where does it go wrong?
my coding
Imports Newtonsoft.Json
Imports Newtonsoft.Json.Linq
Imports System.Net
Public Class DigiposAJA
Private Sub CekPaket()
Dim json As String = (New WebClient).DownloadString("http://192.168.101.1:100/list_product?username=SIP12&category=ROAMING&to=0811&payment_method=LINKAJA&json=1")
Dim jarr As JArray = Linq.JArray.Parse(json)
Dim sKatagori As String
For Each jtk As JToken In jarr
sKatagori = jtk.SelectToken("kategori")
DgvDigipos.Rows.Add()
DgvDigipos.Rows(DgvDigipos.Rows.Count - 1).Cells("DgvKategori").Value = sKatagori
Next
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
CekPaket()
End Sub
End Class
after I debug the result is an error like this.
Newtonsoft.Json.JsonReaderException: 'Error reading JArray from JsonReader. Current JsonReader item is not an array: StartObject. Path '', line 1, position 1.'
Can you help me to get a great result
Most likely this is a result of your call to the web service not returning the result you expect.
This is actually a good example of the benefits of separation of concerns and strongly typed objects. Your sub CekPaket should be broken down into 3 parts. 1) get the string. This should be a function and should use some sort of configuration to get the end point and have appropriate guards for failure, 2) parse the string into a strongly typed object (IEnumerable of whatever), this should validation to make sure that the input is good. You might want to make this function public for easy testing. And finally 3) bind your results to your UI. It looks like you are doing this part by hand, whenever possible you should allow the frame work to do this for you by providing a data source and a template for the display.
Related
Here is my array:
Public RacersArray(AmountOfRacers - 1) As Racer
<Serializable()> Public Structure Racer
Public Name As String
Public CleatSize As String
Public SkillLevel As String
Public Height As String
Public Team As String
Public CompatibilityArr() As String
End Structure
<Serializable()> Public Structure Compatibility
Public Name As String
Public Score As Integer
End Structure
Below is the code I am using to try save and load from file. The file is getting populated with what looks like the correct gibberish, but when loading the array and it's indexes are still 'nothing'
Public Sub RacersInputSAVE()
Dim bf As New System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
Dim fStream As New FileStream(SaveLocation, FileMode.Create)
bf.Serialize(fStream, InputRacers.RacersArray) ' write to file
fStream.Close()
End Sub
Public Sub RacersInputLOAD()
Dim bf As New System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
Dim fStream As New FileStream(LoadLocation, FileMode.Open)
InputRacers.RacersArray = bf.Deserialize(fStream) ' read from file
fStream.Close()
End Sub
The first thing that is probably wrong is this:
Public CompatibilityArr() As String
Based on the names it seems like that is supposed to be that second Compatibility structure. If so, it should be:
Public CompatibilityArr As Compatibility()
Its not clear if that is part of the problem being described (but when loading the array and it's indexes are still 'nothing' is vague since there is more than one array). Otherwise the second structure isnt being used.
Next, set Option Strict On. When deserializing, the BinaryFormatter always returns Object which needs to be cast to the correct Type:
Racers = DirectCast(bf.Deserialize(fs), Racer()) ' read from file
With those 2 changes, all the data made the round trip fine for me.
Third, Structure is not the right Type for that. Those should be classes, and rather than public Fields/Members, use Properties especially if there will be any data binding involved:
<Serializable()>
Public Class Racer
Public Property Name As String
...
Also, anything which implements a Dispose()method, like a FileStream should be used in a Using block which will close and dispose of the target object:
Dim bf As New BinaryFormatter
Using fs As New FileStream(fileName, FileMode.Create)
bf.Serialize(fs, Racers) ' write to file
End Using
Finally, you would probably find some of the NET collections such as List(Of Racer) to be easier to work with than arrays. It takes about 15 mins to learn how they work.
MSDN: Choosing Between Class and Struct
For some reason, I have never had good luck serializing to a file using the BinaryFormatter. The exact reasons are lost to the mists of time, but I do know that SoapFormatter works correctly for me:
Using oStream As Stream = File.Open(SaveLocation, FileMode.Create, IO.FileAccess.Write)
If oStream IsNot Nothing Then
Call (New System.Runtime.Serialization.Formatters.Soap.SoapFormatter).Serialize(oStream, InputRacers.RacersArray)
End If
End Using
I've been thoroughly combing StackOverflow and other sources for the answers to these problems, and have not been able to find a solution that would work cohesively with the steps I need to accomplish.
