get text from ComboBox

You can but this is wrong approach.

The right approach is: don't store strings in the list of the ComboBox, store instances of some class or structure:

class ItemHelper {
    internal ItemHelper(string name, int id) {
        this.fName = name; this.fId = id;
    }
    public override void ToString() {
        return string.Format("{0}:{1}", this.fId, this.fName);
    }
    internal Name { get { return fName; } }
    internal Id { get { return fId; } }
    string fName;
    int fId;
}

Why ToString is overridden? To define how the item is presented in the string form when added to the list (of ComboBox or any other list, also a TreeView).

This way, you can access to the Id directly, without any string tricks, in a reliable way. Well, you will need to cast the item you need to ItemHelper.

—SA