Fejl ved split

Nedenstående kode genererer fejlen "Object reference not set to an instance of an object." i linien
arrCategories = strCategories.Split(",")



        Dim DbConnect As New DataAccess.objDataAccess()
        Dim DsCategories As New DataSet()
        DsCategories = DbConnect.RunSPReturnDS("Select_Categories", "Categories", New SqlParameter("@CategoryId", -1))
        Dim intRecordCount As Integer
        Dim intLoop As Integer
        Dim intCurItem = 0
        Dim intIndent As Integer
        Dim strIndent As String
        Dim strCategories As String
        intRecordCount = DsCategories.Tables(0).Rows.Count
        For intLoop = 0 To intRecordCount - 1
            If CInt(DsCategories.Tables(0).Rows(intLoop)("ParentCategoryId")) = CInt(intCurrentId) Then
                For intIndent = 1 To IntDepth
                    strIndent = strIndent & "  "
                Next
                strCategories = strCategories & (DsCategories.Tables(0).Rows(intLoop)("CategoryId")) & "," & strIndent & DsCategories.Tables(0).Rows(intLoop)("Description") & ","
                strCategories = strCategories & GetCategories(CInt(DsCategories.Tables(0).Rows(intLoop)("CategoryId")), IntDepth + 1)
            End If
        Next
        Dim arrCategories() As String
        arrCategories = strCategories.Split(",")