StreamReader.Read StreamReader.Read StreamReader.Read StreamReader.Read Method

Definition

Reads the next character or next set of characters from the input stream.

Overloads

Read() Read() Read() Read()

Reads the next character from the input stream and advances the character position by one character.

Read(Span<Char>) Read(Span<Char>) Read(Span<Char>) Read(Span<Char>)
Read(Char[], Int32, Int32) Read(Char[], Int32, Int32) Read(Char[], Int32, Int32) Read(Char[], Int32, Int32)

Reads a specified maximum of characters from the current stream into a buffer, beginning at the specified index.

Read() Read() Read() Read()

Reads the next character from the input stream and advances the character position by one character.

public:
 override int Read();
public override int Read ();
override this.Read : unit -> int
Public Overrides Function Read () As Integer
Returns

The next character from the input stream represented as an Int32 object, or -1 if no more characters are available.

Exceptions

Examples

The following code example demonstrates a simple use of the Read method.

using namespace System;
using namespace System::IO;
int main()
{
   String^ path = "c:\\temp\\MyTest.txt";
   try
   {
      if ( File::Exists( path ) )
      {
         File::Delete( path );
      }
      StreamWriter^ sw = gcnew StreamWriter( path );
      try
      {
         sw->WriteLine( "This" );
         sw->WriteLine( "is some text" );
         sw->WriteLine( "to test" );
         sw->WriteLine( "Reading" );
      }
      finally
      {
         delete sw;
      }

      StreamReader^ sr = gcnew StreamReader( path );
      try
      {
         while ( sr->Peek() >= 0 )
         {
            Console::Write( (Char)sr->Read() );
         }
      }
      finally
      {
         delete sr;
      }
   }
   catch ( Exception^ e ) 
   {
      Console::WriteLine( "The process failed: {0}", e );
   }
}
using System;
using System.IO;

class Test 
{
	
    public static void Main() 
    {
        string path = @"c:\temp\MyTest.txt";

        try 
        {
            if (File.Exists(path)) 
            {
                File.Delete(path);
            }

            using (StreamWriter sw = new StreamWriter(path)) 
            {
                sw.WriteLine("This");
                sw.WriteLine("is some text");
                sw.WriteLine("to test");
                sw.WriteLine("Reading");
            }

            using (StreamReader sr = new StreamReader(path)) 
            {
                while (sr.Peek() >= 0) 
                {
                    Console.Write((char)sr.Read());
                }
            }
        } 
        catch (Exception e) 
        {
            Console.WriteLine("The process failed: {0}", e.ToString());
        }
    }
}
Imports System
Imports System.IO
Imports System.Text

Public Class Test

    Public Shared Sub Main()
        Dim path As String = "c:\temp\MyTest.txt"

        Try
            If File.Exists(path) Then
                File.Delete(path)
            End If

            Dim sw As StreamWriter = New StreamWriter(path)
            sw.WriteLine("This")
            sw.WriteLine("is some text")
            sw.WriteLine("to test")
            sw.WriteLine("Reading")
            sw.Close()

            Dim sr As StreamReader = New StreamReader(path)

            Do While sr.Peek() >= 0
                Console.Write(Convert.ToChar(sr.Read()))
            Loop
            sr.Close()
        Catch e As Exception
            Console.WriteLine("The process failed: {0}", e.ToString())
        End Try
    End Sub
End Class

The following code example demonstrates reading a single character using the Read() method overload, formatting the ASCII integer output as decimal and hexadecimal.

using namespace System;
using namespace System::IO;
int main()
{
   
   //Create a FileInfo instance representing an existing text file.
   FileInfo^ MyFile = gcnew FileInfo( "c:\\csc.txt" );
   
   //Instantiate a StreamReader to read from the text file.
   StreamReader^ sr = MyFile->OpenText();
   
   //Read a single character.
   int FirstChar = sr->Read();
   
   //Display the ASCII number of the character read in both decimal and hexadecimal format.
   Console::WriteLine( "The ASCII number of the first character read is {0:D} in decimal and {1:X} in hexadecimal.", FirstChar, FirstChar );
   
   //
   sr->Close();
}

using System;
using System.IO;

class StrmRdrRead
{
public static void Main()
    {
    //Create a FileInfo instance representing an existing text file.
    FileInfo MyFile=new FileInfo(@"c:\csc.txt");
    //Instantiate a StreamReader to read from the text file.
    StreamReader sr=MyFile.OpenText();
    //Read a single character.
    int FirstChar=sr.Read();
    //Display the ASCII number of the character read in both decimal and hexadecimal format.
    Console.WriteLine("The ASCII number of the first character read is {0:D} in decimal and {1:X} in hexadecimal.",
        FirstChar, FirstChar);
    //
    sr.Close();
    }
}
Imports System
Imports System.IO

Class StrmRdrRead
   
   Public Shared Sub Main()
      'Create a FileInfo instance representing an existing text file.
      Dim MyFile As New FileInfo("c:\csc.txt")
      'Instantiate a StreamReader to read from the text file.
      Dim sr As StreamReader = MyFile.OpenText()
      'Read a single character.
      Dim FirstChar As Integer = sr.Read()
      'Display the ASCII number of the character read in both decimal and hexadecimal format.
      Console.WriteLine("The ASCII number of the first character read is {0:D} in decimal and {1:X} in hexadecimal.", FirstChar, FirstChar)
      sr.Close()
   End Sub 'Main
End Class 'StrmRdrRead

Remarks

This method overrides TextReader.Read.

