A very simple issue im having trying to return a dataset from a VB.NET object function.
The following shows my function that is currently exiting from the function as soon as the SQL query is run and just before the new object connection is created.
The edit form is called here:
edit.Show()
Within the edit form, the following is run to to retrieve the details of the selected data in the database fro a retrieved datatset of the 'editEntry' method based on the ID set at the constructor.
Private Sub edit_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim editDetails As New DBHandler(ID)
Dim returnedDetails As New DataSet
returnedDetails = editDetails.editEntry()
Dim nameReturned As Object = returnedDetails.Tables("editedTable").Rows(0)(1)
Dim firstNameEdit As String = nameReturned.ToString()
TextBox1.Text = firstNameEdit
This is the function where the problem is occuring. Nothing is being returned from the query
Constructor where the ID is set:
Public Sub New(ByVal ID As Integer)
IDofFault = ID
End Sub
The function of the class:
Public Function editEntry() As DataSet
Dim editDataSet As New DataSet
Dim editSql As String = "SELECT * FROM duraGadget WHERE _id = " + IDofFault + ""
'Exiting from the function here
Dim connectionEdit As New OleDbConnection(conString)
Dim editAdapter As New OleDbDataAdapter(editSql, connectionEdit)
connectionEdit.Open()
editAdapter.Fill(editDataSet, "editedTable")
connectionEdit.Close()
Return editDataSet
End Function
There is no error it simply exits from the function and im not sure why.
You could be receiving an exception and your visual studio debug settings are not configured to stop you on those types of exceptions.
Wrap the contents of the EditEntry function in a Try / Catch block, and put a break point inside the catch. See if that triggers and look at the exception details for more info on what occurred.
Very silly error this was guys. I simply stored the ID value as a sting...then tried to pass it as an Integer to the constructor...the result?.....Conversion exception.
Related
Problem: I am refactoring vb.net code to make it more unit test friendly. I have a vb.net function which has 2 data components. In the original code, both data models were implemented in the code which made it almost impossible to pass test data. I implemented an interface for the first data object which is now injected into the call to the function. This solves the issue of passing mock data to the function when testing. The second data component is executed iteratively inside the function.
Question - Is there a way to "mock" the iterative data retrieval while still maintaining the code functionality?
Basic Function - The data object injected at call time is used to pass parameters to the second database call within the code. This is repeated for each row in the injected DataTable object.
Function Signature: date and dailyScores are injected for Unit Tests or Run Time Execution
Public Shared Function CalcDailyScoresByDate(ByVal dayUtc As Date,
ByVal ReID As Integer,
ByVal dailyScores As DataTable
) As DailyDataCollection
Function Code:
Public Shared Function CalcDailyScoresByDate(ByVal dayUtc As Date,
ByVal ReID As Integer,
ByVal dailyScores As DataTable
) As DailyDataCollection
Dim timeUtc As Date = dayUtc
Dim srvSet As ServiceSettings = New ServiceSettings(dayUtc)
Dim ept As Date = TimeZoneInfo.ConvertTimeFromUtc(timeUtc, TimeZoneInfo.Local)
ept = ept.AddDays(1)
Dim effDayUtc As Date = TimeZoneInfo.ConvertTimeToUtc(ept)
Dim daily As New DailyDataCollection
Try
#Region "Region DataAccess"
Dim regDs = New DataAccess
Try
regDs.InitializeFromMDB(srvSet.MyConnectionString, "MyDb")
Catch ex As Exception
MyUtil.ErrorLog("RegDS.InitializeFromMDB " & ex.Message)
End Try
For Each rw In dailyScores.Rows
Dim drw As New DailyData
drw.ReID = rw(0)
drw.SignalID = rw(1)
drw.MyDay = effDayUtc
drw.dailyScore = rw(2)
' Calls the actual implementation to retrieve the supporting data for each record in the outer for loop
' Need to find a way to allow this to be Unit Tested with Mock data
Dim rsc = regDs.GetRegResource(drw.ReID, drw.SignalID, effDayUtc)
If rsc.Type = DataAccess.ReTypes.DG Then
For Each child In rsc.Children
Dim childDaily As New DailyData
childDaily.ReID = child.ID
childDaily.SignalID = child.SignalID
childDaily.myDay = effDayUtc
childDaily.dailyScore = drw.dailyScore
daily.Add(childDaily)
Next
End If
Next
dailyScores.Dispose()
dailyScores = Nothing
srvSet = Nothing
#End Region
Catch ex As Exception
MyUtil.ErrorLog("CalcDailyScoresByDate: " & ex.Message)
End Try
Return daily
End Function
Beginner here
I have the following code which I would like to call using a button called findCustomerBTN
Public Function Execute(ByVal sqlQuery As String) As ADODB.Recordset
If SecuritySSPIchkbx.Checked Then
chk = "TRUE"
Else chk = "FALSE"
End If
builder.DataSource = ServerBox.Text
builder.InitialCatalog = DatabaseBox.Text
builder.UserID = Username.Text
builder.Password = Password.Text
builder.IntegratedSecurity = chk
MessageBox.Show(builder.ConnectionString)
Using sqlConnection1 As New SqlConnection(builder.ConnectionString)
sqlConnection1.Open()
Try
command = New SqlCommand(sqlQuery, sqlConnection1)
adapter.SelectCommand = command
