File.OpenRead() Method in C# with Examples
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#
using System;
using System.IO;
using System.Text;
class Test {
public static void Main()
{
string path = @"file.txt" ;
using (FileStream fs = File.OpenRead(path))
{
byte [] b = new byte [1024];
UTF8Encoding temp = new UTF8Encoding( true );
while (fs.Read(b, 0, b.Length) > 0) {
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#
using System;
using System.IO;
using System.Text;
class GFG {
public static void Main()
{
string path = @"file.txt" ;
using (FileStream fs = File.OpenWrite(path))
{
Byte[] info = new UTF8Encoding( true ).GetBytes( "GFG is a CS portal." );
fs.Write(info, 0, info.Length);
}
using (FileStream fs = File.OpenRead(path))
{
byte [] b = new byte [1024];
UTF8Encoding temp = new UTF8Encoding( true );
while (fs.Read(b, 0, b.Length) > 0) {
Console.WriteLine(temp.GetString(b));
}
}
}
}
|
Executing:
GFG is a CS portal.
Last Updated :
25 Feb, 2021
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