This method returns an integer so that it can return -1 if the end of the stream has been reached. If you manipulate the position of the underlying stream after reading data into the buffer, the position of the underlying stream might not match the position of the internal buffer. To reset the internal buffer, call the DiscardBufferedData method; however, this method slows performance and should be called only when absolutely necessary.

For a list of common I/O tasks, see Common I/O Tasks.

See Also

Read(Span<Char>) Read(Span<Char>) Read(Span<Char>) Read(Span<Char>)

public:
 override int Read(Span<char> buffer);
public override int Read (Span<char> buffer);
override this.Read : Span<char> -> int
Public Overrides Function Read (buffer As Span(Of Char)) As Integer
Parameters
buffer
Span<Char>
Returns

Read(Char[], Int32, Int32) Read(Char[], Int32, Int32) Read(Char[], Int32, Int32) Read(Char[], Int32, Int32)

Reads a specified maximum of characters from the current stream into a buffer, beginning at the specified index.

public:
 override int Read(cli::array <char> ^ buffer, int index, int count);
public override int Read (char[] buffer, int index, int count);
override this.Read : char[] * int * int -> int
Public Overrides Function Read (buffer As Char(), index As Integer, count As Integer) As Integer
Parameters
buffer
Char[]

When this method returns, contains the specified character array with the values between index and (index + count - 1) replaced by the characters read from the current source.

index
Int32 Int32 Int32 Int32

The index of buffer at which to begin writing.

count
Int32 Int32 Int32 Int32

The maximum number of characters to read.

Returns

The number of characters that have been read, or 0 if at the end of the stream and no data was read. The number will be less than or equal to the count parameter, depending on whether the data is available within the stream.

Exceptions

The buffer length minus index is less than count.

An I/O error occurs, such as the stream is closed.

Examples

The following code example reads five characters at a time until the end of the file is reached.

using namespace System;
using namespace System::IO;

int main()
{
   String^ path = "c:\\temp\\MyTest.txt";
   try
   {
      if ( File::Exists( path ) )
      {
         File::Delete( path );
      }
      StreamWriter^ sw = gcnew StreamWriter( path );
      try
      {
         sw->WriteLine( "This" );
         sw->WriteLine( "is some text" );
         sw->WriteLine( "to test" );
         sw->WriteLine( "Reading" );
      }
      finally
      {
         delete sw;
      }

      StreamReader^ sr = gcnew StreamReader( path );
      try
      {
         //This is an arbitrary size for this example.
         array<Char>^c = nullptr;
         while ( sr->Peek() >= 0 )
         {
            c = gcnew array<Char>(5);
            sr->Read( c, 0, c->Length );
            
            //The output will look odd, because
            //only five characters are read at a time.
            Console::WriteLine( c );
         }
      }
      finally
      {
         delete sr;
      }
   }
   catch ( Exception^ e ) 
   {
      Console::WriteLine( "The process failed: {0}", e );
   }
}
using System;
using System.IO;

class Test 
{
	
    public static void Main() 
    {
        string path = @"c:\temp\MyTest.txt";

        try 
        {
            if (File.Exists(path)) 
            {
                File.Delete(path);
            }

            using (StreamWriter sw = new StreamWriter(path)) 
            {
                sw.WriteLine("This");
                sw.WriteLine("is some text");
                sw.WriteLine("to test");
                sw.WriteLine("Reading");
            }

            using (StreamReader sr = new StreamReader(path)) 
            {
                //This is an arbitrary size for this example.
                char[] c = null;

                while (sr.Peek() >= 0) 
                {
                    c = new char[5];
                    sr.Read(c, 0, c.Length);
                    //The output will look odd, because
                    //only five characters are read at a time.
                    Console.WriteLine(c);
                }
            }
        } 
        catch (Exception e) 
        {
            Console.WriteLine("The process failed: {0}", e.ToString());
        }
    }
}
Imports System
Imports System.IO
Imports System.Text

Public Class Test

    Public Shared Sub Main()
        Dim path As String = "c:\temp\MyTest.txt"

        Try
            If File.Exists(path) Then
                File.Delete(path)
            End If

            Dim sw As StreamWriter = New StreamWriter(path)
            sw.WriteLine("This")
            sw.WriteLine("is some text")
            sw.WriteLine("to test")
            sw.WriteLine("Reading")
            sw.Close()

            Dim sr As StreamReader = New StreamReader(path)

            Do While sr.Peek() >= 0
                'This is an arbitrary size for this example.
                Dim c(5) As Char
                sr.Read(c, 0, c.Length)
                'The output will look odd, because
                'only five characters are read at a time.
                Console.WriteLine(c)
            Loop
            sr.Close()
        Catch e As Exception
            Console.WriteLine("The process failed: {0}", e.ToString())
        End Try
    End Sub
End Class

Remarks

This method overrides TextReader.Read.

This method returns an integer so that it can return 0 if the end of the stream has been reached.

When using the Read method, it is more efficient to use a buffer that is the same size as the internal buffer of the stream, where the internal buffer is set to your desired block size, and to always read less than the block size. If the size of the internal buffer was unspecified when the stream was constructed, its default size is 4 kilobytes (4096 bytes). If you manipulate the position of the underlying stream after reading data into the buffer, the position of the underlying stream might not match the position of the internal buffer. To reset the internal buffer, call the DiscardBufferedData method; however, this method slows performance and should be called only when absolutely necessary.

This method returns after either the number of characters specified by the count parameter are read, or the end of the file is reached. ReadBlock is a blocking version of Read.

For a list of common I/O tasks, see Common I/O Tasks.

See Also

Applies to