Lettura da un file di testo in C#

Question

Ho il seguente programma che invierà (output) informazioni a un file di testo, ma ora voglio leggere (input) dal file di testo. Ogni suggerimento sarà molto apprezzato. Ho commentato un paio di cose che "penso" ho bisogno di fare; ma non sono veramente sicuro di come procedere.

using System.Windows.Forms; 
using System.IO; 

namespace Input_Output 
{ 
    public partial class Grades : Form 
    { 
     private StreamWriter output; 

     private StreamReader input; 


     public Grades() 
     { 
      InitializeComponent(); 
     } 

     private void label4_Click(object sender, EventArgs e) 
     { 

     } 

     private void btnCreate_Click(object sender, EventArgs e) 
     { 
      btnEnter.Visible = true; 
      btnClose.Visible = true; 
      txtFirst.Visible = true; 
      txtLast.Visible = true; 
      lblFirst.Visible = true; 
      lblLast.Visible = true; 
      listBox1.Visible = true; 
      lblStatus.Visible = true; 
      lblGrade.Visible = true; 
      lblCourse.Visible = true; 
      cmbID.Visible = true; 
      lblID.Visible = true; 
      txtCourse.Visible = true; 
      txtGrade.Visible = true; 
      lblStatus.Visible = true; 

      DialogResult result; 
      string fileName; 
      using (SaveFileDialog chooser = new SaveFileDialog()) 
      { 
       result = chooser.ShowDialog(); 
       fileName = chooser.FileName; 
      } 
      output = new StreamWriter(fileName); 
      btnCreate.Enabled = false; 
      txtFirst.Visible = true; 
      txtLast.Visible = true; 
      lblFirst.Visible = true; 
      lblLast.Visible = true; 
      btnEnter.Visible = true; 
      btnClose.Visible = true; 
     } 


     private void btnClose_Click(object sender, EventArgs e) 
     { 
      //Close button pushes information from the listbox in to the text file 

      output.Close(); 
      lblStatus.ForeColor = Color.Red; 
      lblStatus.Text = "Output File"; 
      btnCreate.Enabled = true; 
      listBox1.Items.Clear(); 
      cmbID.Text = ""; 
     } 

     private void btnEnter_Click(object sender, EventArgs e) 
     { 
      // Enter button sends information to the list box, a Message Box prompts user to check for accuracy. 
      //Close button pushes information to the Text file. 
      string last = ""; 
      string first = ""; 
      string course = ""; 
      string grade = ""; 

      if (txtFirst.Text != "" && txtLast.Text != "" && txtCourse.Text != "") 
      { 
       last = txtFirst.Text; 
       first = txtLast.Text; 
       course = txtCourse.Text; 
       grade = txtGrade.Text; 
       output.WriteLine (last + "\t"+ "\t" + first + ":"+ "\t" + cmbID.SelectedItem + "_" + course + "_" + grade); 

       listBox1.Items.Add(txtLast.Text + "," + txtFirst.Text + ":" + cmbID.SelectedItem + "-" + txtCourse.Text + "-" + txtGrade.Text); 
       lblStatus.ForeColor = Color.Navy; 
       lblStatus.Text = "Entry Saved"; 
       txtFirst.Text = ""; 
       txtLast.Text = ""; 
       txtCourse.Text = ""; 
       txtGrade.Text = ""; 
       txtFirst.Focus(); 
      } 
      else 
      {  
       lblStatus.ForeColor = Color.Red; 
       lblStatus.Text = "Empty text box or boxes"; 
      } 
      MessageBox.Show("Please verify that the information is correct before proceeding"); 
     } 

     private void btnExit_Click(object sender, EventArgs e) 
     { 
      Application.Exit(); 
     } 

     private void Grades_Load(object sender, EventArgs e) 
     { 

     } 

     private void button1_Click(object sender, EventArgs e) 
     { 
      DialogResult result; 
      string fileName; 
      using (OpenFileDialog chooser = new OpenFileDialog()) 
      { 
       result = chooser.ShowDialog(); 
       fileName = chooser.FileName; 
      } 
      //while loop? 
      //if variable is null, it's the end of the record 
      //variable= !null 
      //txt read int variable TxtFile.Text += Rec + "\r\n"; while rec !=null; 
     } 
    } 
} 

Answer 1

Prova questo:

if(result == DialogResult.OK && fileName != null) 
{ 
    try 
    { 
     var fileText=File.ReadAllText(fileName); 
    } 
    catch(Exception ex) 
    { 
     //Handle exception here 
    } 
} 

Sarà leggere tutti i dati dal file selezionato nella variabile fileText.

