string extension method for Session["key"]

At times when we access Session["key"].ToString() it gives exception when session is expired & in coding we try to access session variable. So I'm t开发者_如何学运维rying to create extension method on object class so that I could write it as Session["key"].getString() in coding so that every time I don't have to do Convert.ToString(session["key"])

Any other solutions are also appreciable.

Just use the null-coalescing operator:

string value = (session["key"] ?? String.Empty).ToString();

Update
If you must have a method to do this (extension or otherwise), I would do something like:

public static string GetValue(this HttpSessionState session, string key)
{
   // TODO: Insert appropriate error checking here.

   return (session[key] ?? String.Empty).ToString();
}

I might even go so far as to make it generic for other possible types with a GetValue call that takes a selector and then use lambdas:

public static T GetValue<T>(this HttpSessionState session, string key, Func<object, T> valueSelector)
{
    return valueSelector(session[key]);
}

public static string GetStringValue(this HttpSessionState session, string key)
{
    return session.GetValue(key, x => (x ?? String.Empty).ToString());
}

You would then use as follows:

string value = session.GetStringValue("key");

public static class ObjectExtensions
{
    public static string GetString(this object o)
    {
        if (o == null)
        {
            return string.Empty;
        }
        return Convert.ToString(o);
    }
}

and then:

string value = Session["key"].GetString();

or check this one:

public static class SessionExtensions
{
    public static string GetString(this HttpSessionStateBase session, string key)
    {
        if (session == null)
        {
            return string.Empty;
        }
        var value = session[key];
        if (value == null)
        {
            return string.Empty;
        }
        return Convert.ToString(value);
    }
}

and then:

string value = Session.GetString("key");

Maybe this can ba an alternative?

object oKey = session["key"] ?? String.Empty;
string sKey = (string)oKey;

or

string sKey = session["key"] == null ? String.Empty : (string)session["key"]

public static class ObjectExtensions
{
  public static string SafelyToString(this object o)
  {
     return o != null ? o.ToString() : string.Empty;
  }
}

This will allow Session["key"].SafelyToString()

You will not however be able to discern between an empty string in the session variable and an expired session.

I would also advise using properties for that.

protected YourType PropertyName
{
  get 
  {
    if(Session["Sessionname"] != null)
    {
      return Session["Sessionname"] as YourType;
    }
    YourType newItem = new YourType();
    // set vars
    Session["Sessionname"] = newItem;
    return newItem;
  }
  set
  {
   Session["Sessionname"] = value;
  }
}

As you can see, I chose protected as access modifier. If you want you could put it in a public class and make the property static.

Or you can use class that derives from System.Web.UI.Page.

public class MyCustomBaseClass : System.Web.UI.Page
{
   protected YourType PropertyName
   {
    // get and set like above
    }
}

Now you can replace the inheritance in your content pages from System.Web.UI.Page to MyCustomBaseClass and can easily call this.PropertyName.

Here is a easy way to access Session in Extension method:

var loggedUser = (User)System.Web.HttpContext.Current.Session["User"];