How to Read from a Text File in C#? -- C# -- System.IO.StreamReader

 How to Read from a Text File in C#? -- C# -- System.IO.StreamReader 


[Ans]

using System.IO.StreamReader()

[Syntax] 

StreamReader StreamReader(string fileName);
where fileName is the name of file that you read

[NOTE]

Great Importance!!! Please pay a lot attention!!!


(1)
Compiler reads file under subfiolder of the path \bin\Debug\netcoreapp3.1 in your project.
When you use StreamReader, the argument will be given as 
<yourProject>\bin\Debug\netcoreapp3.1\<fileName>

e.g.
When I create a new C# project with project name StreamReader_All in the path C:\Users\jayw7\OneDrive\桌面\CSharp\StreamReader .
I should write
 C:\Users\jayw7\OneDrive\桌面\CSharp\StreamReader\StreamReader_All\StreamReader_All\bin\Debug\netcoreapp3.1

(2)
In C#, "\" means escape character.
If you would like to present a directory, you must use "\\" instead of "\" or  add "@" before your directory.

How to read all lines from text file in C#?

step1:
read file from text file with StreamReader().
step2:
read a line from StreamReader with ReadToEnd() method.
example code:
using (StreamReader sr=new StreamReader("Invoke_InvokeRepeating.txt"))
{
               string s = "";
               s = sr.ReadToEnd();
                Console.WriteLine(s);
}


How to read a line from text file in C#?

step1:
read file from text file with StreamReader().
step2:
read a line from StreamReader with ReadLine() method.


example code:
 using (StreamReader sr=new StreamReader("Invoke_InvokeRepeating.txt"))
 {
               string line = "";
               line = sr.ReadLine();
                int index = 1;
               while(line!=null)
               {
                    Console.WriteLine(index + "th line:" +line);
                    index += 1;
                    line = sr.ReadLine();
               }
 }
  

[Useful Tips]

I recommend you that  close the  StreamReader after using it.
And When StreamReader is declared in using keyword, system will automatically close it after using block ending.




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