static class Program
{
static void Main()
{
string s = ViaArray.SomeProp[1];
string t = ViaIndexer.SomeProp[1];
}
}
static class ViaArray
{
private static readonly string[] arr = { "abc", "def" };
public static string[] SomeProp { get { return arr; } }
}
static class ViaIndexer
{
private static readonly IndexedType obj = new IndexedType();
public static IndexedType SomeProp { get { return obj; } }
}
class IndexedType
{
private static readonly string[] arr = { "abc", "def" };
public string this[int index]
{
get { return arr[index]; }
}
}
What you need is a Property that can have input (an index).
There is only one property like that, called an Indexer.
Look it up on MSDN.
A shortcut: use a built in code snippet: go to your class and type 'indexer' then press tab twice. Viola!
Properties don't take parameters, so that won't be possible.
You can build a method, for instance
public string GetStringFromIndex(int i)
{
return myStringArray[i];
}
Of course you'll probably want to do some checking in the method, but you get the idea.
I'm assuming that you have a class that has a private string array and you want to be able to get at an element of the array as a property of your class.
public class Foo
{
private string[] bar;
public string FooBar
{
get { return bar.Length > 4 ? bar[4] : null; }
}
}
This seems horribly hacky, though, so I'm either not understanding what you want or there's probably a better way to do what you want, but we'd need to know more information.
Update: If you have the index of the element from somewhere else as you indicate in your comment, you could use an indexer or simply create a method that takes the index and returns the value. I'd reserve the indexer for a class that is itself a container and use the method route otherwise.
public string GetBar( int index )
{
return bar.Length > index ? bar[index] : null;
}
Just return the array from the property; the resulting object will behave as an array, so you can index it.
E.G.:
string s = object.Names[15]
What you're asking can be done, like so:
You can initialize an object that holds your array, giving you exactly what you need:
public class ArrayIndexer<T> {
private T[] myArrRef;
public ArrayIndexer(ref T[] arrRef) {
myArrRef = arrRef;
}
public T this [int index] {
get { return myArrRef[index]; }
}
}
Then, in your class:
public ArrayIndexer arr;
private SomeType[] _arr;
//Constructor:
public MyClass(){
arr = new ArrayIndexer<SomeType>(ref _arr);
}
Usage:
myClassObj.arr[2] // Gives the second item in the array.
Et Voila! An indexed property.
Related
I want to be able to do something like
public string[]|string stringsOrSingleString;
I want to create a variable that can be an array or a non-array of a specific type (a string in the example).
Example usage
I want to be able to do stringsOrSingleString = "bla" or stringsOrSingleString = new string[] { "bla" };
Do I need a custom class to do this? Preferably, I don't want to use a custom class, but if necessary then ok.
I should be able to tell later on if the value assigned was an array or non-array, using typeof or is, or something.
The whole reason for this ordeal is that I have a javascript API(that I didn't create), and I am trying to make a C# api that follows the JS api/syntax as close as possible.
Is this possible?
May be you want something like this?
public class Item<T>
{
public T Value => this.Values.Length > 0 ? this.Values[0] : default(T);
public T[] Values { get; set; }
}
The class has an array of values and a single value. There are some implementations like this, for example, when you select files with OpenFileDialog: you have a list of files (for MultiSelect case) and also a single SelectedFile. My answer is focused with this in mind. If you need another thing, give more information.
UPDATE
You can update previous class in this way:
public class Item<T>
{
public T Value => this.Values.Length > 0 ? this.Values[0] : default(T);
public T[] Values { get; set; }
public T this[int index] => this.Values[index];
public static implicit operator Item<T>(T value)
{
return new Item<T> { Values = new[] { value } };
}
public static implicit operator Item<T>(List<T> values)
{
return new Item<T> { Values = values.ToArray() };
}
public static implicit operator Item<T>(T[] values)
{
return new Item<T> { Values = values };
}
}
Example usage:
Item<string> item = "Item1";
string text = item.Value;
string sameText = item[0];
Item<string> items = new[] { "Item1", "Item2" };
string[] texts = item.Values;
string item1 = item[0];
string item2 = item[1];
You can create an instance using a simple object or an array. You can access to the first value using Value property and to all items using Values. Or use the indexer property to access to any item.
