Manage some state inside a Sharepoint WebPart

Question

Considering a simple example of a webpart that adds items to a list based on a simple button click:

public partial class MyVisualWebPartUserControl : UserControl
{
    private int cont = 0;

    protected void MyButton_Click(object sender, EventArgs e)
    {
        using (SPSite site = new SPSite("http://localhost"))
        {
            using (SPWeb web = site.OpenWeb())
            {
                SPList list = web.Lists["MyList"];
                SPListItem item = list.Items.Add();
                item["Title"] = "Title " + cont++;
                //......
            }
        }
    }
}

The title of the element, on each click of a button, should be:

Title 0
Title 1
Title 2
Title 3
Title 4
etc

Off course this isn't the case and this is outputted:

Title 0
Title 0
Title 0
Title 0
Title 0
etc

What options do I have to be able to manage such state inside the webpart?

Can I make it "per user" (each user with his own counter)?

Answer 1

When dealing with counters of any kind I like to use different approach. Even there are lots of other possibilities I like to store counter values in separated list (counter list).

In this case counter list will store value pairs: userId, current count.

Here is code:

cont =  GetNextId(SPContext.Current.Web.CurrentUser.ID);

private int GetNextId(int userId)
{
    var listName = "MyCounter";
    var nextId = 1;
    var webUrl = SPContext.Current.Web.Url;
    //Lets run things elevated
    SPSecurity.RunWithElevatedPrivileges(delegate
    {
        using (var site = new SPSite(webUrl))
        {
            using (var web = site.OpenWeb())
            {
                // Important part
                web.AllowUnsafeUpdates = true;
                var counterList = web.Lists.TryGetList(listName);
                if (counterList == null)
                {
                    // List doesn't exist
                    var listGuid = web.Lists.Add(listName, "", 
                                     SPListTemplateType.GenericList);
                    counterList = web.Lists[listGuid];
                    counterList.Fields.Add("counter", SPFieldType.Number, 
                                                        false, false, null);
                    // You can hide list
                    counterList.Hidden = true;
                    counterList.Update();
                    // You can even strip all permissions 
                    // to be sure noone can alter it
                    counterList.BreakRoleInheritance(false);
                }

                // Find user Title == UserId
                var query = new SPQuery();
                query.Query = string.Format(@"<Where><Eq><FieldRef Name=""Title""/>
                             <Value Type=""Text"">{0}</Value></Eq></Where>", userId);
                var items = counterList.GetItems(query);

                if (items.Count == 0)
                {
                    // No user. Let's create one
                    var counterNew = counterList.Items.Add();
                    counterNew["Title"] = userId;
                    counterNew["counter"] = 2;
                    counterNew.Update();
                }
                else
                {
                    // User found. Read current counter value
                    // and increment it by one
                    var result = Convert.ToInt32(items[0]["counter"].ToString());
                    var item = counterList.GetItemById(items[0].ID);
                    item["counter"] = result + 1;
                    item.Update();
                    nextId = result;
                }
                web.AllowUnsafeUpdates = false;
            }
        }
    });

    return nextId;
}

Is it overkill? Yes it is, but from past experience I can say it is bulletproof solution... almost.

Answer 2

You can use the WebBrowsable properties of a property in a web part. Like the following :

[WebBrowsable(true),
WebDisplayName("Items count"),
WebDescription("Items count"),
Personalizable(PersonalizationScope.User)]
public int Count { get; set; }

EDIT :

In the case (see the comments below) where you don't want to check-in/check-out the complete page, you could use some logic to query the list based on a simple CAML query, get the items count by user in the list, and adding +1 to that count ?

Answer 3

Not sure how well this'll work, but could you save the value of your cont variable in the ViewState bag each time you increment it?