Public Function MethodOne(ByVal s As String) As String
Dim sb As New StringBuilder()
sb.Append(s)
sb.Append(MethodTwo())
return sb.ToString()
End Function
Public Function MethodTwo() As String
Dim i As Integer = 0
For index As Integer = 0 To 5
i = index
Next
return i.ToString()
End Function
I want to retain the value of i, but once it goes back into MethodOne, it loses its value. I tried making it static i As integer = 0, but this did not work.
sorry misread that. How about creating a property called Count, and update it whenever MethodTwo is called. You can use the Property Count in MethodTwo instead of i.
Public Function MethodOne(ByVal s As String) As String
Dim sb As New StringBuilder()
sb.Append(s)
sb.Append(MethodTwo())
return sb.ToString()
End Function
Public Property Count As Integer
'Count will be zero when initialized
Public Function MethodTwo() As String
'Dim i As Integer = 0
For index As Integer = 0 To 5
Count = Count + index
Next
return Count.ToString()
End Function
Consider this example which is a bit different than yours (adds 5 to i instead of setting a value of 5)
Public Function MethodOne(ByVal s As String) As String
Dim sb As New StringBuilder()
sb.Append(s)
sb.Append(MethodTwo())
return sb.ToString()
End Function
Public Function MethodTwo() As String
Static i As Integer = 0
i+=5
return i.ToString()
End Function
Now, on the first run i will be set to its static value, which is 0. It will be incremented by 5, so the value will be 5. On the second one, the value of i is still 5, and it will be incremented by 5. The new value will be 10.
In your example, i was always set to 5, so it didn't change anything if you retained the value or not.
Edit after question changed:
What you want to do is have a class member, not a method variable. If the value is still 0 once the method has run, then there are two possible reasons for this. Either:
The variable is never set (AgeQualifyingCode is never 8 or 10)
The variable is set to 0 inside the method.
You can find out what is happening with some debugging with breakpoints.
Related
I've got a question about using two-dimensional array.
Public twolist(,) As String
For i As Integer = 0 To twolist.length()-1
If Func(twolist(i, )) Then 'this part is hard for me
'doing something
End If
Public Function Func(ByVal CancelInput() As String) As Boolean
What i want to do is Passing two-dimensional array to an array.
I want to read one row in two-dimensional array and pass to function(Func), which is using an array.
Hope You can understand my question... and Thank you!
As an alternative to the For Next Loop, you could use Linq (if you are confortable with it) to perform the same task.
This transforms each element of the source array to a String, groups them in an IEnumerable(Of String) and the result is converted to an unidimensional Array of Strings:
Dim twolist(N, N) As String
Dim CancelInput() As String = twolist.Cast(Of String).Select(Function(str) str).ToArray()
Dim result As Boolean = Func(CancelInput)
I have just used an arbitrary size for your array. You need nested For loops to iterate through a 2 dimensional array. The outer loop goes through the rows and the inner loop adds the value in each field to another array that you are passing to your Function. Each row is passed individually as a single dimension array.
Private Sub TwoDimensionalArray()
Dim twolist(,) As String
ReDim twolist(10, 5)
'First you will need to add data to your array
For x As Integer = 0 To 10
Dim arrayRow(5) As String
For y As Integer = 0 To 5
arrayRow(y) = twolist(x, y)
Next
If Func(arrayRow) Then 'this part is hard for me
'doing something
End If
Next
End Sub
Public Function Func(ByVal CancelInput() As String) As Boolean
Return True
End Function
Mary's answer is good, but assumes you know the length of each dimension.
I have changed it slightly to use the Array.GetLength function:
Private Sub TwoDimensionalArray()
Dim twolist(,) As String
ReDim twolist(10, 5)
'First you will need to add data to your array
For x As Integer = 0 To 10
'Fetch the length of this dimension:
Dim i As Integer = twolist.GetLength(x)
Dim arrayRow(i) As String
For y As Integer = 0 To i - 1
arrayRow(y) = twolist(x, y)
Next
If Func(arrayRow) Then
'do something
End If
Next
End Sub
Public Function Func(ByVal CancelInput() As String) As Boolean
Return True
End Function
Note:
In VB.Net, ReDim twoList(10,5) actually gives you an array of (11,6).
