Slow showing / drawing dialogue with ListBox?

Question

My application uses entity framework to pull in a small tiny set of results... It takes about 3 seconds for it to do it? Why might this be?

Start.cs

Answer 1

Changing my IEnumerable to IList made a difference:

public static class PreLoadedResources
{
    public static IEnumerable<ProjectType> projectTypes;
}

to

public static class PreLoadedResources
{
    public static IList<ProjectType> projectTypes;
}

then in my loading (which takes a 2 second hit), I just .ToList it instead... but now the showdialogue procedure takes split seconds.

Answer 2

The ListBox has to redraw every time you add an item. You can either use Dmitry's method of using AddRange(), or you can wrap your loop with BeginUpdate()/EndUpdate() calls.

ListBoxProjectType.BeginUpdate();

foreach( var projectType in projectTypes )
{
    ListBoxProjectType.Items.Add(projectType.Title);
}

ListBoxProjectType.EndUpdate();

Answer 3

Try to replace adding individual items to listbox with AddRange:

public void ListBoxProjectTypes()
{
    IEnumerable<ProjectType> projectTypes = projectTypeRepository.ProjectTypes;
    ListBoxProjectType.Items.AddRange(projectTypes.Select(item => (object)item.Title).ToArray());
}

Or simply wrap items adding with ListBoxProjectType.BeginUpdate and ListBoxProjectType.EndUpdate.