Question

I have an object, MySession, that has a hashtable for storing arbitrary properties with arbitrary types. The relevant part of the object definition is:

public class MySession
{
    private Hashtable _sessionVars;

    /// 
    /// Set and retrieve session variables ala the traditional session managers.
    /// So, SessionObject["var1"] can be used to set or retrieve a value for var1.
    /// 
    /// Name of the variable to access.
    /// An object that was stored in the session under key.
    public object this[string key] {
        get {
            if (_sessionVars.ContainsKey(key)) {
                return this._sessionVars[key];
            }

            return null;
        }
        set {
            if (this._sessionVars.ContainsKey(key)) {
                this._sessionVars.Remove(key);
            }
            this._sessionVars[key] = value;
        }
    }
}

The annoying thing is that I have to properly cast the properties when I want to use them. For example:

MySession session = new MySession();
if ( (bool)session["valid"] == true ) { /* do something fun */ }

I would rather be able to do:

MySession session = new MySession();
if ( session["valid"] == true ) { /* do something fun */ }

Is it possible to do this in C#? If so, how?

Update: I do not want to use explicit methods for accessing the properties. The point is to be able to access them as simply as possible. Not like session.GetProperty(name, type) or something.

Answer 1

If you are using .Net Framework 4.0 then you can do it by deriving your MySession class from DynamicObject and overriding the necessary methods.

Here is the code:

public class MySession : DynamicObject
{
    //Why not use Dictionary class?
    private Hashtable _sessionVars = new Hashtable();

    public override bool TrySetMember(SetMemberBinder binder, object value)
    {
        this[binder.Name] = value;
        return true;
    }

    public override bool TryGetMember(GetMemberBinder binder, out object result)
    {
        result = this[binder.Name];
        return true;
    }

    //You can make it private so that users do not use strings directly.
    public object this[string key]
    {
        get
        {
            if (_sessionVars.ContainsKey(key))
            {
                return this._sessionVars[key];
            }

            return null;
        }
        set
        {
            if (this._sessionVars.ContainsKey(key))
            {
                this._sessionVars.Remove(key);
            }
            this._sessionVars[key] = value;
        }
    }
}

And this how you use it:

        dynamic ses = new MySession();
        ses.number = 5;
        ses.boolean = true;

        Console.WriteLine(ses.number > 4);
        if (ses.boolean)
        {
            Console.WriteLine(ses.number - 1);
        }
        Console.ReadKey();

No need for casting or using string to access the new fields! If you are using Resharper you will get intellisense for existing fields too. If you need more functionality you can override other members too.