VB.NET中如何提取生产单元首尾时间戳计算耗时？

Great question! Instead of trying to extract timestamps from the ListBox items later (which would require re-parsing strings unnecessarily), the most efficient approach is to track the first and last timestamps as you read the file. Here's how to implement this in your existing code:

Step 1: Add Variables to Track Timestamps #

First, declare nullable DateTime variables at the class level to hold the first and last times for each production cell. Nullable types let us check if we've received any records yet:

Private firstTimeCell1 As DateTime?
Private lastTimeCell1 As DateTime?
Private firstTimeCell2 As DateTime?
Private lastTimeCell2 As DateTime?

Step 2: Modify File Reading Logic to Parse Timestamps #

Instead of relying on String.Contains to check for cell names and colors, split each line into its components using the comma separator. This makes parsing the timestamp and color number much more reliable:

In your btnBrowse_Click method, replace the inner loop with this code:

While Not srFile.EndOfStream
    strLine = srFile.ReadLine
    ' Split the line into parts (cell name, timestamp, color number)
    Dim parts() As String = strLine.Split({", "}, StringSplitOptions.None)
    
    If parts.Length = 3 Then
        Dim cellName As String = parts(0)
        Dim timestampStr As String = parts(1)
        Dim colorNum As String = parts(2)
        
        ' Parse the timestamp (handle invalid dates gracefully)
        Dim timestamp As DateTime
        If DateTime.TryParse(timestampStr, timestamp) Then
            ' Process Production Cell 1
            If cellName = "Production Cell 1" Then
                lstProductionCell1.Items.Add(strLine)
                
                ' Update first and last timestamps
                If firstTimeCell1 Is Nothing Then
                    firstTimeCell1 = timestamp
                End If
                lastTimeCell1 = timestamp ' Always update to the latest record
                
                ' Count colors using the parsed color number
                Select Case colorNum
                    Case "1"
                        white1 += 1
                        lblWhiteCell1.Text = white1.ToString()
                    Case "2"
                        black1 += 1
                        lblBlackCell1.Text = black1.ToString()
                    Case "3"
                        red1 += 1
                        lblRedCell1.Text = red1.ToString()
                    Case "4"
                        yellow1 += 1
                        lblYellowCell1.Text = yellow1.ToString()
                    Case "5"
                        green1 += 1
                        lblGreenCell1.Text = green1.ToString()
                    Case "6"
                        blue1 += 1
                        lblBlueCell1.Text = blue1.ToString()
                    Case "7"
                        brown1 += 1
                        lblBrownCell1.Text = brown1.ToString()
                    Case "8"
                        grey1 += 1
                        lblGreyCell1.Text = grey1.ToString()
                End Select
                
            ' Process Production Cell 2
            ElseIf cellName = "Production Cell 2" Then
                lstProductionCell2.Items.Add(strLine)
                
                ' Update first and last timestamps
                If firstTimeCell2 Is Nothing Then
                    firstTimeCell2 = timestamp
                End If
                lastTimeCell2 = timestamp ' Always update to the latest record
                
                ' Count colors using the parsed color number
                Select Case colorNum
                    Case "1"
                        white2 += 1
                        lblWhiteCell2.Text = white2.ToString()
                    Case "2"
                        black2 += 1
                        lblBlackCell2.Text = black2.ToString()
                    Case "3"
                        red2 += 1
                        lblRedCell2.Text = red2.ToString()
                    Case "4"
                        yellow2 += 1
                        lblYellowCell2.Text = yellow2.ToString()
                    Case "5"
                        green2 += 1
                        lblGreenCell2.Text = green2.ToString()
                    Case "6"
                        blue2 += 1
                        lblBlueCell2.Text = blue2.ToString()
                    Case "7"
                        brown2 += 1
                        lblBrownCell2.Text = brown2.ToString()
                    Case "8"
                        grey2 += 1
                        lblGreyCell2.Text = grey2.ToString()
                End Select
            End If
        End If
    End If
End While

Step 3: Calculate and Display Duration #

After closing the file, compute the time difference between the first and last timestamps for each cell and display it (add labels like lblDurationCell1 and lblDurationCell2 to your form first):

srFile.Close() ' Be sure to close the file

' Calculate duration for Production Cell 1
If firstTimeCell1 IsNot Nothing AndAlso lastTimeCell1 IsNot Nothing Then
    Dim duration As TimeSpan = lastTimeCell1.Value - firstTimeCell1.Value
    lblDurationCell1.Text = $"Cell 1 Total Duration: {duration.Hours}h {duration.Minutes}m {duration.Seconds}s"
Else
    lblDurationCell1.Text = "No data for Production Cell 1"
End If

' Calculate duration for Production Cell 2
If firstTimeCell2 IsNot Nothing AndAlso lastTimeCell2 IsNot Nothing Then
    Dim duration As TimeSpan = lastTimeCell2.Value - firstTimeCell2.Value
    lblDurationCell2.Text = $"Cell 2 Total Duration: {duration.Hours}h {duration.Minutes}m {duration.Seconds}s"
Else
    lblDurationCell2.Text = "No data for Production Cell 2"
End If

Key Improvements: #

• Efficient Timestamp Tracking: We capture timestamps as we read the file, avoiding re-parsing strings from ListBox items later.
• Reliable Parsing: Using Split instead of Contains makes the code less error-prone (e.g., no false matches if a timestamp accidentally contains "1").
• Error Handling: DateTime.TryParse ensures invalid timestamps don't crash your app.
• Cleaner Color Counting: The Select Case statement replaces the long chain of If/ElseIf checks for colors.

内容的提问来源于stack exchange，提问作者AaronM