Reading From a Text File in C#

Question

I have the following program that will send (output) information to a text file, but now I want to read (input) from the text file. Any suggestions would be greatly appreciated. I have commented out a couple of things that "I think" I need to do; but I am not really certain how to proceed.

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

To read a text file one line at a time you can do like this:

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.     } } 

There are other ways as well. For example, if the file isn't too big and you just want everything read to a single string, you can use File.ReadAllText()

myTextBox.Text = File.ReadAllText(fileName);