How can I create an empty one-dimensional string array?
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@Pacane Please read this.Nikita Volkov– Nikita Volkov2013-06-11 14:05:32 +00:00Commented Jun 11, 2013 at 14:05
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11 Answers
VB is 0-indexed in array declarations, so seomthing like Dim myArray(10) as String gives you 11 elements. It's a common mistake when translating from C languages.
So, for an empty array, either of the following would work:
Dim str(-1) as String ' -1 + 1 = 0, so this has 0 elements
Dim str() as String = New String() { } ' implicit size, initialized to empty
4 Comments
Ignacio Soler Garcia
I always do Dim str() as String = New String() { } because i feel that it is the best way to see that it is an EMPTY String array "{ }"
Randy Eppinger
Mark, Dim str(0) produces an array with a length of 1 with a NULL at index 0. The second, Dim str()...{ } produces an empty array with a length of zero as YonahW wanted.
Mark Brackett
@RandyEppinger is correct (and has been for the last 3 years...). str(0) does produce an array of length 1 (being 0-indexed means the length is +1 the declaration). I should've put str(-1) (which, when +1 gives you a length of 0).
default
I'm reluctant to remove half of your answer, but it is however redundant since Chris has now revised his answer. Maybe this could be reduced to only answer the question instead? Sorry for bumbing such an old thread.
Try this:
Dim strEmpty(-1) As String
5 Comments
Randy Eppinger
Upvote because it is correct. However, for clarity, I prefer Dim strEmpty() As String = New String() {} as Mark offers and SoMoS endorses. However, Mark describes two techniques that are not equivalent...see that comment.
Randy Eppinger
Update...We found the following to be equivalent and it has less ceremony: Dim myArray() = New String() {}
Slai
or to make it even more confusing -
Dim s$(-1) or Dim s$() = {}
Carl Onager
A simple Dim empty As String = {} is the most elegant version
Larry
Dim s$() = {} is hated by VB converters... The (-1) syntax is more VBish IMHO.
The array you created by Dim s(0) As String IS NOT EMPTY
In VB.Net, the subscript you use in the array is index of the last element. VB.Net by default starts indexing at 0, so you have an array that already has one element.
You should instead try using System.Collections.Specialized.StringCollection or (even better) System.Collections.Generic.List(Of String). They amount to pretty much the same thing as an array of string, except they're loads better for adding and removing items. And let's be honest: you'll rarely create an empty string array without wanting to add at least one element to it.
If you really want an empty string array, declare it like this:
Dim s As String()
or
Dim t() As String
1 Comment
Randy Eppinger
Joel, this doesn't provide the requested behavior. Each of these, t and s are Nothing. YonahW wanted an empty array which GR8DA's solution provides, although I prefer: Dim strEmpty() As String = New String() {}
Something like:
Dim myArray(9) as String
Would give you an array of 10 String references (each pointing to Nothing).
If you're not sure of the size at declaration time, you can declare a String array like this:
Dim myArray() as String
And then you can point it at a properly-sized array of Strings later:
ReDim myArray(9) as String
ZombieSheep is right about using a List if you don't know the total size and you need to dynamically populate it. In VB.NET that would be:
Dim myList as New List(Of String)
myList.Add("foo")
myList.Add("bar")
And then to get an array from that List:
myList.ToArray()
@Mark
Thanks for the correction.
Comments
You don't have to include String twice, and you don't have to use New.
Either of the following will work...
Dim strings() as String = {}
Dim strings as String() = {}
Comments
Another way of doing this:
Dim strings() As String = {}
Testing that it is an empty string array:
MessageBox.Show("count: " + strings.Count.ToString)
Will show a message box saying "count: 0".
Comments
A little verbose, but self documenting...
Dim strEmpty() As String = Enumerable.Empty(Of String).ToArray
Comments
Dim array As String() = Array.Empty(Of String)
Comments
Not sure why you'd want to, but the C# way would be
string[] newArray = new string[0];
I'm guessing that VB won't be too dissimilar to this.
If you're building an empty array so you can populate it with values later, you really should consider using
List<string>
and converting it to an array (if you really need it as an array) with
newListOfString.ToArray();
Comments
try this Dim Arraystr() as String ={}
Comments
I know this is an old thread, but another way to create an empty one-dimensional string array is to use the Array.Empty<T> method.
E.g.,
VB.NET
Dim emptyStringArray() As String = Array.Empty(Of String)()
C#
string[] emptyStringArray = Array.Empty<string>()