Answer 2

Per leggere un file di testo una riga alla volta si può fare in questo modo:

using System.IO; 

using (var reader = new StreamReader(fileName)) 
{ 
    string line; 
    while ((line = reader.ReadLine()) != null) 
    { 
     // Do stuff with your line here, it will be called for each 
     // line of text in your file. 
    } 
} 

Non ci sono altri modi. Ad esempio, se il file non è troppo grande e si vuole proprio tutto di leggere ad una singola stringa, è possibile utilizzare File.ReadAllText()

myTextBox.Text = File.ReadAllText(fileName); 

Answer 3

Controllare questo codice:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click 
    Dim myStream As Stream = Nothing 
    Dim openFileDialog1 As New OpenFileDialog() 

    'openFileDialog1.InitialDirectory = "c:\" 
    openFileDialog1.Filter = "txt files (*.txt)|*.txt|All files (*.*)|*.*" 
    openFileDialog1.FilterIndex = 1 
    openFileDialog1.RestoreDirectory = True 

    If openFileDialog1.ShowDialog() = System.Windows.Forms.DialogResult.OK Then 
     Try 
      myStream = openFileDialog1.OpenFile() 
      If (myStream IsNot Nothing) Then 
       dataFile = openFileDialog1.FileName 
       Label1.Text = openFileDialog1.SafeFileName 

       Dim myReader As New StreamReader(dataFile) 
       Dim line As String 
       line = myReader.ReadLine() 
       While Not (line Is Nothing) 
        Dim str() As String = Split(line, ControlChars.Tab) 
        ListView1.Items.Add(New ListViewItem(str)) 
        line = myReader.ReadLine() 
       End While 

       myReader.Close() 
      End If 
     Catch Ex As Exception 
      MessageBox.Show("Cannot read file from disk. Original error: " & Ex.Message) 
     Finally 
      ' Check this again, since we need to make sure we didn't throw an exception on open. 
      If (myStream IsNot Nothing) Then 
       myStream.Close() 
      End If 
     End Try 
    End If 
End Sub 

Answer 4

E 'solo una riga di codice :

string content = System.IO.File.ReadAllText(@"C:\textfile.txt"); 

Answer 5

Usa Split(), come nel seguente codice

using System; 
 
using System.Collections.Generic; 
 
using System.Linq; 
 
using System.Text; 
 
using System.IO; 
 

 
namespace ConsoleApplication1 
 
{ 
 
    class Program 
 
    { 
 
     const string FILENAME = @"C:\temp\test.txt"; 
 
     static void Main(string[] args) 
 
     { 
 
      StreamReader reader = new StreamReader(FILENAME); 
 
      string inputLine = ""; 
 
      List<List<int>> data = new List<List<int>>(); 
 
      while ((inputLine = reader.ReadLine()) != null) 
 
      { 
 
       string[] inputArray = inputLine.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries); 
 
       if (inputArray.Count() > 0) 
 
       { 
 
        List<int> numbers = inputArray.Select(x => int.Parse(x)).ToList(); 
 
        data.Add(numbers); 
 
       } 
 
      } 
 
      
 
     } 
 
     
 
    } 
 
} 
 
​

Answer 6

using System; 
using System.Collections.Generic; 
using System.ComponentModel; 
using System.Data; 
using System.Drawing; 
using System.Linq; 
using System.Text; 
using System.Threading.Tasks; 
using System.Windows.Forms; 
using System.IO; 

namespace part_B_19 
{ 
    public partial class Form1 : Form 
    { 
     public Form1() 
     { 
      InitializeComponent(); 
     } 

     private void button1_Click(object sender, EventArgs e) 
     { 
      try 
      { 
       StreamReader sr = new StreamReader(@"C:\Users\Acer\Documents\Visual Studio 2012\Projects\combobox.txt"); 
       string line = sr.ReadLine(); 

       while (line != null) 
       { 
        comboBox1.Items.Add(line); 
        line = sr.ReadLine(); 
       } 
      } 
      catch(Exception ex) 
      { 
       MessageBox.Show(ex.Message); 
      } 