In C# you need to know the type of the variable. It's difficult work in the same form of JavaScript. They are very different languages.
I'm trying to do this with Dictionary, Array seems more general so I'm using it as an example.
Class MyArray
{
private Array array;
public Array [p] // a property
{
get {return array[p]};
set
{
array[p] = value;
more_stuff();
}
}
}
This is sudo-code. I've included only a part of the class, where my problem would be. Can I use a property as above, or another structure to achieve this?
(new MyArray[]{4, 3, 1, 5})[2] = 4;
You're looking for an indexer.
So you're class should look like this:
class MyArray<T>
{
private T[] array = new T[100];
public T this[int p]
{
get
{
return array[p];
}
set
{
array[p] = value;
// more_stuff();
}
}
}
To be able to use a collection initializer (e.g. new MyArray<int>{4, 3, 1, 5}), your class has to implement IEnumerable and provide a Add method.
I'm trying to make an object to hold some strings. The object can be anything, including collections, arrays ... The strings need to be enumerable (IEnumerable or similar). Each string indexer needs to be known by intellisense and Reflection is a last option. One single object, no separate object for indexers.
Example usage:
public static class features
{
public const string favorite = "blue background";
public const string nice = "animation";
}
public static class Program
{
public static void Main()
{
foreach (string feature in features)
{
Console.WriteLine(feature);
}
//... select a feature
Console.WriteLine(features.favorite);
}
}
EDIT:
I will use the first solution proposed by Jim Mischel, modified to use reflection, as that gets the advantages I'm interested in at the current time.
encapsulates everything in one entity
names are directly associated with values
enumerator is dynamic
public IEnumerator<string> GetEnumerator()
{
FieldInfo[] strings = this.GetType().GetFields();
foreach (FieldInfo currentField in strings)
{
yield return currentField.GetValue(null).ToString();
}
yield break;
}
I thank everyone for your effort.
Offhand, I can think of two ways to do it. However, since it must be IEnumerable<string> it can't be a static class because static classes can't implement interfaces. Nor can static methods implement interface methods.
The first way uses constants and an enumerator that just returns them in order:
public class Features: IEnumerable<string>
{
public const string Favorite = "blue background";
public const string Nice = "animation";
public IEnumerator<string> GetEnumerator()
{
yield return Favorite;
yield return Nice;
}
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
}
The second way stores the values in an array and uses an enum for the indexes. The enumerator just returns the enumerator for the array. Again, this is not static because of the enumerator, and also because indexers can't be static.
public enum FeaturesIndex
{
Favorite = 0,
Nice = 1
}
public class Features2 : IEnumerable<string>
{
private static readonly string[] _features = new string[]
{
"blue background",
"animation"
};
public string this [FeaturesIndex ix]
{
get { return _features[(int) ix]; }
}
public IEnumerator<string> GetEnumerator()
{
return ((IEnumerable<string>) _features).GetEnumerator();
}
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
}
A third possibility, as pointed out by others, is using a dictionary and either an enumeration or defined constants as keys. It's an interesting approach, the only potential drawback being that you can't guarantee the order in which keys will be returned when you enumerate the collection. If that's a problem, you could have your enumerator sort the sequence before returning.
Any way you look at it, there are tradeoffs. Both of my solutions require manual synchronization of keys and values. In the first, you have to make sure that the enumerator retures all of the values. In the second, you have to ensure that your enum matches the array.
Pick your poison.
It also depends on how you're going to use the thing. My first solution has the benefit of simplicity and would probably be quite acceptable if it's a write-once, use-forever kind of thing. The second option has the benefit of using an indexer, which is more commonly associated with collections.
There are many better ways to do this. To follow a similar pattern to what you're looking for, here's one way of doing it:
public static class features
{
public enum TYPES { favorite, nice }
public static Dictionary<TYPES,string> values = new Dictionary<TYPES,string>() {
{ TYPES.favorite, "blue background" },
{ TYPES.nice, "animation" } };
}
public static class Program
{
public static void Main()
{
foreach (string feature in features.values.keys)
{
Console.WriteLine(features.values[feature]);
}
//... select a feature
Console.WriteLine(features.values[TYPES.favorite]);
}
}
So really what you are asking for is an object with Properties you can change and is also enumerable, but makes it so you don't need to call reflection to enumerate unless absolutely necessary.
