Question

I am working with lists. I am now experimenting with determining the positions of items inside list: first, next and last. I have been able to determine the first and last position of items in my list through function getPostion and displaying the item name through a Label. Three buttons in my form: ShowFirstItem ShowNextItem and ShowLastItem show the corresponding item in a label. I am having problems for displaying the next item. I have special method for next called GetNextTree. When I am calling this method from inside ShowNextItem click I get this error: Cannot implicitly convert type 'TreeFarm.Form1.fruit_trees' to 'string'. How can avoid this error and display the item currently pointed to?

namespace TreeFarm {
     public partial class Form1: Form {
         public Form1() {
             InitializeComponent();
         }

         public class ListForTrees {


             public fruit_trees GetNextTree() {
                 //save currently pointed tree
                 fruit_trees tree = this.current_tree;
                 if (tree != null) {
                     //move current_tree to the next tree, to be returned next time
                     current_tree = current_tree.next_tree;
                     //return saved tree object
                 }
                 return tree;
             }

         }
         private void ShowNextItem_Click(object sender, EventArgs e) {
             //Show Next Item
             labelSpecificTree.Text = mainlist.GetNextTree();
         }

     }

Answer 1

You need to convert your fruit_tree to a string, and you may also want to consider the null case:

private void ShowNextItem_Click(object sender, EventArgs e)
{
    //Show Next Item
    fruit_trees nextTree = mainlist.GetNextTree();
    if (nextTree == null)
    {
        labelSpecificTree.Text = "No more trees!";
    }
    else
    {
        labelSpecificTree.Text = nextTree.ToString();
    }
}

EDIT: As MattSmith pointed out, perhaps you’d prefer to use nextTree.GetTreeType instead to match your other methods. It’s up to you.