Array.GetLength(0) will return 6 (0,1,2,3,4,5).
In short, Dim specifies the maximum index in each dimension, Length & GetLength return the count of elements.
While CommitReader.Read()
Yield New Commit() With {
.FirstValue = CommitReader.GetInt32(CommitReader.GetOrdinal("FirstValue")),
.SecondValue = CommitReader.GetString(CommitReader.GetOrdinal("SecondValue")).Trim(),
'Lots of values
End While
I know I can do something like this; however there are 24 properties and I would like to make this part as clean as possible
While CommitReader.Read()
new Commit (){
Dim index As Integer = reader.GetOrdinal("FirstValue")
If reader.IsDBNull(index) Then
FirstValue = String.Empty
Else
FirstValue = reader(index)
End If
index = reader.GetOrdinal("SecondValue")
If reader.IsDBNull(index) Then
SecondValue = String.Empty
Else
SecondValue = reader(index)
End If
}
End While
Is there a better way to handle this type of thing? I am mainly a C# developer so if the syntax is off a little sorry, I am winging it in VB.
It's a shame that SqlDataReader doesn't have the generic Field extension method like DataRow does, but you could define your own extension method (has to be in a module in VB.NET) to help with the null checks, perhaps something like this:
<Extension>
Function GetValue(Of T)(rdr As SqlDataReader, i As Integer) As T
If rdr.IsDBNull(i) Then
Return Nothing
End If
Return DirectCast(rdr.GetValue(i), T)
End Function
And use it something like this:
While CommitReader.Read()
Yield New Commit() With {
.FirstValue = CommitReader.GetValue(Of Integer?)(CommitReader.GetOrdinal("FirstValue")),
.SecondValue = CommitReader.GetValue(Of String)(CommitReader.GetOrdinal("SecondValue")),
'Lots of values
End While
I haven't tested this fully to make sure it handles all data types appropriately (may be worth looking at DataRowExtensions.Field to see how it does it).
Note that you are using String.Empty as the "null" value for strings, while this will use Nothing/null (I also had to remove the .Trim call to avoid NREs). If you want empty string instead, you could use (adding the Trim back in):
.SecondValue = If(CommitReader.GetValue(Of String)(CommitReader.GetOrdinal("SecondValue")), String.Empty).Trim()
You may also want to move the GetOrdinal calls out of the loop to improve performance.
Obviously you have repetition in your code if ... else ... condition.
So you can extract it in another method.
For your case generic extension method seems good candidate.
Public Module Extensions
<Extension>
Public Function GetValueOrDefault(Of T)(originalValue As object,
defaultValue As T) As T
If originalValue = DbNull.Value Then
Return defaultValue
End If
return DirectCast(originalValue, T)
End Function
End Module
Then use it:
While CommitReader.Read() = True
Dim temp = new Commit With
{
Dim index As Integer = reader.GetOrdinal("FirstValue")
FirstValue = reader(index).GetValueOrDefault(String.Empty)
Dim index As Integer = reader.GetOrdinal("SecondValue")
FirstValue = reader(index).GetValueOrDefault(String.Empty)
}
End While
You can create another overload which return "default" value for given type if it is DbNull
<Extension>
Public Function GetValueOrDefault(Of T)(originalValue As object) As T
Return originalValue.GetValueOrDefault(Nothing)
End Function
Nothing in vb.net is default value, for reference types it is null for Integer it is 0 for example.
For using this overload you need provide type parameter explicitly
While CommitReader.Read() = True
Dim temp = new Commit With
{
Dim index As Integer = reader.GetOrdinal("FirstValue")
FirstValue = reader(index).GetValueOrDefault(Of String)()
Dim index As Integer = reader.GetOrdinal("SecondValue")
FirstValue = reader(index).GetValueOrDefault(Of String)()
}
End While
Notice that your solution executing reader twice, for checking is it null and for reading value. This can cause "tiny" performance issue.
