Can't edit a settings. always null

Question

Hello I am having trouble editing my settings. I have multiple listview settings that I need to edit. I use an if statement to decide which one needs to be edited. The if statement determines the right listview and textbox but when setting the listview setting, the setting is always null. but i can read and edit just a normal text setting just fine

Note: i tred a string collection setting and had the same error

i get this error un the "Add case on the "curLV.Item.add()" line and happens for the other cases also when i have the correct code in their lol

error: "Object reference not set to an instance of an object."

public partial class Form1 : Form {
       
        //Variables
        string moviename;
        Int16 Year;
        string Res;
        string finalFileName;
        bool fileNameChack = true;
        ListView currentListview = new ListView();
        TextBox currentTextbox = new TextBox();

        //Edit the FileList
        private void AddRemClrList(object sender, EventArgs e) {

            var myButton = (Button)sender;

            //Determine listview, textbox, and sttings to work with
            
            if (myButton.Name.Contains("btngbs")) { currentListview = lvgbsSubstrings; currentTextbox = txtgbsAddString; curLV = Properties.Settings.Default.tlrString; }
            if (myButton.Name.Contains("btngbe")) { currentListview = lvgbeExtentions; currentTextbox = txtgbeAddExten; curLV = Properties.Settings.Default.tlrExt; }
            if (myButton.Name.Contains("btngbm")) { currentListview = lvgbmFolderStructre; currentTextbox = txtgbmFile; curLV = Properties.Settings.Default.folderStructure; }
            


            switch (myButton.Text.ToString()) {
                case "Add":
                    if (currentTextbox.Text.Trim().ToString() != "") {
                        currentListview.Items.Add(currentTextbox.Text);
                        curLV.Items.Add(currentTextbox.Text);
                    }
                    break;
                case "Remove":
                    foreach (ListViewItem itm in currentListview.SelectedItems) {
                        currentListview.Items.Remove(itm);
                        //StringCol.Remove(itm.Text);
                    }
                    break;
                case "Clear":
                    currentListview.Items.Clear();	
                    //StringCol.Clear();
                    break;
            }
        }
}

Answer 1

Hi,

Where this error occurs exactly, or which line of code (use break point to locate it).

---

Mitja

Answer 2

Answer 3

1. Are you sure you have initialized this listView?

2. If so, does this listView have columns?

You can try using ListViewItem class:

//for example that your listView has 2 columns:
ListViewItem lvi = new ListViewItem();
lvi.Text = "text for 1st column";
lvi.Subitems.Add("text for 2nd column"); //if you have mor e columns do the same way!
//add items to listView
listView1.Items.Add(lvi);

But 1st make sure those 2 points are true!

---

Mitja

Answer 4

I have initialized the listview. and the listview im trying to edit is actually a setting. not a visual listview. 

I get this same error when I use stringcollections so i dont think its a problem with the listview. 

Answer 5

Like a problem with the assignment of the current listview in the if statments

Answer 6

Hi,

just out of curiosity, in your example code there is no declaration of curLV.  What is it?

Also, are you sure, that one of your three

 if (myButton.Name.Contains(...

is really processed, because I can only see the assignment to curLV in this code?

---

Cheers, Dany

Answer 7

Yea i noticed that i never declared it after i posted the code. i added it and i still get the same error.

curLV is a listview setting.

and yes the if statement does get processed. it selects the right gui listbox and textbox, but when assigning the curLV which is  a settings assigned as a listbox for some reason curLV ends up being null.

Answer 8

Your user.config file is probably without your data.  After some investigation I found that ListView is not fit for this type of serialization.

In Application Settings(MSDN) you can read that

Application settings can be stored as any data type that is XML serializable or has a TypeConverter that implements ToString/ FromString.

and unfortunately ListView is not XML serializable.

You might want to do the serialization / deserialization by your own code.

I would recommend - when your list items are strings - that you join the items into a string setting and split that afterwards again to fill in your items collection.

---

Cheers, Dany