Things I need to do:
Create an array from a text file and display in a listbox (this is done and works)
Have user fill in a text box, click a button, and the array is searched for anything matching the text box's value
Have the results of the search displayed in a separate listbox
Here's what I've got so far, and it's fairly hacked together, so if there's anything that can be improved, naturally, I'd be all for that.
`
Public Class Form1
Dim lblName As Object
Public colleges As String
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim colleges() As String = IO.File.ReadAllLines("Colleges.txt")
ListBoxCollege.Items.AddRange(colleges)
End Sub
Private Sub btnSearchGo_Click(sender As Object, e As EventArgs) Handles btnSearchGo.Click
Dim n As Integer, college As String
college = txtCollegeSearchUserInput.Text
n = Array.IndexOf(colleges(), college)
If n <> 1 Then
[[Needs to output into new listbox, preferably here]]
End If
End Sub
If there's anything else needed from VB, I can provide if necessary!
In your case you can do something like this
For i As Integer = 0 To ListBoxCollege.Items.Count -1
If ListBoxCollege.Items(i).ToString().IndexOf(college, StringComparison.OrdinalIgnoreCase) > -1 Then
findList.Items.Add(ListBoxCollege.Items(i))
End If
Next
The difference here - you calling IndexOf on array and I call it for each item in list. Therefore I return all matches, while you only the first one
This is little bit limited in search criteria. You could use regex as well for wild cards etc. Or you store your data (colleges) in System.Data.DataTable, and you would be able to run Sql Select queries on it almost like in database.
Please have a look at the code below:
Imports System.Data.Common
Imports System.Data.SqlClient
Imports System.Data.OracleClient
Public Class clsParameterValues
Implements IDisposable
Private paramValues(0) As DbParameter
Public Function AssignParameterValues(ByVal strParameterName As String, ByVal strParameterValue As String, ByVal intDatabaseType As Integer) As Integer
Dim intArrayBound As Integer
intArrayBound = UBound(paramValues)
If intArrayBound > 0 Then
ReDim paramValues(intArrayBound)
End If
If intDatabaseType = 1 Then
paramValues(intArrayBound) = New SqlParameter(strParameterName, strParameterValue)
ElseIf intDatabaseType = 2 Then
paramValues(intArrayBound) = New OracleParameter(strParameterName, strParameterValue)
'paramValues(intArrayBound) = New OracleParameter(":" & strParameterName, OracleType.Int32)
'paramValues(intArrayBound).Value = strParameterValue
End If
Return intArrayBound
End Function
Public Function getParameterValues() As DbParameter()
Return paramValues
End Function
Public Sub Dispose() Implements IDisposable.Dispose
Erase paramValues
paramValues = Nothing
End Sub
End Class
The webpage function looks like this:
Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim objParameterValues As New clsParameterValues
Using objParameterValues
'Use the objParameterValues class here.
End Using
objParameterValues=nothing
End Using
End Sub
I am using IDisposable.Dispose to erase the array before setting it to Nothing. I believe this is bad practice because the Array class does not implement IDisposable. Is it even necessary to erase an array and set it to Nothing? (Does the garbage collector deal with this?)
Public Sub Dispose() Implements IDisposable.Dispose
Erase paramValues
paramValues = Nothing
End Sub
The Erase statement dates from old versions of Basic, the kind where manual memory management was useful. No more, memory management is automatic in .NET. It is still supported for compatibility reasons. All it does is set the array reference to Nothing. So your code is equivalent to:
Public Sub Dispose() Implements IDisposable.Dispose
paramValues = Nothing
paramValues = Nothing
End Sub
So no point to it. You should never implement IDisposible to set a variable to Nothing, that's not the interface's contract. A disposed object may never be used again. So no point in setting the array reference to null since that doesn't actually do anything to the real array object on the garbage collected heap. I cannot otherwise see a scenario where you would want to help, any clsParameterValues object should have a limited lifetime. It just isn't useful anymore when you null the array reference.
Just remove the IDisposable implementation.
Is it even necessary to erase an array and set it to nothing?
No. The GC does that in its own time. In fact, I’m not even sure whether Erase actually frees money or whether it simply points the array somewhere else.It just sets the variable to Nothing. Erase probably exists out of compatibility with VB6. C# for instance doesn’t have it (and neither does it have ReDim, although Array.Resize exists of course, albeit with slightly different semantics).
On the other hand, if your array contained IDisposable objects (which it doesn’t) you should dispose those in your Dispose method by iterating over the array and disposing them in turn. But again, the array itself doesn’t need to be erased.
