From the following link there is an example at the bottom of the page which I have recreated in vb.net.
Before the following function runs, I save some data from a textfile into a dictionary called T.
For example:
Name - T0962
Value - 5.89
Public Shared Function initialization()
'Variables initialization
Dim parts As New List(Of Intialization)
'Add parts to the list.
parts.Add(New Intialization() With {
.PartName = "T0962",
.PartId = T.Item(.PartName))
})
If parts.Exists(Function(p) p.PartName = "T0962") Then
Dim value = parts.Where(Function(p) p.PartName = variable_type).FirstOrDefault()
Msgbox(value.PartId)
End If
End Function
The program works perfectly when I have "T0962" variable. When that variable does not exist in the textfile, it does not exist in the dictionary aswell. Thus, I get an error in the code, because the .PartId fails to be initialized. This is because in that textfile sometimes I have that value sometimes I do not.
After I have analized carefully I have noticed that the error happens in the Property statement, at Set(value As String) to be more exactly.
Public Property PartId() As String
Get
Return m_PartId
End Get
'here the error happens
Set(value As String)
m_PartId = value
End Set
End Property
Is there a way to avoid this in the Set statement? For example when there is an error then return an empty string?
Please let me know if there is something you do not understand.
Ok. Try Below. It works for me.
Dim partName As String
partName = "T0962"
parts.Add(New Intialization() With {
.PartName = partName,
.PartId = T.FirstOrDefault(Function(f) f.Key = partName).Value
})
Related
I have some code I have used many times over which has always worked great for me. The latest use, however, throws an exception under certain circumstances that I cannot seem to resolve. Here it is:
I read from a text file to an array, use it as a binding source for some of my controls (it autofills 3 controls based on the selection of a single control). I created a Student class with 4 properties (Name, ID, DOB and DOE). Here is the code I use:
Private Sub autoFill()
Dim rost As String = "Roster.txt"
Dim lines As List(Of String) = File.ReadAllLines(rost).ToList
Dim list As List(Of Student) = New List(Of Student)
For i As Integer = 0 To lines.Count - 1
Dim data As String() = lines(i).Split(":")
list.Add(New Student() With {
.StudentName = data(0),
.StudentID = data(1),
.StudentDOB = data(2),
.StudentDOE = data(3)
})
Next
StudentBindingSource.DataSource = list
End Sub
Now here is the problem. In the "For" loop when I set i to 0 to lines.count -1 it throws this error:
VB>NET EXCEPTION
However...If I change i to 1 instead of 0 it works OR if I take away data(2) and data(3) it works with i = 0. I would prefer to use 0 so that I can have a blank line in the combobox or "--choose--", etc. The only thing I have thought that might be useful is that my first row in the text file has nothing to split. Here is the line format of the text file:
Student Name ID# DOB DOE <-----This header row is NOT in the text file
Last Name, First Name : 0000000 : 01/01/2021 : 01/01/2021
I'm going to assume I'm missing something really simple here. Any guidance would be greatly appreciated! Thank you.
Before we get to the actual problem, let's re-work some things.
A better way to structure code, especially when working with data loading, is to have a method that accepts an input and returns a result. Additionally, calling ToList() or ToArray() is a very expensive operation for performance. Very often you can improve performance dramatically by working with a lower-level IEnumerable for as long as possible.
With those principles in mind, consider this code:
Private Function ReadStudentData(fileName As String) As IEnumerable(Of Student)
Dim lines As IEnumerable(Of String) = File.ReadLines(fileName)
Return lines.
Select(Function(line) line.Split(":")).
Select(Function(data)
Return New Student() With {
.StudentName = data(0),
.StudentID = data(1),
.StudentDOB = data(2),
.StudentDOE = data(3)
}
End Function)
End Function
Private Sub autoFill()
StudentBindingSource.DataSource = ReadStudentData("Roster.txt")
End Sub
Now on to the actual issue. The problem was not from looping through the list variable. The problem is the data array. At some point you have a line that doesn't have enough elements. This is common, for example, as the last line in a file.
There are many ways to address this. In some cases, the exception is already the appropriate result, because if you have bad data you really don't want to continue. In other cases you want to log the bad records, perhaps to a report you can easily review later. Or maybe you just want to ignore the error, or pre-filter for rows with the right number of columns. Here is an example of the last option:
Private Function ReadStudentData(fileName As String) As IEnumerable(Of Student)
Return File.ReadLines(fileName).
