无法从字符串转换为system.io.stream [英] Cannot convert from string to system.io.stream
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问题描述
在第366行，我收到错误无法从字符串转换为System.IO.Stream。
和第383行，我正在获取streamwriter不包含关闭的定义。
On line 366 , i am getting error cannot convert from string to System.IO.Stream.
and on line 383, i am getting streamwriter does not contain a definition for close.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using MySql.Data.MySqlClient;
using System.Diagnostics;
using System.IO;
namespace connect
{
class DBConnect
{
private MySqlConnection connection;
private string server;
private string database;
private string uid;
private string password;
//Constructor
public DBConnect()
{
Initialize();
}
//Initialize values
private void Initialize()
{
server = "localhost";
database = "first_db";
uid = "root";
password = "";
string connectionString;
connectionString = "SERVER=" + server + ";" + "DATABASE=" +
database + ";" + "UID=" + uid + ";" + "PASSWORD=" + password + ";";
connection = new MySqlConnection(connectionString);
this.display();
}
// displays the database
public void display()
{
// a is the number of rows
int a = -1;
a = this.Countrows();
//Console.WriteLine(a);
// b is the number of columns
int b = this.Countcolumns();
//Console.WriteLine(b);
//create a new list with 3 columns , b = 3; b is the number of columns
List<string>[] newlist = new List<string>[b];
// this.Select() fetches the dataset, set it to equal to newlist
newlist = this.Select();
Console.WriteLine("Id" + " " + "username" + " " + "password");
for (int j = 0; j < a; j++) // iterate through each row; a is total number of rows
{
for (int i = 0; i < b; i++) // ITERATE THROUGH EACH COLUMN ; b is total number of columns
{
Console.Write(newlist[i][j] + " ");
}
// for each row of obsv..write a new line
Console.WriteLine();
}
}
//open connection to database
public bool OpenConnection()
{
try
{
connection.Open();
Console.WriteLine("connection opened");
return true;
}
catch (MySqlException ex)
{
//When handling errors, you can your application's response based
//on the error number.
//The two most common error numbers when connecting are as follows:
//0: Cannot connect to server.
//1045: Invalid user name and/or password.
switch (ex.Number)
{
case 0:
Console.WriteLine("Cannot connect to server. Contact administrator");
break;
case 1045:
Console.WriteLine("Invalid username/password, please try again");
break;
}
return false;
}
}
//Close connection
public bool CloseConnection()
{
try
{
connection.Close();
Console.WriteLine("connection closed");
return true;
}
catch (MySqlException ex)
{
Console.WriteLine(ex.Message);
return false;
}
}
//Insert statement
public void Insert()
{
string query = "INSERT INTO users (id, username, password) VALUES('23' ,'Jojo', '33') , ('99', 'jen', '66')";
//open connection
if (this.OpenConnection() == true)
{
//create command and assign the query and connection from the constructor
MySqlCommand cmd = new MySqlCommand(query, connection);
Console.WriteLine("values inserted");
//Execute command
cmd.ExecuteNonQuery();
//close connection
this.CloseConnection();
}
}
//Update statement
public void Update()
{
string query = "UPDATE users SET username='Joe', password='22', id='33' WHERE username='Joe'";
//Open connection
if (OpenConnection() == true)
{
//create mysql command
MySqlCommand cmd = new MySqlCommand();
//Assign the query using CommandText
cmd.CommandText = query;
//Assign the connection using Connection
cmd.Connection = connection;
//Execute query
cmd.ExecuteNonQuery();
//close connection
this.CloseConnection();
}
}
//Delete statement
public void Delete()
{
string query = "DELETE FROM users WHERE username='Joe'";
if (this.OpenConnection() == true)
{
MySqlCommand cmd = new MySqlCommand(query, connection);
cmd.ExecuteNonQuery();
this.CloseConnection();
}
}
//Select statement
public List<string>[] Select()
{
string query = "SELECT * FROM users";
//Create a list of 3 elements to store the result
List<string>[] list = new List<string>[3];
// each element of list is a new list of strings
list[0] = new List<string>();
list[1] = new List<string>();
list[2] = new List<string>();
//Open connection, running OpenConnection() will open the connection
if (this.OpenConnection() == true)
{
//Create Command
MySqlCommand cmd = new MySqlCommand(query, connection);
//Create a data reader and Execute the command
MySqlDataReader dataReader = cmd.ExecuteReader();
//Read the data and store them in the list
// iterate through each row... dataReader.Read will get the data for each row...
