c# - 为什么这段代码总是得到 SynchronizationLockException？

Question

这段代码有什么问题？

我总是得到一个

Object synchronization method was called from an unsynchronized block of code

异常(exception)情况

System.Threading.Monitor.Exit(m_sqlConnection)

但是...无论我将 Monitor 语句放在 try-catch-finally-block 的内部还是外部，以任何组合，我总是会遇到此异常。

也就是我编译代码之后。如果我在得到第一个异常后让它再次运行，它工作正常......总是在重新编译之后...

Public Shared Function GetDataTable(ByRef strSQL As String, ByRef dt As System.Data.DataTable, Optional ByRef strTableName As String = "ThisTable") As Integer
            Dim daQueryTable As System.Data.SqlClient.SqlDataAdapter = Nothing



            Try
                System.Threading.Monitor.TryEnter(m_sqlConnection, 5000)

                If isDataBaseConnectionOpen() = False Then OpenSQLConnection()


                daQueryTable = New System.Data.SqlClient.SqlDataAdapter(strSQL, m_sqlConnection)
                dt = New System.Data.DataTable(strTableName)

                daQueryTable.Fill(dt)
            Catch ex As Exception
                Log(ex)
                Return -1
            Finally
                m_sqlConnection.Close()
                System.Threading.Monitor.Exit(m_sqlConnection)
                daQueryTable.Dispose()
                daQueryTable = Nothing
            End Try

            Return dt.Rows.Count
        End Function ' GetDataTable

C#版本:

public static int GetDataTable(ref string strSQL, ref System.Data.DataTable dt, ref string strTableName = "ThisTable")
{
    System.Data.SqlClient.SqlDataAdapter daQueryTable = null;



    try {
        System.Threading.Monitor.TryEnter(m_sqlConnection, 5000);

        if (isDataBaseConnectionOpen() == false)
            OpenSQLConnection();


        daQueryTable = new System.Data.SqlClient.SqlDataAdapter(strSQL, m_sqlConnection);
        dt = new System.Data.DataTable(strTableName);

        daQueryTable.Fill(dt);
    } catch (Exception ex) {
        Log(ex);
        return -1;
    } finally {
        m_sqlConnection.Close();
        System.Threading.Monitor.Exit(m_sqlConnection);
        daQueryTable.Dispose();
        daQueryTable = null;
    }

    return dt.Rows.Count;
} // GetDataTable

Answer 1

您正在调用 TryEnter ，但忽略结果 - 所以即使您不拥有它，您也会尝试退出监视器。如果 TryEnter 返回 false，您应该采取适当的措施，例如退出该方法。