     } 
    } 
} 

Answer 7

Programma di esempio dimostrando I/O file in C#

class Items 
{ 
    public int itemID { get; set; } 
    public string itemName { get; set; } 
    public int itemNo { get; set; } 
    public string pkgdate { get; set; } 
} 

class Program 
{ 
    private static string connectionString = "..."; 

    static void Main(string[] args) 
    { 
    string streadpath = @"I:\itemdata.txt"; 
    string stwritepath = @"I:\itemdata1.txt"; 
    string stcopypath = @"I:\itemdata2.txt"; 

    List<Items> li_all = new List<Items>(); 
    List<Items> li_db = new List<Items>(); 
    List<Items> li_valid = new List<Items>(); 
    List<Items> li_invalid = new List<Items>(); 

    li_all = stread_file(streadpath); 
    li_invalid = validate(li_all); 
    li_db = retrievefromDB(); 
    bool x = stwrite_invalid(li_db, stwritepath); 
    bool y = stcopy_file(streadpath, stcopypath); 
    } 

    static List<Items> stread_file(string stpath) 
    { 
    List<Items> stli = new List<Items>(); 
    using (StreamReader SR = new StreamReader(stpath)) 
    { 
     string line = ""; 
     while ((line = SR.ReadLine()) != null) 
     { 
     string[] linevalues = line.Split(','); 
     Items obj = new Items(); 
     obj.itemID = int.Parse(linevalues[0]); 
     obj.itemName = linevalues[1]; 
     obj.itemNo = int.Parse(linevalues[2]); 
     obj.pkgdate = linevalues[3]; 
     stli.Add(obj); 
     } 
    } 
    return stli; 
    } 

    static List<Items> validate(List<Items> stli) 
    { 
    List<Items> li_valid = new List<Items>(); 
    List<Items> li_invalid = new List<Items>(); 
    DateTime parsed; 
    foreach (Items stit in stli) 
    { 
     if(DateTime.TryParseExact(stit.pkgdate, "MM/dd/yyyy", 
     CultureInfo.InvariantCulture, 
     DateTimeStyles.None, out parsed)) 
     { 
     li_valid.Add(stit); 
     } 
     else 
     { 
     li_invalid.Add(stit); 
     } 
    } 
    InsertDataToDb(li_valid); 
    return li_invalid; 
    } 

    static bool stwrite_invalid(List<Items> stli,string stpath) 
    { 
    using (StreamWriter SW = new StreamWriter(stpath)) 
    { 
     foreach(Items stit in stli) 
     { 
     SW.WriteLine(stit.itemID + "," + stit.itemName + "," + stit.itemNo + "," + stit.pkgdate); 
     } 
    } 
    return true; 
    } 

    static bool stcopy_file(string stsourcepath, string stdestinationpath) 
    { 
    File.Copy(stsourcepath, stdestinationpath); 
    return true; 
    } 

    static void InsertDataToDb(List<Items> stli) 
    { 
    var records = stli; 
    using (SqlConnection con = new SqlConnection(connectionString)) 
    { 
     StringBuilder nonQuery = new StringBuilder(); 
     foreach (var item in records) 
     { 
     nonQuery.AppendFormat("INSERT INTO dbo.Smartphone VALUES ({0}, '{1}', {2}, '{3}');", 
     item.itemID, 
     item.itemName, 
     item.itemNo, 
     item.pkgdate); 
     } 
     SqlCommand cmd = new SqlCommand(nonQuery.ToString(),con); 
     con.Open(); 
     cmd.ExecuteNonQuery(); 
     con.Close(); 
    } 
    } 

    static List<Items> retrievefromDB() 
    { 
    List<Items> stli = new List<Items>(); 
    DataTable dt = new DataTable(); 
    SqlConnection con = new SqlConnection(connectionString); 
    con.Open(); 
    SqlCommand cmd = new SqlCommand("select * from dbo.Smartphone", con); 
    SqlDataAdapter da = new SqlDataAdapter(cmd); 
    da.Fill(dt); 
    con.Close(); 
    if (dt.Rows.Count > 0) 
    { 
     for (int i = 0; i < dt.Rows.Count; i++) 
     { 
     Items obj = new Items(); 
     obj.itemID = (int)dt.Rows[i]["ID"]; 
     obj.itemName = dt.Rows[i]["Name"].ToString(); 
     obj.itemNo = (int)dt.Rows[i]["Num"]; 
     obj.pkgdate = dt.Rows[i]["RDate"].ToString(); 
     stli.Add(obj); 
     } 
    } 
    return stli; 
    } 
}