If what I assume you are actually looking is the following
public class Features: IEnumerable<string>
{
private readonly Dictionary<string,string> _internalCollection;
public Features()
{
_internalCollection = new Dictionary<string,string>();
}
private string GetByKey(string id)
{
if(!_internalCollection.ContainsKey(id))
return null;
return _internalCollection[id];
}
private void SetByKey(string id, string value)
{
_internalCollection[id]=value;
}
const string _favoriteId = "favorite";
public string Favorite
{
get { return GetByKey(_favoriteId); }
set { return SetByKey(_favoriteId,value);}
}
const string _niceId = "nice";
public string Nice
{
get { return GetByKey(_niceId);}
set { return SetByKey(_niceId, value);}
}
public string this[string index]
{
get { return GetByKey(index.ToLower()); }
set { return SetByKey(index.ToLower(), value);}
}
public IEnumerator<string> GetEnumerator()
{
foreach(var key in _internalCollection.Keys)
yield return _internalCollection[key];
yield break;
}
}
I'm trying to convert an object array of my class to a string array.
In this example I have two classes. In one of my classes I want to creat two variables, objects of the other class. On variable will be a array and the other a "regular" variable.
Two classes name. ShowResult and Game.
In the Game class I write:
private ShowResult[] _showResults;
private ShowResult _showResult;
In my properties in my Game class I try to convert this two variables to string array and string:
public string[] ShowResults
{
get { return _showResults.ToString().ToArray(); }
set { _showResults.ToString().ToArray() = value; }
}
public string ShowResult
{
get { return _showResult.ToString(); }
set { _showResult = value; }
}
This doesn't work. I really want my custom object to be converted to string array and to string. But I get an error.. I know I can, but I don't know just how..
If anyone has any suggestion I would be greatful. OBS, this is just an example. But still I don't get why it wont work..?
By the way, sorry for my bad english. ;)
Best regards
Try this:
_showResults.Select(a => a.ToString()).ToArray()
Given the nature of your code (i.e. strings appear to map directly to ShowResults instances), you might want to consider implementing implicit operators:
ShowResults s = "hello";
string ss = s;
Console.WriteLine(ss); // "hello"
class ShowResults
{
public string SomeProp
{
get; private set;
}
public static implicit operator ShowResults(string s)
{
//this is where you'd parse your string
//to form a valid ShowResults
return new ShowResults{SomeProp = s};
}
public static implicit operator string(ShowResults s)
{
return s.SomeProp;
}
}
How do square brackets in a method declaration fit in with c#? That is I see when reading up on WPF validation one can use IDataErrorInfo with an example of the following.
public string this[string propertyName]
// Error handling takes place here.
public string this[string propertyName] // <== IE HERE
{
get
// etc
}
}
I note MSDN says "Square brackets ([]) are used for arrays, indexers, and attributes. They can also be used with pointers." So is the above usage a pointer?
This is a standard feature of the C# language called an Indexer. Generally you would use these when writing your own collections, or similar types. Here is a brief (not real world) example.
public class Foo {
private List<int> m_Numbers = new List<int>();
public int this[int index] {
get {
return m_Numbers[index];
}
set {
m_Numbers[index] = value;
}
}
}
class Program {
static void Main() {
Foo foo = new Foo();
foo[0] = 1;
}
}
There's a lot of cool things you can use indexers for if you are creative, it's a really neat feature of the language.
This is a declaration of an Indexer. It's analagous to array indexing. propertyName is a string which the method uses to index into some kind of collection. The method returns the corresponding string from the collection.
Of course, the method could do something else, but that's what the semantics mean.
That would be an indexer property. They're useful on custom collections:
public class MyCustomCollection
{
List<MyObject> _list = new List<MyObject>();
public string this[string name]
{
get { return _list.Single(o => o.Name == name)
.Select(o => o.Description);
}
public string this[int id]
{
get { return _list.Single(o => o.Id == id).Select(o => o.Description);
}
}
And then you can use the collection like:
MyCollection col = new MyCollection();
// Fill the collection
string description = col["Name"];
string description2 = col[2];