Routine is running twice

Scott Stewart

Could someone tell me why this routine runs twice?

       private void PopulateTreeView(string county)
        {
            TreeNode rootNode;
            DirectoryInfo info = new DirectoryInfo(@"C:\Users\Scot\Documents\Landman\Runsheets\" +county);
            if (info.Exists)
            {
                rootNode = new TreeNode(info.Name);
                rootNode.Tag = info;
                GetDirectories(info.GetDirectories(), rootNode);
                treeView1.Nodes.Add(rootNode);
            }
        }

        private void GetDirectories(DirectoryInfo[] subDirs,TreeNode nodeToAddTo)
        {
            TreeNode aNode;
            DirectoryInfo[] subSubDirs;
            foreach (DirectoryInfo subDir in subDirs)
            {
                aNode = new TreeNode(subDir.Name, 0, 0);
                aNode.Tag = subDir;
                aNode.ImageKey = "folder";
                subSubDirs = subDir.GetDirectories();
                if (subSubDirs.Length != 0)
                {
                    GetDirectories(subSubDirs, aNode);
                }
                nodeToAddTo.Nodes.Add(aNode);
            }
        }

I got his from an article on how to populate a treeview. The only change I made was to add a parameter to the call so I could limit the contents of the treeview. But it runs twice. When it finishes there are two top level nodes with the same name and all of the sub nodes are the same.

Thanks for your help.

6 Replies

Know the answer? Post it — somebody with the same question will find it here.

Scott Stewart14y ago
Thanks Walter and Sam. The problem fixed itself when I added an 'else' into the routine to pop a message if there were no records for a selected county.

Weird, but whatever. Time to move on to the next issue.
0
Sam Hobbs14y ago
Note that I would have suggested as Walter suggests if it got to the point where we either knew what the problem was or could not determine the problem. I prefer to be more methodical in diagnosing and solving problems. First let us determine if it is true that the SelectedIndexChanged event is firing an extra time. If it is then let us attempt to determine why and if there is a valid explanation why and if we can fix the problem by stopping the extra execution then the problem should be solved in the more appropriate manner. That way, we might solve other problems that we have not even encountered already.

The documentation of the SelectedIndexChanged event does not give a clue for why it would be fired twice. It is typical for events such as this to occur twice; once for the previous item and again for the3 new item. I do not think this is happening here but it is a possibility. I did not take the time to say that since it is irrelevant if the SelectedIndexChanged event handler is executed only once.

I do not like solving problems without understanding the problem unless I have tried to understand and am forced to give up due to time. Trying to save time by not trying to understand is likely to cost a lot of time.
0
Walter Kiess14y ago
Hi Scott,

Not sure if this will help. I have had several occasions whereby on populating a control I ended up accidentally calling the population routine again simply by the act of populating the control! Adding a control flag that says "Hey, I'm in the process of populating", checking this flag in the control's _Changed event and then resetting the flag when done may help to overcome this problem.

HTH

Walter
0
Sam Hobbs14y ago
Yes, if you try to step through the code it will be confusing. I suggest that you put a breakpoint in the tblCountiesComboBox_SelectedIndexChanged and then debug. When the breakpoint is hit, just continue. Then if the breakpoint is hit a second time then you know you do not need to analyze the code that is executed below there.
0
Scott Stewart14y ago
Hey Sam,

After I posted I thought about the call and should have included it. So here it is;

        private void tblCountiesComboBox_SelectedIndexChanged(object sender, EventArgs e)
        {
            ComboBox cboCounties = sender as ComboBox;
            string v = cboCounties.SelectedValue.ToString();
            PopulateTreeView(v);
        }

As I stepped through the routine I lost track of what loop I was on. It is recursive but I couldn't follow it. As I step through it the routine is called and runs through all the way then goes back to the calling line and runs again. Recursive calling has always posed a problem with me. Does the program automatically save it's place while the inner loop runs? the variables are named the same so how does it know what loop it is on? Whatever. I got this from the article and I am trying to figure out what calls it twice.
0
Sam Hobbs14y ago
GetDirectories is being called by PopulateTreeView and I assume that PopulateTreeView is what is being called more than once, one time more than it is supposed t be. GetDirectories is being called recursively; do you understand that? However I assume that GetDirectories is not relevant to this question.

It is nearly certain that the cause is not in the code you posted; you do not speify where PopulateTreeView is used but that is the likely cause of the problem.
0