adapter.Fill(ds, "Create DataView")
adapter.Dispose()
command.Dispose()
sqlConnection1.Close()
dv = ds.Tables(0).DefaultView
DataGridView1.DataSource = dv
Catch ex As Exception
MsgBox(ex.ToString)
End Try
End Using
End Function
How do I call this function:
Private Sub findCustomerBTN_Click(sender As Object, e As EventArgs) Handles
sqlquery = "Select * from customers where name = 'Smith'"
call function?
End Sub
I have googled but I can't wrap my head around how a function works any pointers to help me understand would be great thanks
In VB, a function is a block of code that returns a value. Your code does not return a value, and the type of query execution you're carrying out will never return an ADODB.RecordSet - that's an ancient technology remeniscent of the VB6 era, and you're using a much more modern data access strategy (ADO.NET, DataTables and DataAdapter) though it's not the latest and greatest.
To offer a run through of your code, and the other issues it has:
Execute is a pretty bland name - go for something more specific, just incase you run the wrong execute and some poor prisoner ends up in front of the firing squad
Your function takes an sql string as a parameter to run, but then overwrites it with a fixed string, so there isn't much point offering it as a parameter in the first place. I could call Execute("SELECT * FROM kittens") expecting to get some cute data back, and all I get is the same old customer
Avoid calling MessageBox.Show in any code that shoudl reasonably be expected to run quietly and repeatedly, otherwise the user is going to get hella annoyed. If youre putting this here for debugging purposes, learn how the visual studio debugger works instead
Your code runs an sql query and assigns the resulting data table data to the datasource of a grid, so that the grid will show the data. There's absolutely no need for this code to be a function (and in c# it wouldnt even compile because it doesn't return a value
What are functions? What do they do? They take some inuts and return some outputs:
Public Function AddTheseTwo(a as Integer, b as Integer) As Integer
Return a + b
End Function
They are called like this:
Dim sum = AddTheseTwo(2, 3)
I.e. you give the name of the function and the input values, which can be variables, and store the result (usually, because you want to use it). Here's a code of yours that is a sub - a block of code that doesn't return a value
Private Sub findCustomerBTN_Click(sender As Object, e As EventArgs) Handles
Execute("Select * from customers where name = 'Smith'")
End Sub
It's not linked to your button click, because there's nothing afte rthe Handles keyword. It should be something like Handles findCustomerBTN.Click. You can mash that button all day and nothing will happen
It called Execute but didn't store the return value (because it didn't need to, because Execute doesn't return anything, so Execute should have been declared as a sub, not a function)
Edit:
You mentioned you want the function to return a datatable:
Public Function GetDataTable(ByVal sqlQuery As String) As DataTable 'need to Imports System.Data if you haven't already
If SecuritySSPIchkbx.Checked Then
chk = "TRUE"
Else chk = "FALSE"
End If
'better to declare builder in this function, not elsewhere
builder.DataSource = ServerBox.Text
builder.InitialCatalog = DatabaseBox.Text
builder.UserID = Username.Text
builder.Password = Password.Text
builder.IntegratedSecurity = chk
MessageBox.Show(builder.ConnectionString)
Using sqlConnection1 As New SqlConnection(builder.ConnectionString)
sqlConnection1.Open()
Try
'note: better to declare adapter and command in this function too
command = New SqlCommand(sqlQuery, sqlConnection1)
adapter.SelectCommand = command
Dim dt as New DataTable
adapter.Fill(dt)
adapter.Dispose()
command.Dispose()
sqlConnection1.Close()
Return dt
Catch ex As Exception
MsgBox(ex.ToString)
End Try
End Using
Return Nothing 'a function has to return something from all possible code paths, even if it's Nothing :)
End Function
And then you call it like this, perhaps:
Private Sub findCustomerBTN_Click(sender As Object, e As EventArgs) Handles whateverbutton.Click
'you can set a datatable as a datasource, doesn't have to be the datatable.defaultview
myDataGRidView.DataSource = GetDataTable("Select * from customers where name = 'Smith'")
End Sub
I recommend you turn on the options for Strict/Explicit etc, to encourage better coding practices. By default VB is quite loose, letting you use variables that havent been declared (autodeclaring variable names that are a typo of another variable name etc), automatically returning Nothing for you from functions etc - it's these little auto's that will later lead to bugs and frsutrations. Computer programming si a precise art; turn on all options to force yourself to be as precise as possible
You can call Execute function using this code:
Private Sub findCustomerBTN_Click(sender As Object, e As EventArgs) Handles
Execute("Select * from customers where name = 'Smith'")
End Sub
You also have to remove this line from Execute function:
sqlQuery = ("select * from ac_billbook where ref = '900123'")
Please follow Steve suggestion to read a good book about programming in VB.NET.
