Question

I have a list of strings. For each string in that list, I want to prepend another string. I wrote a method to do it, but I was wondering if there was something already in .NET I could use to do this. It seems like something that could be built in, but I was not able to find anything.

Here is the method I wrote:

Private Function PrependToAllInList(ByRef inputList As List(Of String), ByRef prependString As String) As List(Of String)
    Dim returnList As List(Of String) = New List(Of String)
    For Each inputString As String In inputList
        returnList.Add(String.Format("{0}{1}", prependString, inputString))
    Next
    Return returnList
End Function

It works, but I would rather use built in functions whenever possible. Thanks for your help.

Answer 1

If you can use LINQ (.NET 3.5 or greater), you can use a simple LINQ query to do the work for you:

Dim qry = stringList.Select(Function(s) "prepend this " & s)
Dim returnList = qry.ToList()

By default, Select() will return an IEnumerable(Of String), which should work. If you really need the collection to be a list, you can include the .ToList() command. However, if you only plan to iterate over the collection (e.g. For Each s As String in qry), there’s no need to take on the expense of converting it back to a list.