Select(Function(line) line.Split(":")).
Where(Function(data) data.Length = 4).
Select(Function(data)
Return New Student() With {
.StudentName = data(0),
.StudentID = data(1),
.StudentDOB = data(2),
.StudentDOE = data(3)
}
End Function)
End Function
Private Sub autoFill()
StudentBindingSource.DataSource = ReadStudentData("Roster.txt")
End Sub
The problem is that you didn't check 'data' to have enough elements to create the 'Student'. A simple check should fix it.
Private Sub autoFill()
Dim rost As String = "Roster.txt"
Dim lines As List(Of String) = File.ReadAllLines(rost).ToList
Dim list As List(Of Student) = New List(Of Student)
For i As Integer = 0 To lines.Count - 1
Dim data As String() = lines(i).Split(":"c)
'Check data
If data.Length >= 4 Then '
list.Add(New Student() With {
.StudentName = data(0),
.StudentID = data(1),
.StudentDOB = data(2),
.StudentDOE = data(3)
})
End If
Next
StudentBindingSource.DataSource = list
End Sub
try this code:
Dim list As List(Of Student) = New List(Of Student)(100)
basically initialize the student list with a capacity. This is the capacity of the list, not the count/length.
In my code behind in my Web project I have a Property
Public Shared UserAttributes(2) As String
Public Property _UserAttributes(ByVal Index As Integer) As String
Get
Return UserAttributes(Index)
End Get
Set(value As String)
UserAttributes(Index) = value
End Set
End Property
And I also have an ArrayList declared as Friend
Friend UserParameters As New ArrayList
I call my property like that:
_UserAttributes(0) = "parameter1"
_UserAttributes(1) = "parameter2"
_UserAttributes(2) = "parameter3"
UserParameters.Add(UserAttributes)
_UserAttributes(0) = "parameter1,1"
_UserAttributes(1) = "parameter2,1"
_UserAttributes(2) = "parameter3,1"
UserParameters.Add(UserAttributes)
From the above code we may see the two pairs of Attributes having one text each one.
What I need now is:
After I add the three Attributes from my Property to my ArrayList
The second three Attributes of my property NOT to spoil the first one.
Which by now that they are doing
And finally I have two(2) _items in my ArrayList which they have the same text on each _item (which is the last one).
What I need is to write the second (or more) set of Attributes without spoiling the previous _items from ArrayList.
Finally I've made it to solve this puzzle as follows
One Property as ArrayList
Public Property _UserParameters As ArrayList
Get
Return UserParameters
End Get
Set(value As ArrayList)
UserParameters = value
End Set
End Property
Second Property as Array
Public Property _UserAttributes(ByVal Index As Integer) As String
Get
Return UserAttributes(Index)
End Get
Set(value As String)
UserAttributes(Index) = value
End Set
End Property
And from code behind I use this code:
Dim UserAttributes As New Hashtable
Dim key As Object = Nothing
Dim Param As Object = Nothing
Dim myList As New ArrayList
Dim item As Object = UserAttributes
UserAttributes.Add("UserId", "Parametr1")
UserAttributes.Add("UserName", "Parametr2")
UserAttributes.Add("UserMail", "Parametr3")
For Each item In UserAttributes
key = item.Key
Param = item.value
logHandler._UserParameters.Add(key & "^" & Param)
Next
myList.Add(logHandler.UserParameters.ToArray)
UserAttributes.Clear()
logHandler.UserParameters.Clear()
UserAttributes.Add("UserId", "Parametr1-1")
UserAttributes.Add("UserName", "Parametr2-1")
UserAttributes.Add("UserMail", "Parametr3-1")
For Each item In UserAttributes
key = item.Key
Param = item.value
logHandler._UserParameters.Add(key & "^" & Param)
Next
myList.Add(logHandler.UserParameters.ToArray)
The use of HashTable solves my issue, Along with the conversion from HashTable parameters to String
Which add them first to the ArrayList Property
And after that add them to the second ArrayList
And the result of these ArrayList I add it to a Pull Down menu control.
And Why I'm doing all that?
