ASP array element is null and conversion of string to long - asp.net

Question

I've inherited an ASP project, and I'm a PHP coder with no ASP knowledge. Sorry if this post is lengthy, I just want to give as much informations as possible.
I'm struggling with this one block of code.
Dim resultArray As String()
For Each resultitem In resultArray
' Do something with each element of the array
hash.Add(dllFunctionObj.ReturnTemplateField(i), resultitem)
i = i + 1
Next
Error:
Exception!!: Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index
The solution seems simple. Check if resultitem is null then either break or skip to the next element.
So I tried this:
If IsNull(resultitem) Then
Break
End If
Error:
BC30451: Name 'IsNull' is not declared.
I tried several other alternatives I found online:
IsEmpty(resultitem) - IsEmpty not declared
String.IsNullOrEmpty(resultitem) - index out of bounds error, seems to have no effect
resultitem Is Nothing - index out of bounds
Not (Len(resultitem) > 0) - index out of bounds
Len(resultitem) = 0 - index of out bounds
The only thing that seems to come close is:
If Not resultitem Then
Break
End If
Error:
Exception!!: Conversion from string "some_string_here" to type 'Long' is not valid.
If I use Next instead of Break I get this error:
If Not resultitem Then
Next
End If
Error:
BC30081: 'If' must end with a matching 'End If'.
Help!
I'm going to include the full block of code in case it is helpful
Dim isResultArray As Boolean
isResultArray = methodInf.ReturnType.IsArray()
If isResultArray Then
Dim resultArray As String()
'*** Invoke the dll function
resultArray = methodInf.Invoke(REMem, args.ToArray)
Dim i As Integer = 0
For Each resultitem In resultArray
If Not resultitem Then
Response.Write("Found null value.")
Exit For
End If
Response.Write("i: " & i & "<br />")
hash.Add(dllFunctionObj.ReturnTemplateField(i), resultitem)
i = i + 1
' i = 6 will cause Get Constituent Name to work
'If i = 6 Then
' Exit For
'End If
Next
outputArray.Add(hash)
Else
'*** could be boolean, string, long etc.
Dim result As String
'*** Invoke the dll function
result = methodInf.Invoke(REMem, args.ToArray)
hash.Add(dllFunctionObj.ReturnTemplateField(0), result)
outputArray.Add(hash)
End If

Answer 1

You need to make sure you're not overflowing the index of the collection you're accessing. Something like this should work:
If i < dllFunctionObj.ReturnTemplateField.Length Then
hash.Add(dllFunctionObj.ReturnTemplateField(i), resultitem)
End If
Basically, you need to wrap your call to "hash.Add" in this if block to protect against accessing a value that doesn't exist.
Granted, I don't understand the purpose of the code, so you might need to handle the "else" case. But this should stop the error.

Answer 2

Looks to me like the array may be defined incorrectly.
Change this:
Dim resultArray As String()
For Each resultitem In resultArray
' Do something with each element of the array
hash.Add(dllFunctionObj.ReturnTemplateField(i), resultitem)
i = i + 1
Next
To this:
Dim resultArray() As String
For Each resultitem In resultArray()
' Do something with each element of the array
hash.Add(dllFunctionObj.ReturnTemplateField(i), resultitem)
i = i + 1
Next
Additionally, you may need to define the length of the array, e.g.:
Dim resultArray(0 to 9) As String
If the length of the array is unknown, you may define it without the minimum and maximum index, but will need to use ReDim to assign the minimum and maximum indexes later. One method would be to create the array without a length, count the items that you know will be added to the array, and then use ReDim with that count as the length of the array. For example:
Dim resultArray() As String
Dim iCount as integer 'Keep track of the count with this variable.
'Enter custom counting script here...Use a loop to count the items that will be used in the array.
ReDim resultArray(0 to iCount - 1) 'Subtract one from the iCount to match the 0-based index.
If you try to call upon a index of an array that has no set length (or use an index greater/less than the size of the array), you will most likely encounter either an "Index out of range" or "Substring out of range" error.