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« on: January 30, 2018, 04:11:54 PM »
Good afternoon all,
I have a question regarding event arguments and their correct use.
I have an app that I have created several different EventArgs for different events. Each passing the needed information to the event sub.
The class this sub is located in is declared once from the MainForm. In this sub, I am using StatusArgs as my event argument.
My question is, is it necessary for me to be calling "New StatusArgs" every time I raise an event? Would calling "New StatusArgs" be creating a new instance that eventually uses up resources?
I suppose the real question is, after calling "New StatusArgs" and setting the information in it, does the instance hang out forever in memory?
Would the better option be to create one instance of StatusArgs for the class, and then just set the arguments every time I raise the event? Would doing this essentially overwrite the variables that are stored in the instance?
Public Sub VerifyPart(ByVal scan As String)
Dim partFound As Boolean = False
For Each item As ListViewItem In _list.Items
If scan = item.SubItems.Item(1).Text Then
If CheckOffItem(item) = True Then
RaiseEvent OnPartProcessed(Me, New StatusArgs(0, String.Format("Part# {0} is valid! Please scan the next part.", scan), Color.Green, Color.White))
_audio.ValidScan()
Else
RaiseEvent OnPartProcessed(Me, New StatusArgs(2, String.Format("Part# {0} previously scanned!" & vbNewLine & "Verify your quanity and try again.", scan), Color.Red, Color.White))
_audio.InvalidScan()
End If
partFound = True
End If
Next item
If partFound = False Then
If scan = "NoRead" Then
RaiseEvent OnPartProcessed(Me, New StatusArgs(2, "Scanner did not find a bar code. Try again.", Color.Red, Color.White))
RaiseEvent InvalidLog(Me, New StatusArgs(scan, "Scanner did not find a bar code. No Read."))
Else
RaiseEvent OnPartProcessed(Me, New StatusArgs(2, String.Format("Part# {0} is invalid. Please verify your parts.", scan), Color.Red, Color.White))
RaiseEvent InvalidLog(Me, New StatusArgs(scan, String.Format("Part# {0} was not found in the current parts list.", scan)))
_audio.InvalidScan()
End If
End If
End Sub
''' <summary>
''' Station Status Arguments Class For Passing Information To The Status Panel.
''' </summary>
Public Class StatusArgs
Inherits EventArgs
Private _code As Integer
Private _msg As String
Private _scan As String
Private _backclr As Color
Private _foreclr As Color
''' <summary>
''' Creates a new instance to pass status arguments to the status panel.
''' </summary>
''' <param name="code">Determines what the graphic and color is set to. 0=No Change To Image 1=Scanning Complete 2=Scan Invalid 3=General Alarm 4=Ready</param>
''' <param name="msg">Text to set the status to.</param>
''' <param name="backclr">Specify what color to set backcolor on status panel.</param>
''' <param name="foreclr">Specify what color to set the text to.</param>
Public Sub New(ByVal code As Integer, ByVal msg As String, ByVal backclr As Color, ByVal foreclr As Color)
_code = code
_msg = msg
_backclr = backclr
_foreclr = foreclr
End Sub
''' <summary>
''' Creates new instance of StatusArgs to pass scanned code and message.
''' </summary>
''' <param name="scan">The scanned bar code to pass.</param>
''' <param name="msg">The message to attach.</param>
Public Sub New(ByVal scan As String, ByVal msg As String)
_scan = scan
_msg = msg
End Sub
''' <summary>
''' Indicates what status image/color should be displayed.
''' </summary>
''' <returns>Integer</returns>
Public ReadOnly Property Code As Integer
Get
Return _code
End Get
End Property
''' <summary>
''' Gets the status message.
''' </summary>
''' <returns>String</returns>
Public ReadOnly Property Message As String
Get
Return _msg
End Get
End Property
''' <summary>
''' Gets the scanned code associated with this event.
''' </summary>
''' <returns>String</returns>
Public ReadOnly Property Scan As String
Get
Return _scan
End Get
End Property
''' <summary>
''' Gets the image that the status image should be set to.
''' </summary>
''' <returns>Image</returns>
Public ReadOnly Property Image As Image
Get
Select Case _code
Case 0
Return Nothing
Case 1 'scanning complete
Return My.Resources.greenCheck
Case 2 'invalid scan
Return My.Resources.traffic_light_red
Case 3
Return My.Resources.important
Case 4 'station ready
Return My.Resources.traffic_light_green
Case Else
Return My.Resources.gear
End Select
End Get
End Property
''' <summary>
''' Gets the back color of the status image and message.
''' </summary>
''' <returns>Color</returns>
Public ReadOnly Property BackColor As Color
Get
Return _backclr
End Get
End Property
''' <summary>
''' Gets the fore ground color for the status message.
''' </summary>
''' <returns>Color</returns>
Public ReadOnly Property ForeColor As Color
Get
Return _foreclr
End Get
End Property
End Class
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