So in extension method above we read value only once and then check value for DbNull.
If you concatenate a string with a Null you get the string:
FirstValue = reader(index) & ""
Kind of "unprofessional" but saves a lot of coding time if all you are doing is converting a possible Null to an empty string. Easy to forget however, so later data dependent errors may pop up.
When I get to the Read loop I get an index out of bounds error. I think its on the reader ordinal value, but I am not sure why I am getting it.
Private Function Create(Reader As SqlDataReader) As IEnumerable(Of MyObject)
SetOrdinals(MyObjectReader)
Dim MyObjects = New List(Of MyObject)
While MyObjectReader.Read()
Dim Temp = New MyObject() With {
.FirstValue = MyObjectReader.GetValue(Of Integer)(MyObjectReader(FirstValue_Ord)),
.SecondValue = If(MyObjectReader.GetValue(Of String)(MyObjectReader(SecondValue_Ord)), String.Empty).Trim(),
.ThirdValue = If(MyObjectReader.GetValue(Of String)(MyObjectReader(ThirdValue_Ord)), String.Empty).Trim(),
MyObjects.Add(Temp)
End While
Return MyObjects
End Function
Private Sub SetOrdinals(MyObjectReader As SqlDataReader)
FirstValueOrd = MyObjectReader.GetOrdinal("FirstValue")
SecondValue_Ord = MyObjectReader.GetOrdinal("SecondValue")
ThirdValue_Ord = MyObjectReader.GetOrdinal("ThirdValue")
End Sub
End Class
Public Module Extensions
<Extension>
Function GetValue(Of T)(rdr As SqlDataReader, i As Integer) As T
If rdr.IsDBNull(i) Then
Return Nothing
End If
Return DirectCast(rdr.GetValue(i), T)
End Function
End Module
You should just be passing in the ordinal to the GetValue calls:
While MyObjectReader.Read()
Dim Temp = New MyObject() With {
.FirstValue = MyObjectReader.GetValue(Of Integer)(FirstValue_Ord),
.SecondValue = If(MyObjectReader.GetValue(Of String)(SecondValue_Ord), String.Empty).Trim(),
.ThirdValue = If(MyObjectReader.GetValue(Of String)(ThirdValue_Ord), String.Empty).Trim()
}
MyObjects.Add(Temp)
End While
Here my version :)
Private Function Create(reader As SqlDataReader) As IEnumerable(Of MyObject)
Dim objects As New List(Of MyObject)()
Dim ordinals As New Ordinals(reader)
While reader.Read()
Dim Temp As New MyObject With
{
.FirstValue = reader.GetValueOrDefault(Of Integer)(ordinals.FirstValue),
.SecondValue = reader.GetValueOrDefault(ordinals.SecondValue, "").Trim(),
.ThirdValue = reader.GetValueOrDefault(ordinals.ThirdValue, "").Trim()
}
objects.Add(Temp)
End While
Return MyObjects
End Function
Private Class Ordinals
Public Property FirstValue As Integer
Public Property SecondValue As Integer
Public Property ThirdValue As Integer
Public Sub New(reader As SqlDataReader)
FirstValue = reader.GetOrdinal(nameOf(FirstValue))
SecondValue = reader.GetOrdinal(nameOf(SecondValue))
ThirdValue = reader.GetOrdinal(nameOf(ThirdValue))
End Sub
End Class
Public Module Extensions
<Extension>
Function GetValueOrDefault(Of T)(reader As SqlDataReader, ordinal As Integer) As T
Return reader.GetValueOrDefault(Of T)(ordinal, Nothing)
End Function
<Extension>
Function GetValueOrDefault(Of T)(reader As SqlDataReader,
ordinal As Integer,
defaultValue As T) As T
Dim value = reader(ordinal)
If value = DbNull.Value Then
Return defaultValue
End If
Return DirectCast(value, T)
End Function
End Module
Because extension method execute checking for DbNull.Value against already extracted object, we get rid from reading same value twice from SqlDataReader.