As a general remark, your code reads very much like VB6. Change that. Don’t declare variables without initialising them. Don’t use UBound etc (there’s the .Length property instead). If you find yourself using ReDim very often use a System.Collections.Generic.List instead of an array.
I am new to VB.NET and WPF.
I am building a "Questionnaire" app. Users will be presented sequentially with different questions/tasks (windows). After they respond on each question/task and press a "submit" button a new window will open with a new question/task, and previous window will close. After each question, when the button is pressed, I need to store data to some global object. After all questions are answered the data of this object should be written out to the output file.
I figured out that Dictionary will be the best to store the results after each window.
I am not sure how, where to create this global Dictionary and how to access it. Should I use View Model? If yes, can you give an example? Or, should it be just a simple class with shared property? (something like this)
EDIT 2: I tried many different ways recommended online
GlobalModule:
Module GlobalModule
Public Foo As String
End Module
GlobalVariables:
Public Class GlobalVariables
Public Shared UserName As String = "Tim Johnson"
Public Shared UserAge As Integer = 39
End Class
Global properties:
Public Class Globals
Public Shared Property One As String
Get
Return TryCast(Application.Current.Properties("One"), String)
End Get
Set(ByVal value As String)
Application.Current.Properties("One") = value
End Set
End Property
Public Shared Property Two As Integer
Get
Return Convert.ToInt32(Application.Current.Properties("Two"))
End Get
Set(ByVal value As Integer)
Application.Current.Properties("Two") = value
End Set
End Property
End Class
Here is where I save the data to global variables/properties in the first window. I need to store data in this subroutine before closing an old window and opening a new window. I use MessageBox just for testing.
Private Sub btnEnter_Click(ByVal sender As Object, ByVal e As System.Windows.RoutedEventArgs) Handles btnEnter.Click
Dim instructionWindow As InstructionsWindow
instructionWindow = New InstructionsWindow()
Application.Current.Properties("number") = textBoxValue.Text
Globals.One = "2"
Globals.Two = 3
MessageBox.Show("GlobalVariables: UserName=" & GlobalVariables.UserName & " UserAge=" & GlobalVariables.UserAge)
GlobalVariables.UserName = "Viktor"
GlobalVariables.UserAge = 34
GlobalModule.Foo = "Test Foo"
'testing if it saved tha value
'MessageBox.Show(Application.Current.Properties("number"))
Application.Current.MainWindow.Close()
instructionWindow.ShowDialog()
End Sub
Next subroutine is where I am trying to retrieve the value from global Properties/variables in the second window, but message boxes come out empty. There might also the case that I am assigning values in a wrong way, or not reading them in a right way (casting?) :
Private Sub FlowDocReader_Initialized(ByVal sender As Object, ByVal e As System.EventArgs) Handles FlowDocReader.Initialized
' Get a reference to the Application base class instance.
Dim currentApplication As Application = Application.Current
MessageBox.Show(currentApplication.Properties("number"))
MessageBox.Show("One = " & Globals.One & " Two = " & Globals.Two)
MessageBox.Show("GlobalVariables: UserName=" & GlobalVariables.UserName & " UserAge=" & GlobalVariables.UserAge)
MessageBox.Show("GlobalModule.Foo = " & GlobalModule.Foo)
Dim filename As String = My.Computer.FileSystem.CurrentDirectory & "\instructions.txt"
Dim paragraph As Paragraph = New Paragraph()
paragraph.Inlines.Add(System.IO.File.ReadAllText(filename))
Dim document As FlowDocument = New FlowDocument(paragraph)
FlowDocReader.Document = document
End Sub
Thanks.
You can make public Dictionary property for form and put your dictionry to this property or make constructor with Dictionary argument.
You already have this dictionary Application.Properties
Look here, please.
First, you can define a dictionary (list of lists) as follows at the beginning of a form or in a module
Dim dic As New Dictionary(Of String, List(Of String))
As the user completes questions on a form, write the partucular form number and query results to a single record in the dic before going to the next form (place this code into the "Next" button):
'Assume q1response=3, q2response=4,..., qpresponse="text", etc.
Dim myValues As New List(Of String)
myValues.Add(formname)
myValues.Add(q1response)
myValues.Add(q2response)
.
.
myValues.Add(qpresponse)
dic.Add(username, myValues)
When a user is done, there will be multiple records in the dictionary, each of which starts with their name and is followed by question responses. You can loop through multiple dictionary records, where each record is for a user using the following:
For Each DictionaryEntry In dic 'this loops through dic entries
Dim str As List(Of String) = DictionaryEntry.Value
'here you can do whatever you want with results while you read through dic records
'username will be = str(0)
'formname will be str(1)
'q1 response on "formname" will be str(2)
'q2 response on "formname" will be str(3)
'q3 response on "formname" will be str(4)
...
