Display vs Primary Key in a ListBox

tuortoam

I've come up with a creative solution to a problem I had, but I have to believe there is a better way. Here I go: Overview: Data is an XML file which I read in using ReadXML into a DataSet. For some of the GUI list boxes, I assign the datasource to a new datatable that has two columns - an "id" column that stores the Primary key for the record, and a display field, which is the way I want to present the data (for ex: display field = concatenation of firstName and lastName). I assign the displaymember to the displayfield. Problem: How do I get the primary key for future data lookups when the user clicks on the display string? My Creative Solution: When the user clicks on the listbox row, I follow these steps: 1) stop screen updates to the listbox 2) set the displayfield to the ID field in the datatable 3) get the text value of the listbox (it's now set to the primary key) 4) set the displayfield back to the displaystring 5) allow screen updates to the list box This works fine for regular windows apps, but in the compactframework, the call to stop screen updates is not allowed. So, on slow devices, you can see the contents of the listbox switch back and forth from the display field, to the primary key field, and back again. I have to believe there is an easier way.... Any takers? -Ant

4 Replies

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katana23y ago
No problem.
tuortoam23y ago
Got it. Thanks again. -Ant
tuortoam23y ago
Thanks, I'll give it it a shot. Looks like it should work in the compactframework too. -Ant

katana23y ago

Listbox.. Oh ListBox.. I like your idea, but here is a great solution, I've found. The great thing about ListBox, is they contain objects in there items list. I simply created a class w/ a valuemember (primary key) and a display member(Display), and instead of adding strings to the listbox, I add those Items. In the class, I override the ToString, and bam... it works smooth. Here is the class.

public class ColumnItem
	{
		#region Declarations
		private string m_DisplayMember;
		private long m_ValueMember;
		#endregion

		#region Constructor
		public ColumnItem(string cDisplayMember, long nValueMember)
		{
			m_DisplayMember = cDisplayMember;
			m_ValueMember = nValueMember;
		}
		#endregion

		#region Methods
		public override string ToString()
		{
			return this.m_DisplayMember;
		}
		#endregion

		#region Properties
		public string DisplayMember
		{
			get {return m_DisplayMember;}
		}
		public long ValueMember
		{
			get {return m_ValueMember;}
		}
		#endregion
	}

Here is a bit of code, for adding it to the ListBox, and I simply Cast to a ColumnItem, when i want the display member out. As so..


ListBox listBox = new ListBox(); 
listBox.Items.Clear();


DataTable table = oData.SomeTable;

for (int i = 0; i < table.Rows.Count; i++)
{
	DataRow row = table.Rows[i];
                ColumnItem item = new ColumnItem(row["display"],(long)row["key"]);

                 listBox.Items.Add(item);	
}

Now.. on the SelectIndexChanged or other events..


ColumnItem  oItem = (ColumnItem)listBox.Items[e.Index];
long Key = oItem.ValueMember;

// Do whatever from here

I hope that helps... email if you want the code in a better format. Morgan