How to interact with 2 combo boxes in c#.net 4.0 in blow case study

Question

Here i created an application consists of 2 combo boxes 1 combobox contains a list of devices & the other contains its operations.
When I select a device & its operation the equivalent unique code must be printed in Textbox1,but its givong following errors

"Index was outside the bounds of Array".

&

If i want to change the unique code for each operation as printed in textbox on clicking the button located below it what is the logic behind it to save the new ones

Attachment: filereadformsauto.rar

Vulpes · Answer

This is a bit rushed and so may not be quite right but try the following. Notice that you'll need to make some variables into fields rather than local variables so they can accessed from the textBox1_Click eventhandler. Also it's only necessary to load the Hashtable once: // these variables need to be fields rather than local variables private string[] lines = null; private Hashtable tab = null; private string path = @C:\SUBS\FileReadFormsAuto\FileReadFormsAuto\TVOP.txt; private string key = null; private void comboBox2_SelectedIndexChanged(object sender EventArgs e) { key = String.Empty; // now refers to field try { if (tab == null) // if Hashtable not yet loaded { tab = new Hashtable(); // now refers to field lines = File.ReadAllLines(path); // now refers to field foreach (string line in lines) { if (line.Contains(=)) { string[] items = line.Split('='); tab.Add(items[0] int.Parse(items[1])); } } } if (tab.ContainsKey(comboBox2.SelectedItem.ToString())) { key = comboBox2.SelectedItem.ToString(); textBox1.Text = tab[key].ToString(); } else { MessageBox.Show(Invalid Key or Command Entered....
Please Enter A Valid Command.); } } catch (Exception Ex) { MessageBox.Show(Ex.Message); } } private void button1_Click(object sender EventArgs e) { if (String.IsNullOrEmpty(key) || lines == null) return; int code; if (!int.TryParse(textBox1.Text out code)) { MessageBox.Show(Invalid code entered ....
Please enter a valid code.); textBox1.Focus(); } string search = key + =; int index = -1; for (int i = 0; i { if (lines[i].StartsWith(search)) { index = i; break; } } if (index > -1 && Convert.ToInt32(tab[key]) != code) { lines[index] = search + code.ToString(); File.WriteAllLines(path lines); // save to file tab[key] = code; // save to Hashtable MessageBox.Show(The revised code has been saved to the file.); } }