I put together this bit of code from a few other samples, and I am getting an error I cant understand. On this line in the code below, on the word Observer,
Dim Results As ManagementObjectCollection = Worker.Get(Observer)
I get the error
"Value of type 'System.Management.ManagementOperationObserver' cannot be converted to 'Integer'"
Can somebody explain what this means?
There are two signatures for ManagementObjectSearcher.Get(), one has no parameters and the other has one parameter, a ManagementOperationObserver for async operation. That is what I am providing, yet the error indicates conversion involving an integer?
Public Shared Sub WMIDriveDetectionASYNC(ByVal args As String())
Dim Observer As New ManagementOperationObserver()
Dim completionHandler As New MyHandler()
AddHandler Observer.Completed, AddressOf completionHandler.Done
Dim Machine = "192.168.0.15"
Dim Scope = New ManagementScope("\\" & Machine & "\root\cimv2")
Dim QueryString = "select Name, Size, FreeSpace from Win32_LogicalDisk where DriveType=3"
Dim Query = New ObjectQuery(QueryString)
Dim Worker = New ManagementObjectSearcher(Scope, Query)
Dim Results As ManagementObjectCollection = Worker.Get(Observer) 'use parameter to make async
For Each item As ManagementObject In Results
Console.WriteLine("{0} {2} {1}", item("Name"), item("FreeSpace"), item("Size"))
Dim FullSpace As Long = (CLng(item("Size")) - CLng(item("FreeSpace"))) \ 1000000
Console.WriteLine(FullSpace)
Next
End Sub
Public Class MyHandler
Private _isComplete As Boolean = False
Public Sub Done(sender As Object, e As CompletedEventArgs)
_isComplete = True
End Sub 'Done
Public ReadOnly Property IsComplete() As Boolean
Get
Return _isComplete
End Get
End Property
End Class
Thanks for any advice!
I think that uses a reference type to get the result and put it in the object you sent as a parameter. So I think it just needs to look like:
Worker.Get(Observer)
instead of trying to set something = to that since it isn't a function that returns a value.
Then use the events you hook up to the object to handle whatever you need to do with the items you find.
I am getting the error "Format Exception was unhandled at "Do While objectReader.Peek <> -1
" and after. any help would be wonderful.
'Date: Class 03/20/2010
'Program Purpose: When code is executed data will be pulled from a text file
'that contains the named storms to find the average number of storms during the time
'period chosen by the user and to find the most active year. between the range of
'years 1990 and 2008
Option Strict On
Public Class frmHurricane
Private _intNumberOfHuricanes As Integer = 5
Public Shared _intSizeOfArray As Integer = 7
Public Shared _strHuricaneList(_intSizeOfArray) As String
Private _strID(_intSizeOfArray) As String
Private _decYears(_intSizeOfArray) As Decimal
Private _decFinal(_intSizeOfArray) As Decimal
Private _intNumber(_intSizeOfArray) As Integer
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
'The frmHurricane load event reads the Hurricane text file and
'fill the combotBox object with the data.
'Initialize an instance of the StreamReader Object and declare variable page 675 on the book
Dim objectReader As IO.StreamReader
Dim strLocationAndNameOfFile As String = "C:\huricanes.txt"
Dim intCount As Integer = 0
Dim intFill As Integer
Dim strFileError As String = "The file is not available. Please restart application when available"
'This is where we code the file if it exist.
