Can a ComboBox accommodate both numbers and text?

Question

I am trying to figure out something. I have a method which adds some items into a ComboBox named "cbSize". I realize that if I add two types of data into it, the code will crash. Is this because a ComboBox can only accommodate one type of data?

items.Add(1);
items.Add(10);
items.Add(100);
items.Add(2);
items.Add(20);
items.Add(3);
items.Add(30);       //works fine if add numbers only

//items.Add("4");    //will crash if mix both numbers and text
//items.Add("2");    //works fine if add text only

//then sort them out
items.Sort();

//now clear original cbSize items
cbSize.Items.Clear();

//and add them back in sorted order
cbSize.Items.AddRange(items.ToArray());

//gotta clear ArrayList for the next time or else things will add up
items.Clear();

At what point does the exception occur? – cdhowie Jun 13 '12 at 17:37 — cdhowie, Jun 13 '12 at 17:37

score 2 · Accepted Answer · edited May 23 '17 at 12:03

Is this because a ComboBox can only accommodate one type of data?

No, try below it will work

cbSize.Items.Add("44");
cbSize.Items.Add(44);

problem is with your items collection, it is type safe. you can't add different types to it.

try with list of objects. it will work. reason is both int and string are objects

List<object> items = new List<object>();
items.Add(1);
items.Add(30);     
items.Add("4");    
items.Add("2");    

//since you have string and int value you need to create custom comparer
items.Sort((x, y) => Convert.ToInt32(x).CompareTo(Convert.ToInt32(y)));

//now clear original cbSize items
cbSize.Items.Clear();

//and add them back in sorted order
cbSize.Items.AddRange(items.ToArray());

OR you can use ArrayList class (not type-safe because it can store any object)

var integers = new ArrayList();
integers.Add(1);
integers.Add(2);
integers.Add("3");
comboBox1.Items.AddRange(integers.ToArray());

What is type-safe in .net?

Thank you Damith. In fact, I define 'items' as an 'ArrayList' to perform the sorting. I am importing the values from a 'Textbox', so I guess it is best to keep them as text. Anyways, your answer is very helpful. I love answers that go down to the root of the problem. It should help me whenever I cannot avoid having 2 types of data. — CaTx, Jun 13 '12 at 18:53

score 0 · Answer 2 · answered Jun 13 '12 at 17:46

Yes. What you can do is to provide a Size class that will adapt from ints and strings:

items.Add(new Size(3));
items.Add(new Size(4));
items.Add(new Size("large"));

Then, you could make the Size class implement IComparable so you can call the Sort() method.

Can a ComboBox accommodate both numbers and text?

2 Answers2