在formshow中使用Streamreader跨表单使用streamreader

Question

在VS2008中使用VB.Net。我的主表单(frmMain)使用streamwriter创建日志，我将各种事件写入日志。日志变量名是" log“，所以我做了一个Log.Writeline()来post到日志中，这在主表单中工作得很好，但是如果我为选项或维护功能加载另一个表单，我不能写入日志，如果我使用一个新的streamwriter，它会给出错误。

关于如何跨表单使用流编写器有什么想法吗？我可以使用轻松访问控件。但它不能与streamwriter一起工作。

有什么想法？

Answer 1

处理这个问题的最简单方法是创建一个静态类，该类包含一个打开的StreamWriter，并使用SyncLocks来确保一次只有一个线程可以使用打开的编写器。

下面是一个简单的示例：

Imports System.IO
Imports System.Threading

Public Class ApplicationLog

    Private Shared m_LogWriter As StreamWriter

    Shared Sub New()
        Dim theType As Type
        Dim fClearSettings As Boolean = True

        ' Get the class object in order to take the initialization lock
        theType = GetType(ApplicationLog)

        ' Protect thread locks with Try/Catch to guarantee that we let go of the lock.
        Try
            ' See if anyone else is using the lock, grab it if they're not
            If Not Monitor.TryEnter(theType) Then

                ' Just wait until the other thread finishes processing, then leave if the lock was already in use.
                Monitor.Enter(theType)
                Exit Sub
            End If

            Try
                ' Create a debug listener and add it as a debug listener
                m_LogWriter = New StreamWriter(New FileInfo("C:\mylog.txt").Open(FileMode.Append, IO.FileAccess.Write, FileShare.ReadWrite))

                fClearSettings = False
            Catch
                ' Ignore the error
            End Try

            ' Rest the var if something went wrong
            If fClearSettings Then
                m_LogWriter = Nothing
            End If
        Finally
            ' Remove the lock from the class object
            Monitor.Exit(theType)
        End Try
    End Sub

    Public Shared Sub WriteToLog(ByVal sMessageText As String)
        Try
            ' Make sure a tracing file is specified.
            If m_LogWriter IsNot Nothing Then
                SyncLock m_LogWriter
                    m_LogWriter.WriteLine(sMessageText)
                    m_LogWriter.Flush()
                End SyncLock
            End If
        Catch
            ' Ignore any exceptions.
        End Try
    End Sub

End Class