从字节流写入和读取

Question

我有一个页面，用户可以在其中上传自己的 csv 或将值输入到列表框中，然后创建一个 csv（在后台）。无论以哪种方式创建 csv，我都需要通过字节流将该 csv 上传到我们的服务器。

我的问题是，当我创建 csv 时，我不应该创建临时文件，我应该能够写入流然后将其读回以进行上传。如何消除对临时文件的需求？

当前有效的代码（但使用临时文件）：

try {
                string filename = DateTime.Now.ToString("MMddyyHmssf");
                filename = filename + ".csv";
                string directory = ConfigurationManager.AppSettings["TempDirectory"].ToString();
                path = Path.Combine(directory, filename);
                using (StreamWriter sw = File.CreateText(path)) {

                    foreach (ListItem item in this.lstAddEmailAddress.Items) {
                        sw.WriteLine(" , ," + item.ToString());
                    }
                }
            } catch (Exception ex) {
                string error = "Cannot create temp csv file used for importing users by email address.  Filepath: " + path + ".  FileException: " + ex.ToString();
                this.writeToLogs(error, 1338);
            }
        }
        // put here for testing the byte array being sent vs ready byte[] byteArray = System.IO.File.ReadAllBytes(path);
        myCsvFileStream = File.OpenRead(path);
        nFileLen = (int)myCsvFileStream.Length;

我试过了

Stream myCsvFileStream;
using (StreamWriter sw = new StreamWriter(myCsvFileStream)) {

                    foreach (ListItem item in this.lstAddEmailAddress.Items) {
                        sw.WriteLine(" , ," + item.ToString());

                    }
                }

但是由于 myCsvFileStream 没有被初始化（因为 stream 是一个静态类）它总是为 null。

这是我在创建 csv 后对数据（字节流）所做的操作。

byte[] file = new byte[nFileLen];
            myCsvFileStream.Read(file, 0, nFileLen);
            bool response = this.repositoryService.SaveUsers(this.SelectedAccount.Id, file, this.authenticatedUser.SessionToken.SessionId);
            myCsvFileStream.Close();

最后我使用StringBuilder 来创建我的csv 文件内容。然后得到其内容的字节数组并用它来填充我的共享流（我说共享是因为当用户输入他们自己的 CSV 文件时，它是一个HttpPostedFile，但是当通过 rest 调用将它发送到我们的服务器时（respositoryservices.saveusers ) 它使用与通过此方法相同的字节流)

StringBuilder csvFileString = new StringBuilder();

            sharedStreamForBatchImport = new MemoryStream();
            foreach (ListItem item in this.lstAddEmailAddress.Items) {
                csvFileString.Append(",," + item.ToString() + "\\r\\n");
            }

            //get byte array of the string
            byteArrayToBeSent = Encoding.ASCII.GetBytes(csvFileString.ToString());
            //set length for read
            byteArraySize = (int)csvFileString.Length;
            //read bytes into the sharedStreamForBatchImport (byte array)
            sharedStreamForBatchImport.Read(byteArrayToBeSent, 0, byteArraySize);

Answer 1

你想创建一个new MemoryStream()

Answer 2

这是我用来编写 CSV 文件的函数

    public static bool WriteCsvFile(string path, StringBuilder stringToWrite)
    {
        try
        {
            using (StreamWriter sw = new StreamWriter(path, false))         //false in ordre to overwrite the file if it already exists
            {
                sw.Write(stringToWrite);
                return true;
            }
        }
        catch (Exception)
        {
            return false;
        }
    }

stringToWrite 只是一个以这种方式创建的字符串：

    public static bool WriteCsvFile(string path, DataTable myData)
    {
        if (myData == null)
            return false;
        //Information about the table we read
        int nbRows = myData.Rows.Count;
        int nbCol = myData.Columns.Count;
        StringBuilder stringToWrite = new StringBuilder();

        //We get the headers of the table
        stringToWrite.Append(myData.Columns[0].ToString());
        for (int i = 1; i < nbCol; ++i)
        {
            stringToWrite.Append(",");
            stringToWrite.Append(myData.Columns[i].ToString());
        }
        stringToWrite.AppendLine();

        //We read the rest of the table
        for (int i = 0; i < nbRows; ++i)
        {
            stringToWrite.Append(myData.Rows[i][0].ToString());
            for (int j = 1; j < nbCol; ++j)
            {
                stringToWrite.Append(",");
                stringToWrite.Append(myData.Rows[i][j].ToString());
            }
            stringToWrite.AppendLine();
        }

        return WriteCsvFile(path, stringToWrite);
    }