How to extract XMLElement of selectedItem of ListBox in WPF? - C# Discussion Boards

4-Apr-15 8:38

I have two buttons (button1 and button2), a List<int> and a database. When form is loading, it selects a row from database with some values and assign them value to some labels and int variables. When I click on button1, the id of the row is inserted in list as an int value (idintrebare). In List can be maximum 26 elements. Here is my problem: when I click on button2, I want to select from database, rows where idintrebare is equal with id field from table (questions), but only one row per click, and assing to the same labels and int variables values from table. If all elements from list were selected, application will exit. Here is what I tried:
First I have the list:

List<int> coada = new List<int>(26);

Function for select data:

private void selectCoada()
        {
            using (Conexiune.getConnection())
            {
                    foreach (int idi in coada)
                    {
                        string select = "SELECT DISTINCT * FROM questions WHERE id = '" + idi + "' LIMIT 1";
                        SQLiteCommand cmd = new SQLiteCommand(select, Conexiune.getConnection());
                        cmd.CommandType = CommandType.Text;
                        SQLiteDataReader rdra = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                        try
                        {
                            while (rdra.Read())
                            {
                                textBox1.Text = rdra["question"].ToString();
                                textBox2.Text = rdra["answer1"].ToString();
                                textBox3.Text = rdra["answer2"].ToString();
                                textBox4.Text = rdra["answer3"].ToString();
                                r1 = (int)rdra["option1"];
                                r2 = (int)rdra["option2"];
                                r3 = (int)rdra["option3"];
                                idintrebare = Convert.ToInt32(rdra["id"]);
                                SimulatorManager.Intrebare = textBox1.Text;
                            }
                        }
                        catch (InvalidOperationException ex)
                        {
                            MessageBox.Show(ex.Message);
                        }
                    }
            }
        }

In button1 I have just:

coada.add(idintrebare);

In button2 I have:

selectCoada();

The problem is that it selects only one value from list. I tried to use a for like this:

private void selectCoada()
        {
            using (Conexiune.getConnection())
            {
                for(int i=0;i<=coada.Count;i++) {
                    foreach (int idi in coada)
                    {
                        string select = "SELECT DISTINCT * FROM questions WHERE id = '" + idi + "' LIMIT 1";
                        SQLiteCommand cmd = new SQLiteCommand(select, Conexiune.getConnection());
                        cmd.CommandType = CommandType.Text;
                        SQLiteDataReader rdra = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                        try
                        {
                            while (rdra.Read())
                            {
                                textBox1.Text = rdra["question"].ToString();
                                textBox2.Text = rdra["answer1"].ToString();
                                textBox3.Text = rdra["answer2"].ToString();
                                textBox4.Text = rdra["answer3"].ToString();
                                r1 = (int)rdra["option1"];
                                r2 = (int)rdra["option2"];
                                r3 = (int)rdra["option3"];
                                idintrebare = Convert.ToInt32(rdra["id"]);
                                SimulatorManager.Intrebare = textBox1.Text;
                            }
                        }
                        catch (InvalidOperationException ex)
                        {
                            MessageBox.Show(ex.Message);
                        }
                    }
                }
            }
        }

, but also didn't worked.

BillWoodruff4-Apr-15 9:30

4-Apr-15 9:30

If you want to select one row each time button2 is clicked, and move through the rows in order:

private List<int> coada = new List<int>(26);

private currentIdi = 0;

// in button1 EventHandler code
if(coada.Count < 27) coada.add(idintrebare);

// in button2 EventHandler code
// good idea to show a MessageBox asking user if the really want to quit the app ?
if(currentIdi == coada.Count || currentIdi == 25) Application.Exit; // reached end of questions ?

currentIdi++;  // increment access pointer

selectCoada(coada[currentIdi]);

// selectCoada: get rid of the 'for/'foreach loops
private void selectCoada(int idi)
{
    // the code you use to fill the TextBoxes now
    using (Conexiune.getConnection())
    {
        string select = "SELECT DISTINCT * FROM questions WHERE id = '" + idi + "' LIMIT 1";
        // the rest of the code ...
    }
}

Comment: I think it's always a good idea to disable Controls when their use would cause an error, or when their use is irrelevant because the app is "not ready" to handle them. You might think about disabling 'button2 until clicking on it really can do something without an error.

«To kill an error's as good a service, sometimes better than, establishing new truth or fact.» Charles Darwin in "Prospero's Precepts"

DPaul19944-Apr-15 10:38

4-Apr-15 10:38

I receive:

Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index

DPaul19944-Apr-15 10:45

4-Apr-15 10:45

Code is good, but when all item have been passed and should show finish message, I receive that

DPaul19944-Apr-15 11:14

4-Apr-15 11:14

It's ok, I fixed it. Thank you very much for your help, I understand now Smile | :)

BillWoodruff4-Apr-15 11:17

4-Apr-15 11:17

Good

«To kill an error's as good a service, sometimes better than, establishing new truth or fact.» Charles Darwin in "Prospero's Precepts"

DPaul19945-Apr-15 0:48

5-Apr-15 0:48

Unfortunately, I still have a problem. I thought I fixed it, but I was wrong. I understand why I receive that, but I don't know how to fix it. Can you help me with that?

BillWoodruff5-Apr-15 1:48

5-Apr-15 1:48

If the problem you have now is a totally new kind of problem you haven't mentioned before, then I suggest you start a new question and include code samples, error messages, etc.

If it's the same problem you've discussed already, I suggest you add a new post to this thread and describe exactly what's not working the way you expect.

Have you stepped through your code with the debugger and isolated where the problem occurs ?

«To kill an error's as good a service, sometimes better than, establishing new truth or fact.» Charles Darwin in "Prospero's Precepts"

DPaul19945-Apr-15 3:08

5-Apr-15 3:08

Aaaa sorry, I thought you might know what problem can appear in that case. Well, On button2, you know that I call select function. Well, after last id was selected from list, I receive that error message about index. That means that the list is empty and currentIdi can't have a negative value.

modified 5-Apr-15 9:36am.

BillWoodruff5-Apr-15 10:12

5-Apr-15 10:12

Put a breakpoint in your code, and when you hit the breakpoint, use F11 to single-step through the code, observe where the error occurs.

Analyze what happened that caused the error, and then fix your code.

I think you have everything you need to get this fixed.

«To kill an error's as good a service, sometimes better than, establishing new truth or fact.» Charles Darwin in "Prospero's Precepts"

DPaul19945-Apr-15 10:16

5-Apr-15 10:16

I solved it. Sorry and thank you for your time Smile | :)

Richard Deeming7-Apr-15 2:21

Richard Deeming

7-Apr-15 2:21

Your code is vulnerable to SQL Injection[^].

NEVER use string concatenation to build a SQL query. ALWAYS use a parameterized query.

string select = "SELECT DISTINCT * FROM questions WHERE id = @id LIMIT 1";
SQLiteCommand cmd = new SQLiteCommand(select, Conexiune.getConnection());
cmd.CommandType = CommandType.Text;
cmd.Parameters.AddWithValue("@id", idi);

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

DPaul19947-Apr-15 6:43