c# 使用FileStream打開並清空文件、將一文件內容另存爲到新文件

*以下爲使用FileStream方式打開並清空文件： 

FileStream fs = null;
            try
            {
                fs = new FileStream(m_LogFilePath, FileMode.Truncate, FileAccess.ReadWrite);

            }
            catch (Exception ex)
            {
                Trace.Write("清空日誌文件失敗：" + ex.Message);
            }
            finally
            {
                fs.Close();
            }

注意：對文件進行讀寫操作，最好都用try-catch。

          在使用FileMode.Truncate時，FileAccess不能使用FileAccess.Read;仔細想想也知道，此種模式其實，是需要先將文件中的內容清空。

 

*以下爲將一文件內容另存爲到新文件：

 SaveFileDialog saveFileDialog = new SaveFileDialog();
            saveFileDialog.Filter = "文本文件(*.txt)|*.txt";
            saveFileDialog.Title = "另存爲";
            if (saveFileDialog.ShowDialog() == DialogResult.OK)
            {
                FileStream fs = null;
                StreamWriter sw = null;
                StreamReader sr = null;
                try
                {
                    fs = new FileStream(saveFileDialog.FileName, FileMode.Create, FileAccess.ReadWrite);
                    fs.Close();

                    sr = new StreamReader(m_LogFilePath);//m_LogFilePath爲需要另存爲的文件的路徑
                    sw = new StreamWriter(saveFileDialog.FileName);
                    sw.Write(sr.ReadToEnd());
                    sw.Flush();
                }
                catch (Exception ex)
                {
                    Trace.Write("清空日誌文件失敗：" + ex.Message);
                }
                finally
                {
                    if(fs!=null)
                        fs.Close();
                    sw.Close();
                    sr.Close();
                }
            }