while (dataReader.Read())
{
// iterate through each column, add the id , username, password list[0] is column1 which is id, list[1] IS COLUMN2 WHICH IS USERNAME... list[0][0] element column 1 , row 1
list[0].Add(dataReader["id"] + "");
list[1].Add(dataReader["username"] + "");
list[2].Add(dataReader["password"] + "");
}
//close Data Reader
dataReader.Close();
//close Connection
this.CloseConnection();
//return list to be displayed
return list;
}
else
{
return list;
}
}
//Count statement
public int Countrows()
{
string query = "SELECT Count(*) FROM users";
int Count = -1;
//Open Connection
if (this.OpenConnection() == true)
{
//Create Mysql Command
MySqlCommand cmd = new MySqlCommand(query, connection);
//ExecuteScalar will return one value
Count = int.Parse(cmd.ExecuteScalar() + "");
//close Connection
this.CloseConnection();
return Count;
}
else
{
return Count;
}
}
public int Countcolumns()
{
string query = "SELECT Count(*) FROM INFORMATION_SCHEMA.COLUMNS WHERE table_schema = 'first_db' AND table_name = 'users'";
int Count = -1;
//Open Connection
if (this.OpenConnection() == true)
{
//Create Mysql Command
MySqlCommand cmd = new MySqlCommand(query, connection);
//ExecuteScalar will return one value
Count = int.Parse(cmd.ExecuteScalar() + "");
//close Connection
this.CloseConnection();
return Count;
}
else
{
return Count;
}
}
//Backup
public void Backup()
{
try
{
DateTime Time = DateTime.Now;
int year = Time.Year;
int month = Time.Month;
int day = Time.Day;
int hour = Time.Hour;
int minute = Time.Minute;
int second = Time.Second;
int millisecond = Time.Millisecond;
//Save file to C:\ with the current date as a filename
string path;
path = "C:\\MySqlBackup" + year + "-" + month + "-" + day +
"-" + hour + "-" + minute + "-" + second + "-" + millisecond + ".sql";
StreamWriter file = new StreamWriter(path);
ProcessStartInfo psi = new ProcessStartInfo();
psi.FileName = "mysqldump";
psi.RedirectStandardInput = false;
psi.RedirectStandardOutput = true;
psi.Arguments = string.Format(@"-u{0} -p{1} -h{2} {3}",
uid, password, server, database);
psi.UseShellExecute = false;
Process process = Process.Start(psi);
string output;
output = process.StandardOutput.ReadToEnd();
file.WriteLine(output);
process.WaitForExit();
file.Close();
process.Close();
}
catch (IOException ex)
{
Console.WriteLine("Error , unable to backup!");
Console.WriteLine("ex.message");
}
}
/*
//Restore
public void Restore()
{
}
*
*/
}
}
我尝试过：
我不知道该放什么。这只是一个我没有概念的错误。因为我对C＃完全不熟悉，所以我在这里谅解。
What I have tried:
I am not sure what to put here. this is just an error which i have no concept of. as i am completely new to C# , i beg your understanding here.
推荐答案
哦，你的对象错了，你写的是
Oh you got the objects wrong, what you wrote was
string path = "C:\\MySqlBackup" + year + "-" + month + "-" + day +
"-" + hour + "-" + minute + "-" + second + "-" + millisecond + ".sql";
StreamWriter file = new StreamWriter(path);
但你想做的是在制作作家之前创建流，并记住要么逃避转义字符（反斜杠）或使用编译时常量指示符（@）
But what you want to do is to create the stream before making the writer, and remember to either escape your escape characters (backslash) or use compiletime constant indicator (@)
string path = @"C:\\MySqlBackup" + year + "-" + month + "-" + day +
"-" + hour + "-" + minute + "-" + second + "-" + millisecond + ".sql";
using (var stream = new FileStream(path, FileMode.OpenOrCreate, FileAccess.Write))
{
var writer = new StreamWriter(stream, Encoding.UTF8);
writer.Write("Hello world");
writer.Flush();
writer.Close();
}
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