Question

I have to develop a web part for SharePoint that reads a list and creates a tree view.

The tree view has to be organized as follows:
The root (or roots) is to be created by a choice field which represents a category, for instance Drinks,
the child nodes are the name of the rows that contain that category, the tree view has to be created programmatically.

List:
Title(string)       Category(Choice)
Coke            Drinks
Beer            Drinks
Fish            Food
Chips           Food

Would produce this:
Drinks
    Coke
    Beer
Food
    Fish
    Chips

code I have so far

  TreeView treeView;
    TreeNode rootNode;
    TreeNode childNode;


    protected override void RenderContents(System.Web.UI.HtmlTextWriter writer)
    {
        // render the control
        base.RenderContents(writer);
    }

    protected override void CreateChildControls()
    {
        List<TreeNode> items = new List<TreeNode>();

        base.CreateChildControls();

        // get the current site
        using (SPSite Site = new SPSite(SPContext.Current.Site.Url + "/UberWiki"))
        {
            using (SPWeb currentWeb = Site.OpenWeb())
            {

                // set the tree view properties



                SPList list = currentWeb.Lists["Pages"];

                SPFieldChoice field = (SPFieldChoice)list.Fields["Categories"];

                foreach (string str in field.Choices)
                {
                    treeView = new System.Web.UI.WebControls.TreeView();
                    rootNode = new System.Web.UI.WebControls.TreeNode(str);
                    treeView.Nodes.Add(rootNode);

                    foreach (SPListItem rows in list.Items)
                    {
                        childNode = new System.Web.UI.WebControls.TreeNode(rows.Title);
                        treeView.Nodes.Add(childNode);
                    }
                }
            }
            this.Controls.Add(treeView);
            base.CreateChildControls();
        }
    }

Answer 1

Another solution without the need to clean the multi choice string values

using (SPSite Site = new SPSite(SPContext.Current.Site.Url + "/UberWiki"))
{
    using (SPWeb currentWeb = Site.OpenWeb())
    {
        // set the tree view properties
        SPList list = currentWeb.GetList(currentWeb.Url+"/Lists/Pages");

        SPFieldChoice field = (SPFieldChoice)list.Fields["Categories"];
        treeView = new System.Web.UI.WebControls.TreeView();

        // Add root nodes
        foreach (string str in field.Choices)
        {
            rootNode = new System.Web.UI.WebControls.TreeNode(str);
            treeView.Nodes.Add(rootNode);                        
        }

        // Add child nodes
        foreach (SPListItem rows in list.Items)
        {
            childNode = new System.Web.UI.WebControls.TreeNode(rows["Title"].ToString());
            treeView.FindNode(rows["Categories"].ToString()).ChildNodes.Add(childNode);
        }
    }
    this.Controls.Add(treeView);
    base.CreateChildControls();
}