Large file into an array

Hi,
I have a large file, which i need to read into an array.
As i understand, i have to use an arrayList, but my code doesnt work. Surely there's a minor error there somewhere, cause i never used arrays much, and dont know much about their use. Anyway, here's my code:

VB Code:

Dim a As Integer = 0
        Dim List As ArrayList  
Dim ls As New StreamReader(Application.StartupPath & "/Largefile.txt")
        Dim listing As String()
        listing = ls.ReadToEnd.Split(vbNewLine)
        For Each item As String In listing
            List.Add(item)
            a += 1
        Next

The error is "object reference is not set to an instance of an object", its here: " List.Add(item)"

Thx

To fix your error:

VB Code:

Dim List As [b]New[/b] ArrayList

But I don't see why you are using an arraylist, you already have your strings in the listing array. I could be missing the point however ;)

If you're using an arraylist then you might as well read the file a line at a time:

VB Code:

Dim List As New ArrayList
Dim sr As New StreamReader(Application.StartupPath & "/Largefile.txt")
 
While sr.Peek > -1
   List.Add(sr.ReadLine())
End While
 
sr.Close()

Otherwise just do as grilkip says and keep the strings in a string array.

Quote:

---

Originally Posted by Parallax

If you're using an arraylist then you might as well read the file a line at a time:

VB Code:

Dim List As New ArrayList
Dim sr As New StreamReader(Application.StartupPath & "/Largefile.txt")
 
While sr.Peek > -1
   List.Add(sr.ReadLine())
End While
 
sr.Close()

Otherwise just do as grilkip says and keep the strings in a string array.

---

Thx, thats exactly what i needed. :thumb:

Well thats done, but now i have another problem.
Now i need have several values, and i need to check if any of them are present in the array. As i understand this code is supposed to work, but it doesnt:

VB Code:

While False
            If List.Contains("value1") Then
                MsgBox("present")
            End If
        End While

What can be the problem here?

VB Code:

'While False 'While False means it will never execute
            If List.Contains("value1") Then
                MsgBox("present")
            End If
        'End While

Quote:

---

Originally Posted by grilkip

VB Code:

'While False 'While False means it will never execute
            If List.Contains("value1") Then
                MsgBox("present")
            End If
        'End While

---

Oops... well that was stupid. :blush:
But still, i need to put it into a loop, so i only need to do this: "While True"?

depends on what you want to do, While true will start a never ending loop.

??

Quote:

---

Originally Posted by grilkip

depends on what you want to do, While true will start a never ending loop.

??

---

Yep, that's it, it must loop throu the array all the time, to see if the values are there

VB Code:

Dim vals() as string = {"list1","list2"}
For each val as string in vals
if list.contains(val) then
'whatever
end if
Next

Is your question how can you run this code all the time checking to see if the value in the list is present? You do not want to do a neverending loop, it will take all of your process time. You would simply call the sub containing the check code each time an item changes or an item is added to the list.

Are you just wanting to open the file and search for a particular line? If so, put the check in the readline method as you read in each line. If the string = the string you are searching for, you can exit the loop and close the file.

Quote:

---

Originally Posted by wild_bill

VB Code:

Dim vals() as string = {"list1","list2"}
For each val as string in vals
if list.contains(val) then
'whatever
end if
Next

---

Thx, that's exactly what i needed :thumb:

To gigemboy:
Well my app is still far from finished, so i dont know if its better to make a never ending loop or a sub, but that shouldn't be a problem now that i know how to check the array for specific values