While working on a project for ImageSource, I recently found an interesting quirk when using the .NET Windows form combobox control. The issue occurred when I was populating the combobox’s item list with a datasource. The data was populating at a very slow rate, slower than it was taking to retrieve the data I was using to populate it from the database. The code I was using looked something like this:
Dim tbl As DataTable = _dataSource.ReadAllItemsFromDbTable()cboComboBox.DataSource = tbl cboComboBox.DisplayMember = "Name" cboComboBox.ValueMember = "Value"
What I later found out was that the ordering of the above code made all the difference, and that by setting the DisplayMember property after setting the DataSource property, I was causing the combobox to reload all of the item data a second time. To stop it from doubling all of the work, I just had to make a simple code change. This involved moving the setting of the DisplayMember and ValueMember properties above the setting of the DataSource property.
Dim tbl As DataTable = _dataSource.ReadAllItemsFromDbTable()cboComboBox.DisplayMember = "Name" cboComboBox.ValueMember = "Value" cboComboBox.DataSource = tbl
This fixed the issue, as the DisplayMember property is now already set before all of the items are loaded. I hope this helps fix any issue you may have had with this control.