Next
The trick is that there will be multiple dictionary records with results for one user, where record one can have results like "John Doe,page1,q1,q2,q3" and record 2 will be "John Doe,page2,q4,q5,q6." Specifically, the "str" in the above loop will be an array of string data containing all the items within each dictionary record, that is, in str(0), str(1), str(2),... This is the information you need to work with or move, save, analyze, etc.
You can always put all the code I provided in a class (which will be independent of any form) and dimension the sic is a Sub New in this class, with the updating .Add values lines in their own sub in this same class). Then just Dim Updater As New MyNewClassName. Call the Updater in each continue button using Call Updater.SubNameWithAddValues(q1,q2,...qp). It won't matter where you are in your program since you using a specific class. The one thing I noticed with my code is that you can only use the line that adds the "key" or the username once, so use it after the last query -so put it in a Sub Finished in your new class and call as Call Updater.Finished(username,q30,q31,last)
I followed an example on stackoverflow about how to read database records into variables. This is the first time doing this and I feel that I'm close but I'm baffled at this point about the problem.
Here is the link I am referring to:
Visual Basic 2010 DataSet
My code is shown below.
Public Class Form1
' DataSet/DataTable variables
Dim testdataDataSet As New DataSet
Dim dttestdataDataTable As New DataTable
Dim datestdataDataAdapter As New Odbc.OdbcDataAdapter
' Variables for retrieved data
' Dim sSpeed As String = ""
' Dim sFuelprice As String = ""
Dim sSpeed As Integer
Dim sFuelprice As Integer
'Connect to the database
''
'Fill DataSet and assign to DataTable
datestdataDataAdapter.Fill(TestdataDataSet , "TestdataDataSet")
dttestdataDataTable = TestdataDataSet.Tables(0)
'Extract data from DataTable
' Rows is the row of the datatable, item is the column
sSpeed = dtTestdataDataTable.Rows(0).Item(0).ToString
sFuelprice = dtTestdataDataTable.Rows(0).Item(1).ToString
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
result.Text = Val(miles.Text) * sSpeed * sFuelprice
End Sub
End Class
Basically, I am getting declaration errors and I don't understand why since the example I was following clearly declared them. I'm connecting to an Access DB called "testdata.mdb" which contains only 1 record with two fields that I want to use throughout the program. The exanple said to dim the variables for each field as strings but this created more dim errors so I made them into integers and remarked out the original dim statements in the meantime (since they're going to be used in calculations.) The dataadapter and datatable variables also are getting flagged for not being declared when they were earlier in the program. I know this must be a simple thing to fix but I'm just not seeing it.
The form is just a simple thing where the user types in a number and a result is produced by using the numbers read in from the database. In short, I want to be able to do simple calculations with a database within a program and the dim statement thing is getting in the way.
If someone can please clarify what I should do, that would be very much appreciated. Thanks!
When you're trying to learn new technology, it's usually best to work from the outside in. The "outside-most" object in your case seems to be an OdbcConnection object.
Public Class Form1
Const connectionString as String = "Driver={Microsoft Access Driver (*.mdb)};DBQ=c:\bin\Northwind.mdb"
Dim connection As New OdbcConnection(connectionString)
connection.Open()
connection.Close()
end Class
Resolve errors at that level first. Then add a declaration for the data adapter--only for the data adapter--and resolve any errors with that. Repeat until you finish your class.
See OdbcConnectionString, and refer to the connection string web site if you need to.
I apologize for the delay in writing the answer to close off this question and sum it up.
In my case, it dataset is a one row database called testdata and contains 20 fields.
The solution that worked is as follows:
Immediately after the form1_load event, the variables can be immediately written after the dataadapter line:
Me.TestdataTableAdapter.Fill(Me.fooDataSet.testdata)
speed = Me.fooDataSet.testdata(0).speed
fuelprice = Me.fooDataSet.testdata(0).fuelprice
mpg = Me.fooDataSet.testdata(0).mpg
Then just DIM the variables to whatever you want them to be (in this case, speed is an integer, fuelprice is a decimal and MPG is a decimal) right after the PUBLIC CLASS statement at the top of your form's code.
You can then manipulate the variables in calculations after a button click as such:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
fuelcost = CDec((miles.Text/ mpg) * fuelprice)
txtfuelcost.Text = fuelcost.ToString
End Sub
Thank you all for your responses!