File.OpenRead() Method in C# with Examples

25 Feb, 2021
File.OpenRead(String) is an inbuilt File class method which is used to open an existing file for reading.Syntax:  
public static System.IO.FileStream OpenRead (string path);
Parameter: This function accepts a parameter which is illustrated below:  
path: This is the specified file which is going to be opened for reading.
Exceptions: 
ArgumentException: The path is a zero-length string, contains only white space, or one or more invalid characters as defined by InvalidPathChars.
ArgumentNullException: The path is null.
PathTooLongException: The specified path, file name, or both exceed the system-defined maximum length.
DirectoryNotFoundException: The specified path is invalid.
UnauthorizedAccessException: The path specified a directory. OR the caller does not have the required permission.
FileNotFoundException: The file specified in the path was not found.
NotSupportedException: The path is in an invalid format.
IOException: An I/O error occurred while opening the file.
Return Value: Returns a read-only FileStream on the specified path.Below are the programs to illustrate the File.OpenRead(String) method.Program 1: Before running the below code, a file file.txt is created with some contents shown below 
Below code open the file file.txt for reading. 
C#
// C# program to illustrate the usage// of File.OpenRead(String) method  // Using System, System.IO and// System.Text namespacesusing System;using System.IO;using System.Text;  class Test {    public static void Main()    {        // Specifying a file        string path = @"file.txt";          // Opening the existing file for reading        using(FileStream fs = File.OpenRead(path))        {            byte[] b = new byte[1024];            UTF8Encoding temp = new UTF8Encoding(true);              while (fs.Read(b, 0, b.Length) > 0) {                // Printing the file contents                Console.WriteLine(temp.GetString(b));            }        }    }}
Executing:  
GeeksforGeeks
Program 2: Initially, a file file.txt is created with some contents shown below- 
This below code will overwrite the file contents with other specified contents then final contents will be printed. 
C#
// C# program to illustrate the usage// of File.OpenRead(String) method  // Using System, System.IO and// System.Text namespacesusing System;using System.IO;using System.Text;  class GFG {    public static void Main()    {        // Specifying a file        string path = @"file.txt";          // Opening the file for overwriting with        // another contents        using(FileStream fs = File.OpenWrite(path))        {            Byte[] info = new UTF8Encoding(true).GetBytes("GFG is a CS portal.");            fs.Write(info, 0, info.Length);        }          // Opening the existing file for reading        using(FileStream fs = File.OpenRead(path))        {            byte[] b = new byte[1024];            UTF8Encoding temp = new UTF8Encoding(true);              while (fs.Read(b, 0, b.Length) > 0) {                // Printing the file contents                Console.WriteLine(temp.GetString(b));            }        }    }}
Executing:
GFG is a CS portal.
arorakashish0911
CSharp-File-Handling
C#
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