If IO.File.Exists(strLocationAndNameOfFile) Then
objectReader = IO.File.OpenText(strLocationAndNameOfFile)
'Read the file line by line until the file is complete
Do While objectReader.Peek <> -1
**_strHuricaneList(intCount) = objectReader.ReadLine()
_strID(intCount) = objectReader.ReadLine()
_decYears(intCount) = Convert.ToDecimal(objectReader.ReadLine())
_intNumber(intCount) = Convert.ToInt32(objectReader.ReadLine())
intCount += 1**
Loop
objectReader.Close()
'With any luck the data will go to the Data Box
For intFill = 0 To (_strID.Length - 1)
Me.cboByYear.Items.Add(_strID(intFill))
Next
Else
MsgBox(strFileError, , "Error")
Me.Close()
End If
End Sub
Put a break-point on these lines and step through your code:
_decYears(intCount) = Convert.ToDecimal(objectReader.ReadLine())
_intNumber(intCount) = Convert.ToInt32(objectReader.ReadLine())
Whatever is being returned by ReadLine isn't in the proper decimal or integer format when passed to the converters. You'll need to add some try/catch blocks around the do-while loop operations to handle it gracefully and make sure your data is formatted the way you expected since the wrong parts are being used in this scenario.
Also, each call to ReadLine is returning an entirely new line and the Peek check won't account for those. As long as you can trust your data that's fine.
Instead of using Convert.ToDecimal an Convert.ToInt32, try using Decimal.TryParse() and Int32.TryParse(). If they don't parse, you know your file isn't setup correctly. If they do parse, then you've loaded the value into a variable for your use.
EDIT:
Use it like this.
Dim myDecimal As Decimal
If Decimal.TryParse(objectReader.ReadLine(), myDecimal) Then
'your string successfully parsed. Use myDecimal however you want. It has the parsed value.
Else
'your string is not a decimal. Now that you know that, you can handle this situation here without having to catch an exception.
End If
Sorry, that's the best subject I can come up with, if I understood the solution better, I could probably phrase a better subject line.
I am using a great grid control, Super List,l located here:
http://www.codeproject.com/KB/list/outlooklistcontrol.aspx?fid=449232&df=90&mpp=25&noise=3&sort=Position&view=Quick&fr=276
Before you read the problem, please note that you can download a very small VB.NET 2005 sample app which demos the problem:
http://dokmanovich.com/Documents/SuperListEvents.zip
Getting the answer to my question will, I hope, help me to understand dynamic events better in the context of what I am trying to accomplish.
The grid works like this: When you add a column to the grid, you specify the address of an event handler which will return the value at run time. In this case, the CC_ItemValueAccessor function. The latter function will be called with an input parameter which, in this case, is a "ToDo" object. Each ToDo object will be rendered as one row in the grid. The job of the CC_ItemValueAccessor function is to return the column value to be displayed by the grid for the row that corresponds to the passed-in ToDo object.
This works fine till I take it to the next step:
I want to dynamically create columns at run time. For example, I want to display the output of a datatable returned as a result of executing a user-specified SQL.
Using the earlier described static approach, I have one columnItemValueAccessor function responsible for returning the value of each column in the grid for the passed in row object. Now, since the columns are determined at run time based on the SQL returned results, I believe I need to write a generic handler that handles all columns, determines the name of the column that triggered this event and then returns the value for that column within the row object that is passed in as the sole parameter.
The problem is that the ItemValueAccessor function has a signature that only includes the row object and I do not know of a way to determine which column name is needed since all of the columns were hooked up to the same ItemValueAccessor function as the event handler.
I suspect that this is just a limitation of the control and that to overcome this problem I would have to enhance the underlying custom control, but that is likely beyond my current skills as it is an advanced control written in C# and I am a VB guy.
Here's the code:
Private Sub AddCcColumn()
Dim NewColumn As New BinaryComponents.SuperList.Column("CC", "CC", 110, AddressOf Cc_ItemValueAccessor)
_SuperList.Columns.Add(NewColumn)
End Sub
Private Function Cc_ItemValueAccessor(ByVal rowItem As Object) As Object
Dim ToDo As ToDo = CType(rowItem, SrToDoAndException).ToDo
Return ToDo.CCs.ToString
End Function
'---------------------------
And here are the signatures of the Column's instantiator method and the definition of the last parameter which is responsible for specifying the procedure that handles identifies the event handler responsible for returning the value of the column.