That is because I have many users with the same attributes as keys but deferent values
Good day to all, with many thanks.
In the code snippet I create an array of string and want to assign it to another.
Dim rfms(0) As String
rfms(0) = "X"
The next line is not working
Me.SelectedRfms = rfms
But when I created the next function:
Function ReturnTheArrayInParamter(p() As String) As String()
ReturnTheArrayInParamter = p
End Function
This is working:
Me.SelectedRfms = ReturnTheArrayInParamter(rfms)
The definition of Me.SelectedRfms is the next:
Private pSelectedRfms() As String
''''''''''''''''''''''
' SelectedRfms property
''''''''''''''''''''''
Public Property Get SelectedRfms() As String()
SelectedRfms = pSelectedRfms
End Property
Public Property Let SelectedRfms(value() As String)
pSelectedRfms = value
End Property
Can you explain why the first one is not working and why the second is working.
You cannot assign an array declared with a fixed size to a property, use:
ReDim rfms(0) As String
(The indirect function does not use a fixed size array)
I have two lists. Both are made of structures I have defined, and this loop is meant to convert the two. I.e., convert and then add to the second list of the other type. Here is what I have:
Dim tempList As New List(Of CameraTemplateProduct)
tempList.Clear()
For j As Integer = 0 To EditCamerasNEW.templateList.Count - 1
'Set up product object.
Dim temp As New CameraTemplateProduct()
'equal properties
temp.Name = EditCamerasNEW.templateList.Item(j).mac
temp.Bitrate = EditCamerasNEW.templateList.Item(j).bitrate
temp.CamDate = EditCamerasNEW.templateList.Item(j).camdate
temp.CamTime = EditCamerasNEW.templateList.Item(j).camtime
temp.Encoder = EditCamerasNEW.templateList.Item(j).encoder
temp.FPS = EditCamerasNEW.templateList.Item(j).fps
temp.Hostname = EditCamerasNEW.templateList.Item(j).hostname
temp.MD = CBool(EditCamerasNEW.templateList.Item(j).MDen)
temp.OSD = CBool(EditCamerasNEW.templateList.Item(j).OSD)
temp.Resolution = EditCamerasNEW.templateList.Item(j).res
tempList.Add(temp)
Next
'Serialize object to a text file.
Dim x As New XmlSerializer((tempList.GetType))
x.Serialize(objStreamWriter, tempList)
Very straight forward. Copy over each property, then add it to the list. When I'm in the loop, temp's values copy over well. The values are exactly the same as the item in TemplateList. When I step through the loop, tempList is exactly what I expect it to be. Three distinct structures. But after wards I get the exact same number of items, but copies of one of them in my list.
However, the line right after the next loop, the tempList instead is the exact same count as templateList, but each value is exactly the same. So every item has the same name, MD, encoder, etc value.
What I've tried: I've tried changing the line after the next to
Dim x As New XmlSerializer((GetType(List(Of CameraTemplateProduct))))
but it gives the same result.
What am I doing wrong? Is there anything the "templist.gettype" is doing to cause this?
EDIT:
I have found that the temp is not changing property values when it loops, so it stays stuck at the first loop values. Is there a better way to clear or set it? I tried setting it to Nothing, but it gave me NULL assignment error.
EDIT2: So following the comments,
I checked to see if the templatelist items were changing. I added a
Dim test = EditCamerasNEW.templateList(j).mac
for each loop to see that it changed. The value did change. I set the rest of the "templatelist.item(j).x" to just "templatelist(j)" as above, but it didn't stop it from creating a list of repeated values.
EDIT3 Tried the below method to no avail. I'm thinking it is possibly when I create the templist of my class. It may not know how to create a list of the product? I will take any help on that.
