StreamReader.Read Method (System.IO) (2023)

public: override int Read();

public override int Read ();

override this.Read : unit -> int

Public Overrides Function Read () As Integer

Returns

Int32

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.IOImports System.TextPublic 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 SubEnd 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.IOClass 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 SubEnd Class

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

• File and Stream I/O
• How to: Read Text from a File
• How to: Write Text to a File

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

Returns

Int32

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 buffer length, depending on whether the data is available within the stream.

Exceptions

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

Returns

Int32

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

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.IOImports System.TextPublic 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 SubEnd 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

• File and Stream I/O
• How to: Read Text from a File
• How to: Write Text to a File