Public Sub New(ByVal name As String, ByVal caption As String, ByVal width As Integer, ByVal columnItemValueAccessor As BinaryComponents.SuperList.ColumnItemValueAccessor)
Member of BinaryComponents.SuperList.Column
Public Sub New(ByVal object As Object, ByVal method As System.IntPtr)
Member of BinaryComponents.SuperList.ColumnItemValueAccessor
Does anyone have any suggestions or am I stuck? I would really love to utilize the fantasic grouping capabilities of this control so I can display dynamic output that allows the user to group the dynamic output of a SQL by any column that they want.
I addressed the question to the author at the above site but it has gone unanswered. This is a desperate attempt to find a way to do this.
Thanks for bearing with me. I hope this question isn't rejected based on the fact that I refer to a third party control. My hope is that the answer lies in a better understanding of delegates, a more universal topic.
I used a lambda function, as Matthew suggested. Here is the code from the dynamic approach:
Private Sub btnDynamic_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDynamic.Click
ListControl1.Columns.Clear()
For Each DataCol As DataColumn In _ds.dtbPerson.Columns
' Get the column name in a loop variable - it needs to be in loop scope or this won\'t work properly'
Dim colName = DataCol.ColumnName
' Create the function that will be called by the grid'
Dim colLambda As ColumnItemValueAccessor = Function(rowItem As Object) General_ItemValueAccessor(rowItem, colName)
' Setup each column in the grid'
Dim NewColumn As New BinaryComponents.SuperList.Column(DataCol.ColumnName, DataCol.ColumnName, 220, colLambda)
ListControl1.Columns.Add(NewColumn)
Next
End Sub
Private Function General_ItemValueAccessor(ByVal rowItem As Object, ByVal colName As Object) As Object
Dim rowPerson As DataRow = CType(rowItem, DataRow)
Return rowPerson.Item(colName).ToString
End Function
Here's a quick primer on how it works:
Each time through the loop the lambda function is creating a new callback function for each column that looks something like this:
Class Func1
Dim colName1 As String = "PersonId"
Private Function General_ItemValueAccessor1(ByVal rowItem As Object) As Object
Dim rowPerson As DataRow = CType(rowItem, DataRow)
Return rowPerson.Item(Me.colName1).ToString
End Function
End Class
Class Func2
Dim colName2 As String = "LastName"
Private Function General_ItemValueAccessor2(ByVal rowItem As Object) As Object
Dim rowPerson As DataRow = CType(rowItem, DataRow)
Return rowPerson.Item(Me.colName2).ToString
End Function
End Class
... for however many columns you have - 3 in this case.
You need the colName variable within the loop and not use just DataCol.ColumnName directly in the lambda. Otherwise, when the grid gets around to calling the callback functions, that DataCol variable would be equal to the last value from the collection (or Nothing) for all the callback functions.
Basically, it would do this and you wouldn't get what you expected:
Class Func
Dim DataCol1 = DataCol
Private Function General_ItemValueAccessor1(ByVal rowItem As Object) As Object
Dim rowPerson As DataRow = CType(rowItem, DataRow)
Return rowPerson.Item(Me.DataCol1.ColumnName).ToString
End Function
Private Function General_ItemValueAccessor2(ByVal rowItem As Object) As Object
Dim rowPerson As DataRow = CType(rowItem, DataRow)
Return rowPerson.Item(Me.DataCol1.ColumnName).ToString
End Function
...
End Class
Hope that helps. Good luck.
The problem is that the ItemValueAccessor function has a signature that only includes the row object and I do not know of a way to determine which column name is needed since all of the columns were hooked up to the same ItemValueAccessor function as the event handler.
Okay, I haven't used that control in the past, and I'm really a C# person. But I think you may be able to accomplish this by creating a new lambda function for each column. Something like:
Private Sub AddCcColumn(ByVal sender As System.Object As System.String)
colLambda = (Function(rowItem As Object) Cc_InternalItemValueAccessor(columnName, rowItem))
Dim NewColumn As New BinaryComponents.SuperList.Column("CC", "CC", 110, colLambda)
_SuperList.Columns.Add(NewColumn)
End Sub
Then, colLambda will fit the signature, while your internal Cc_InternalItemValueAccessor gets the info it needs. Totally untested, but I think the basic idea works.