Using the typical get set properties in C#... with parameters

Question

Hello,

I'd like to do the same in C#. Is there anyway of using properties in C# with parameters in the same way I've done with the parameter 'Key' in this VB.NET example?

Private Shared m_Dictionary As IDictionary(Of String, Object) = New Dictionary(Of String, Object)

Public Shared Property DictionaryElement(ByVal Key As String) As Object
    Get
        If m_Dictionary.ContainsKey(Key) Then
            Return m_Dictionary(Key)
        Else
            Return [String].Empty
        End If
    End Get
    Set(ByVal value As Object)
        If m_Dictionary.ContainsKey(Key) Then
            m_Dictionary(Key) = value
        Else
            m_Dictionary.Add(Key, value)
        End If

    End Set
End Property

Thanks

Answer 1

Is there anyway of using properties in C# with parameters

No. You only can provide the default property in C# with an argument, to model indexed access (as in a dictionary):

public T this[string key] {
    get { return m_Dictionary[key]; }
    set { m_Dictionary[key] = value; }
}

Other properties can't have arguments. Use a function instead. By the way, it's recommented to do the same in VB so other .NET languages (C# …) can use your code.

By the way, your code is unnecessarily complicated. Four things:

• You don't need to escape the String identifier. Use the keyword directly.
• Why not use ""?
• Use TryGetValue, it's faster. You query the dictionary twice.
• Your setter doesn't have to test whether the value already exists.

---

Public Shared Property DictionaryElement(ByVal Key As String) As Object
    Get
        Dim ret As String
        If m_Dictionary.TryGetValue(Key, ret) Then Return ret
        Return "" ' Same as String.Empty! '
    End Get
    Set(ByVal value As Object)
        m_Dictionary(Key) = value
    End Set
End Property

Answer 2

Your code sample strikes me as a very strange design and an abuse of what properties are intended for. Why not just an instance method AddOrUpdateKey:

Public Sub AddOrUpdateKey(ByVal Key As String, ByVal Value as Object)
    If m_Dictionary.ContainsKey(Key) Then
        m_Dictionary(Key) = Value
    Else
        m_Dictionary.Add(Key, Value)
    End If
End Sub

Your property also returns String.Empty if the key does not exist, but claims to return an Object, nor a String.

Answer 3

The "proper" way to do it in C# is to create child class specifically to access the collection. It should either hold the collection itself or have internal linkages to the parent class.

Answer 4

Here is a sample for you (with changes along the lines of Grauenwolf's suggestions):

using System;
using System.Collections.Generic;

public class Test
{
    public FakeIndexedPropertyInCSharp DictionaryElement { get; set; }

    public Test()
    {
        DictionaryElement = new FakeIndexedPropertyInCSharp();
    }

    public class FakeIndexedPropertyInCSharp
    {
        private Dictionary<string, object> m_Dictionary = new Dictionary<string, object>();

        public object this[string index]
        {
            get 
            {
                object result;
                return m_Dictionary.TryGetValue(index, out result) ? result : null;
            }
            set 
            {
                m_Dictionary[index] = value; 
            }
        }
    }


}

class Program
{
    static void Main(string[] args)
    {
        Test t = new Test();
        t.DictionaryElement["hello"] = "world";
        Console.WriteLine(t.DictionaryElement["hello"]);
    }
}

Answer 5

Thanks Konrad, Alan, Grauenwolf,

In conclusion, I can't use C# properties exactly in the same way that in VB.NET... :_( Anyway, your answers has been very usefull to me, and I´ll probably take this ideas to my C# code.

In addition to the answers to the properties question, there are other good points. For example,

• Use TryGetValue, it's faster. You query the dictionary twice.
• Your setter doesn't have to test whether the value already exists.

Thanks Sören, too, using a method don't fits well in my initial aims, but thanks very much.

Answer 6

Very good Hasni

Answer 7

all the steps about get and set please vguys