Reading and Writing Files using StreamReader in C#

Reading and writing files is an important for any program. C# has provided many classes to perform operations on Files.
Below is the Program showing use of StreamReader and StreamWriter to write the Characters in the Files.

using System;
using System.IO;
using static System.Console;
namespace StreamDemo
{
class Program
{
static string line="";
static void Main(string[] args)
{
StreamWriter st = new StreamWriter("D:\\Test.txt",true);
string [] cars = { "Audi", "Jeep","Jaguar" };
foreach(string s in cars)
{
st.WriteLine(s);
}
st.Close();
StreamReader sr = new StreamReader("D:\\Test.txt");
while ((line = sr.ReadLine()) != null)
{
WriteLine(line);
}
sr.Close(); ReadLine();
}
}
}

Output

Explanation

Above Program writes the array of cars in the File character by character.

StreamReader and StreamWriter performs the operations on files character by characters.

We initialized the object of StreamWriter class and gave the path where the file is to be created.

If the files with the same name is already present there at the path, StreamWriter opens that file.

If the file at the given path has already some text , and the append property is set to true, the StreamWriter class will append the text at the end of existing text.

using foreach loop , we write the array of string is the file.

Then we close the connection of the StreamWriter to the file

Closing the open connection is necessary , otherwise you will not able to access that file with StreamReader. It will throw an error that file is already in use.

Then using the StreamReader object , we access that file.

Using While loop we read the containts of the file and display it on the console.

Let's do the same program in different way.

using System;
using System.IO;
using static System.Console;
namespace FileApplication
{
class Program
{
static void Main(string[] args)
{
string[] names = new string[5];
WriteLine("Enter names of fruits");
for (int i = 0; i < names.Length; i++)
{
names[i] = ReadLine();
}
using (StreamWriter sw = new StreamWriter("D:\\names2.txt"))
{
WriteLine("Fruit names are below");
foreach (string s in names)
{
sw.WriteLine(s);
}
}
// Read and show each line from the file.
string line = "";
using (StreamReader sr = new StreamReader("D:\\names2.txt"))
{
while ((line = sr.ReadLine()) != null)
{
WriteLine(line);
}
}
ReadKey();
}
}
}

Output

Explanation

In above program , we are taking user input in the array of strings and writing in the file at the given path.

We have not specified if the append is true or false, so by default it is false.

Here we have used the statement using so that the connection is automatically close with the close of using statement.

the program ask user for name 5 fruits and writes in the file and also displays on the console.