[RESOLVED] Null Reference Exception Help.

Hey i keep getting this null reference exception error and i can't figure out what i need to do to fix it.

I have this in the form

Code:

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        Private Sub cbLookUp_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cbLookUp.Click
        Dim webDownload As New Net.WebClient
        Dim strHtml As String
        Dim strSkillSet() As String
        Dim strSkillData() As String
        Dim i As Integer
        'Dim a As Integer
        Dim lol As Control() = clsArray.getMixedControlArray(Me, "lblHS")
        strHtml = webDownload.DownloadString(strHighscores & txtUsername.Text)
        strSkillSet = Split(LCase(strHtml), " ")
        For i = 0 To UBound(strSkillSet)
            strSkillData = Split(LCase(strSkillSet(i)), ",")
            'For a = 0 To UBound(strSkillData)
                strHSData(i).intRank = strSkillData(0)
                strHSData(i).intLevel = strSkillData(1)
                strHSData(i).intXp = strSkillData(2)
            'Next
            lol(i).Text = strHSData(i).intLevel
        Next
    End Sub

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and this in a module:

Code:

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    Public strHSData() As HighScores

    Public Structure HighScores
        Public intRank
        Public intLevel
        Public intXp
    End Structure

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Throw's the error on the first loop.
Thanks

You declare the string array strSkillData but did not assign any value to it, therefore it is nothing.
Later, you try to access it as if it already contains data, and thus you get the null reference exception.

Code:

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Dim strSkillData() As String '< at this point, strSkillData is Nothing

'Then you try to access element 0 of the array, since strSkillData is nothing, you get the exception.
strHSData(i).intRank = strSkillData(0)

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I have assigned it a value:

Code:

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strSkillData = Split(LCase(strSkillSet(i)), ",")

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Then the strHSData array is null. It's the same idea. You declared the array without giving it a dimension or assigning a value to it.

Quote:

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Originally Posted by stanav

Then the strHSData array is null. It's the same idea. You declared the array without giving it a dimension or assigning a value to it.

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hmm ok, then how do i go about assigning it a value? Because i thought:

Code:

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strHSData(i).intRank = strSkillData(0)
                strHSData(i).intLevel = strSkillData(1)
                strHSData(i).intXp = strSkillData(2)

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Would do that, is it different because i've made it a structure?

You declared strHSData as an array. Doing that creates an array with no size. You would have to dimension it to the right size to hold anything. If you don't know the size that will be needed when you start out, or if that size is changing, you should be using a List (of T) rather than an array, but even then you will have to create the list before using it.

Since you don't know the size of the array when declaring it, I suggest you to use a List(Of T) as Shaggy already said.

Code:

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Dim strHDData As New List(Of HighScores)

'Then in you loop, you do:
Dim scores As HighScores
 For i = 0 To UBound(strSkillSet)
            strSkillData = Split(LCase(strSkillSet(i)), ",")
            'For a = 0 To UBound(strSkillData)
              'Create a new HighScores
                scores = New HighScores()
                'Set its values
                scores.intRank = strSkillData(0)
                scores.intLevel = strSkillData(1)
                scores.intXp = strSkillData(2)
                'Then add it to the list
                strHDData.Add(scores)
            'Next
            lol(i).Text = strHSData(i).intLevel
        Next

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Thanks mate that worked. :)