Storing and Retrieving List object in Session

hi,
see what is happening here.arraylist is a non generic collection so any type of data can be added and retrieved using its index.

but the list is generic collection so it need to have a specific type and even at the time of retrieval we need to know the type of data to be retrieved.

for the process which you are using.please use some class with the specific property and then add that property to your list.

so in this way ,you will get your data back like

public class mydata
{
public string country{get;set;}
public List<mydata> objList{get;set;}
}</mydata>

now in list--

mydata obj=new mydata();
obj.objList=new List<mydata>();
obj.objList.add(new mydata{country="India"});
</mydata>

now assign this to session

Session["Key"]=obj;

for retrieval--

mydata objlt = (mydata)Session["Key"];

for (int i = 0; i <objlt.objlist.count;>{
DropDownList1.Items.Add(objlt.objList[i].country);
}

please excuse my type mistake and the above code is just my suggestion.

you can use a property...

// List in session
public List<string> SessionList
{
    get
    {
        var obj = this.Session["myList"];
        if(obj==null) { obj = this.Session["myList"] = new List<string>(); }
        return (List<string>)obj;
    }

    set
    {
        this.Session["myList"] = value;
    }
}

your code becomes

// part 1
this.SessionList.Add("India");
this.SessionList.Add("Sri Lanka");
this.SessionList.Add("Zeebra");


// part 2
DropDownList1.Items.Clear();
foreach ( string s in this.SessionList)
{
    DropDownList1.Items.Add(s);
}

in the GET part you can see if the session is null a new list is valorized and assigned, that avoid null references.

in case you reach the code for ddl binding before valorizing the session i think you could get the null reference..