Question

I want to copy Listbox items to StringCollection.
If the listbox items contains empty string then ignore

Why can i do this:

foreach (string item in lstModelUsers.Items)
{
    if (string.IsNullOrEmpty(item))
        continue;
    else
        Options.Default.ModelRemoveUsers.Add(item);
}

BUT not this:

foreach (string item in lstModelUsers.Items)
    string.IsNullOrEmpty(item)
        ? continue
        : Options.Default.ModelRemoveUsers.Add(item);

Although both appear equal, the inline if statement generates a syntax error.
What is the best practice?

Answer 1

You can’t use the conditional operator like that. It only accepts expressions as its operands. Your code fails to compile because continue can only be used as a statement, not an expression.

A better approach is to negate the if expression so that you don’t need the continue:

foreach (string item in lstModelUsers.Items)
{
    if (!string.IsNullOrEmpty(item))
    { 
        Options.Default.ModelRemoveUsers.Add(item);              
    }
}

You could also use Where:

var itemsToAdd = lstModelUsers.Items
    .Cast<string>()
    .Where(item => !string.IsNullOrEmpty(item));

foreach (string item in itemsToAdd)
{
    Options.Default.ModelRemoveUsers.Add(item);   
}

If you are lucky, you may even find that ModelRemoveUsers has an AddRange method, then you don’t need the loop at all:

var itemsToAdd = lstModelUsers.Items
    .Cast<string>()
    .Where(item => !string.IsNullOrEmpty(item));

Options.Default.ModelRemoveUsers.AddRange(itemsToAdd);