SqlDataReader.IsDbNull(index) reads value before checking for DbNull.
Extension method have two overloads:
- One which return default value of given type, if value is DbNull.Value. Nothing in vb.net is default value of type.
- And one which takes parameter for default value you want return if value is DbNull.Value. Possibility pass default value makes lines where you create new object shorter and more readable. We get rid of inline if statement.
Your extension method with name GetValue have "side effects". By name consumer of this method expect to get value from SqlDataReader. So he can expect to get DbNull.Value if database query return NULL, but instead he get null for string or 0 for integer. Name GetValueOrDefault is little bid more informative, so you don't need to go inside method to check what is doing.
I'm having an issue in VBA where every item in the array is being replaced every time i add something to that array.
I am attempting to go through the rows in a given range and cast every row of that into a custom class (named 'CustomRow' in below example). there is also a manager class (called 'CustomRow_Manager' below) which contains an array of rows and has a function to add new rows.
When the first row is added it works fine:
https://drive.google.com/file/d/0B6b_N7sDgjmvTmx4NDN3cmtYeGs/view?usp=sharing
however when it loops around to the second row it replaces the contents of the first row as well as add a second entry:
https://drive.google.com/file/d/0B6b_N7sDgjmvNXNLM3FCNUR0VHc/view?usp=sharing
Any ideas on how this can be solved?
I've created a bit of code which shows the issue, watch the 'rowArray' variable in the 'CustomRow_Manager' class
Macro file
https://drive.google.com/file/d/0B6b_N7sDgjmvUXYwNG5YdkoySHc/view?usp=sharing
otherwise code is below:
Data
A B C
1 X1 X2 X3
2 xx11 xx12 xx13
3 xx21 xx22 xx23
4 xx31 xx32 xx33
Module "Module1"
Public Sub Start()
Dim cusRng As Range, row As Range
Set cusRng = Range("A1:C4")
Dim manager As New CustomRow_Manager
Dim index As Integer
index = 0
For Each row In cusRng.Rows
Dim cusR As New CustomRow
Call cusR.SetData(row, index)
Call manager.AddRow(cusR)
index = index + 1
Next row
End Sub
Class module "CustomRow"
Dim iOne As String
Dim itwo As String
Dim ithree As String
Dim irowNum As Integer
Public Property Get One() As String
One = iOne
End Property
Public Property Let One(Value As String)
iOne = Value
End Property
Public Property Get Two() As String
Two = itwo
End Property
Public Property Let Two(Value As String)
itwo = Value
End Property
Public Property Get Three() As String
Three = ithree
End Property
Public Property Let Three(Value As String)
ithree = Value
End Property
Public Property Get RowNum() As Integer
RowNum = irowNum
End Property
Public Property Let RowNum(Value As Integer)
irowNum = Value
End Property
Public Function SetData(row As Range, i As Integer)
One = row.Cells(1, 1).Text
Two = row.Cells(1, 2).Text
Three = row.Cells(1, 3).Text
RowNum = i
End Function
Class module "CustomRow_Manager"
Dim rowArray(4) As New CustomRow
Dim totalRow As Integer
Public Function AddRow(r As CustomRow)
Set rowArray(totalRow) = r
If totalRow > 1 Then
MsgBox rowArray(totalRow).One & rowArray(totalRow - 1).One
End If
totalRow = totalRow + 1
End Function
Your issue is using
Dim cusR As New CustomRow
inside the For loop. This line is actually only executed once (note that when you single F8 step through the code it does not stop on that line)
Each itteration of the For loop uses the same instance of cusR. Therefore all instances of manager added to the class point to the same cusR
Replace this
For Each row In cusRng.Rows
Dim cusR As New CustomRow
with this
Dim cusR As CustomRow
For Each row In cusRng.Rows
Set cusR = New CustomRow
This explicitly instantiates a new instance of the class
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)