Question

I’m building a form application in c#. I have between 6-12 different comboboxes (varying depending on other options specific to this program, but that’s beside the point), each with the same 6 selections.

What would be the easiest way to prevent a user from selecting the same item in more than a single combobox?

Answer 1

What if you were to just create a method to handle the SelectedIndexChanged event for the combo boxes, set them all up to use the same method, and do some quick validation, like so:

private void TestUniqueSelection(object sender, System.EventArgs e)
{
      var controls = new List<System.Windows.Forms.ComboBox>();
      controls.Add(...); // <-- Add all of your controls here.

      ComboBox changedBox = (ComboBox) sender;

      if (controls
           .Where(a => a != changedBox && a.SelectedItem == changedBox.SelectedItem)
           .Count() > 0)
           MessageBox.Show("Selected Option has already been chosen");
}

Obviously you could make it more efficient by having the List<…> be a private member variable and only set it up once, but I wanted to be succinct and understandable in the sample code.