Solved

C# DropDown smart logic implementation

Posted on 2014-10-20
8
234 Views
Last Modified: 2014-11-27
Hi Experts,

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

Dropdown selection
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]);
       }

Open in new window


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!
0
Comment
Question by:John Solomon
  • 3
  • 2
8 Comments
 
LVL 40

Expert Comment

by:Kyle Abrahams
ID: 40395225
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));
        }

Open in new window

0
 
LVL 1

Author Comment

by:John Solomon
ID: 40395368
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 :)
0
 
LVL 1

Author Comment

by:John Solomon
ID: 40395387
Hi Kyle, or an implementation like this. Thanks
0
Master Your Team's Linux and Cloud Stack

Come see why top tech companies like Mailchimp and Media Temple use Linux Academy to build their employee training programs.

 
LVL 1

Author Comment

by:John Solomon
ID: 40395409
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!
0
 
LVL 40

Accepted Solution

by:
Kyle Abrahams earned 500 total points
ID: 40395428
Hi John,

Okay, that makes a lot more sense.

What I was proposing was let's say you chose "M" . . . you would not want to see "M" in the same combo box in the values again.  That's not usually the default but I don't question people's intentions.

This should work:

PopulateCombos(ComboBox MychangedCombo)
{
    string drive1 = combo1.Text;
    string drive2 = combo2.Text;
    string drive3 = combo3.Text;
  


// populate 1 - do not populate if that's the one that was changed)
   if (MychangedCombo != combo1)
  {
     combobox1.items.Clear();
     for (int a = 0; a < drivesLetters.Count; a++)
       {
               if (drivesLetters[a] == drive2 || drivesLetters[a]  == drive3)
                    continue;
        
                  combobox1.Items.Add(drivesLetters[a]);
                   comboBox1.Text = drive1;
       }
  
//repeat for 2 && 3  
 }
}

You can then wire all 3 combo_selectedIndexchanged to:

DrivesChanged(object sender, eventargs e)
{
   PopulateCombos((ComboBox) sender);
}

Open in new window

0
 
LVL 33

Expert Comment

by:ste5an
ID: 40395788
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.
0

Featured Post

VMware Disaster Recovery and Data Protection

In this expert guide, you’ll learn about the components of a Modern Data Center. You will use cases for the value-added capabilities of Veeam®, including combining backup and replication for VMware disaster recovery and using replication for data center migration.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

When we want to run, execute or repeat a statement multiple times, a loop is necessary. This article covers the two types of loops in Python: the while loop and the for loop.
The article shows the basic steps of integrating an HTML theme template into an ASP.NET MVC project
The viewer will be introduced to the technique of using vectors in C++. The video will cover how to define a vector, store values in the vector and retrieve data from the values stored in the vector.
The viewer will be introduced to the member functions push_back and pop_back of the vector class. The video will teach the difference between the two as well as how to use each one along with its functionality.

822 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question