tempList.Add(New CameraTemplateProduct With {.Name = EditCamerasNEW.templateList(j).mac, _
.Bitrate = EditCamerasNEW.templateList(j).bitrate, _
.CamDate = EditCamerasNEW.templateList(j).camdate, _
.CamTime = EditCamerasNEW.templateList(j).camtime, _
.Encoder = EditCamerasNEW.templateList(j).encoder, _
.FPS = EditCamerasNEW.templateList(j).fps, _
.Hostname = EditCamerasNEW.templateList(j).hostname, _
.MD = EditCamerasNEW.templateList(j).MDen, _
.OSD = EditCamerasNEW.templateList(j).OSD, _
.Resolution = EditCamerasNEW.templateList(j).res})
Here's a portion of the CameraTemplateProduct definition. It's pretty normal:
Public Class CameraTemplateProduct
Public Shared strhostname As String
Public Shared bOSD As Boolean
Public Shared strbitrate As String
Public Shared strencoder As String
Public Shared bMDen As Boolean 'motion detection enabled
Public Shared strres As String
Public Shared intfps As Integer
Public Shared strcamtime As String
Public Shared strcamdate As String
Public Shared strTemplateName As String
'grab properties
Public Property Name() As String
Get
Name = strTemplateName
End Get
Set(ByVal Value As String)
strTemplateName = Value
End Set
End Property
Public Property Hostname() As String
Get
Hostname = strhostname
End Get
Set(ByVal Value As String)
strhostname = Value
End Set
End Property
Public Property OSD() As Boolean
Get
OSD = bOSD
End Get
Set(ByVal Value As Boolean)
bOSD = Value
End Set
End Property
' code continues
I am trying to get a function for a class assignment to work however as the program hits the specific line in question it dies off and nothing after this line will execute. The program does not lock up, just the current execution path dies.
I have tried running debugging but much the same happens. Once I hit the link that should call a function from the object stored in the Arraylist element the break point at the actual function that should be called is not hit and nothing further happens.
Public Structure Appliances
' Create New Appliance object
Public Sub New(name As String, pusage As Double)
aName = name
aPUsage = pusage
End Sub
' Create New Washer Object
Public Sub New(name As String, pusage As Double, wusage As Double)
aName = name
aPUsage = pusage
aWUsage = wusage
End Sub
' Functions
Public Function getAName()
Return aName
End Function
Public Function getAPUsage()
Return aPUsage
End Function
Public Function getAWUsage()
Return aWUsage
End Function
Dim aName As String ' Appliance Name
Dim aPUsage As Double ' Appliane Power Usage
Dim aWUsage As Double ' Appliance Water Usage
End Structure
...
Public Class Form1
...
Dim appList As New ArrayList() ' Create an arraylist appliance objects
Public appTemp As Appliances ' To store appliance objects until they can be added to the arraylist
...
Private Function getAppInfo()
getAppInfo = Nothing
Do While fInStream.Peek() <> -1
s = fInStream.ReadLine() ' Get a line from the file and set s to it
Dim words As String() = s.Split(New Char() {","c}) ' Split the line contents along commas and set those parts into words
words(0) = words(0).Replace("_", " ") ' Reaplce underscores with spaces
If (words.Count = 3) Then ' If words contains the washer appliance
appTemp = New Appliances(words(0), Double.Parse(words(1)), Double.Parse(words(2)))
appList.Add(appTemp)
Else ' For all other appliances
appTemp = New Appliances(words(0), Double.Parse(words(1)))
appList.Add(appTemp)
End If
Loop
End Function
Private Function setUsage(name As String)
setUsage = Nothing
' Find appliance
For i = 0 To appList.Count
If (name = appList(i).getAName()) Then
If (name = "Washer") Then
s = appList(i).getWUsage() ' !!!This is the line where the execution dies at, nothing after this line is processed and the function call is not completed
txtbGPH.Text = s
End If
MsgBox("Test 1")
Exit For
ElseIf (i = appList.Count) Then
MsgBox("Appliance could not be found")
End If
Next
End Function
End Class
Use a List(Of X) instead of ArrayList if you are going to insert only one type:
Dim appList As New List(Of Appliances)
And I recommend you to declare your temp var inside the methods unless is necessary. Anyway, in this case you don't need it, you can add your var in this way:
appList.Add(New Appliances(words(0), Double.Parse(words(1))))
With this use (using lists) you won't need to use arraylistObj.Item(i).Method() and you can simply use the common way:
s = appList(i).getWUsage()
Nevermind, I figured it out just now. I did not know that arraylists are not "arraylists" but a collection. I thought maybe it would act like other collection oriented objects and that you have to use a .item(i) to access the elements, which turns out to be the case.
txtbGPH.text = appList.item(i).getAWusage()
produces the proper behavior and the rest of the code after the problematic line indicated in the OP executes as does the break point set at the called function.