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C# DropDown smart logic implementation

Hi Experts,

I've got a ComboBox in ComboBoxStyle.DropDownList style.

This gets dunamically created based on the number of a passed parameter. The letters is an ArrayList of letters which are added to the dropdown

for (int a = i; a < drivesLetters.Count; a++)
       {
          combobox.Items.Add(drivesLetters[a]);
       }

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I've been trying to create a method so that when I click on a dropdown list, the letters which are already selected should not show up from the selections. Like on the image above, If I click on M, then M should not show up. If I select V, then V should be selected, not show on the list, M should be added.

I'm not sure how to actually do this. I wonder if I should have two ArrayLists (one holds the letters used in the dropdown, and another one to hold all the unused letters).

I am looking at an exact implementation like this (in javascript) but obviously in C#. I've tried to convert the javascript method to C#, but I was not successful.

Please kindly point me to a good starting point. I've tried so many methods, but no success..

Thanks!

Kyle Abrahams, PMP

You can use the drawItem event. (http://msdn.microsoft.com/en-us/library/system.windows.forms.combobox.drawitem(v=vs.110).aspx)

Something like:

  private void ComboBox1_DrawItem(object sender, System.Windows.Forms.DrawItemEventArgs e)
        {
            if (e.Index == ComboBox1.SelectedIndex)
                e.Graphics.FillRectangle(new SolidBrush(Color.White), new Rectangle(2,e.Bounds.Top+2, e.Bounds.Width, 0));
        }

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John Solomon

ASKER

Hi Kyle Abrahams, thank you for your answer. However, I am not sure how this method would achieve my goal.
If index is equal to combobox selectedIndex, then redraw a rectangle combobox?.

I might have confused you with my question, and I see that the javascript link was not working.. I was hoping to get something like this combo box selection implementation.

Where a number of comboboxes {combo1, combo2. combo3} are filled with a list of letters {A,B,C,D,E, F, G, H}. In order to prevent a user from choosing the same letter A in combo1 and combo3, if A is already selected in combo1, then it should not show up in combo3 dropdown. Given than letter A is unselected in combo1 and is not selected in any other comboboxes, then letter A should be available in a comboboxes dropdown as selectable.

Thank you very much for your help :)

John Solomon

ASKER

Hi Kyle, or an implementation like this. Thanks

John Solomon

ASKER

Or this is a closer implementation that I am looking for javascripcode

I'll try to learn and convert this code into C#. But your help will be greatly appreciated. :) thanks!

ASKER CERTIFIED SOLUTION

Kyle Abrahams, PMP

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ste5an

Without having a VS currently at hands, my approach would be using the MeasureItem event to set the height of the item to 0 and skip it in your own owner draw event.