System.IO.StreamReader

You use a StreamReader object to read from a text file.
There are a number of ways you can obtain the StreamReader object
The fifth line, lets the system decide the best type of encoding

System.IO.StreamReader oStreamReader; 
oStreamReader = new System.IO.StreamReader(@"C:\\Temp\\textfile.txt"); 
oStreamReader = new System.IO.StreamReader(@"C:\\Temp\\textfile.txt", System.Text.Encoding.ASCII); 
oStreamReader = new System.IO.StreamReader(@"C:\\Temp\\textfile.txt", System.Text.Encoding.Unicode); 
oStreamReader = new System.IO.StreamReader(@"C:\\Temp\\textfile.txt", true); 

Using a FileStream

System.IO.StreamReader oStreamReader; 
System.IO.FileStream oFileStream; 
oFileStream = new System.IO.FileStream(@"C:\\Temp\\textfile.txt", FileMode.Open); 
oStreamReader = new System.IO.StreamReader(objFileStream); 

Using a Stream
This lets you specify the mode, access and share

System.IO.StreamReader oStreamReader; 
System.IO.Stream oStream; 
oStream = System.IO.File.Open(@"C:\\Temp\\textfile.txt", FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite); 
oStreamReader = new System.IO.StreamReader(oStream, System.Text.Encoding.UTF8); 

Using a FileInfo

System.IO.StreamReader oStreamReader; 
System.IO.FileInfo oFileInfo; 
oFileInfo = new System.IO.FileInfo(@"C:\\Temp\\textfile.txt"); 
oStreamReader = objFileInfo.OpenText 

Using File.OpenText

System.IO.StreamReader oStreamReader; 
oStreamReader = System.IO.File.OpenText(@"C:\\Temp\\textfile.txt"); 

Reading the Contents

There are several ways to read from a StreamReader

ReadToEndAsyn

This can also be used to read all the remaining characters.

string sWholeFile; 

// async 
using (oStreamReader) 
{ 
   sWholeFile = await oStreamReader.ReadToEndAsync(); 
} 
// sync 
sWholeFile = objStreamReader.ReadToEnd; 

ReadToEnd

ReadLine

string sLine; 
string s = String.Empty; 

while( (s = oStreamReader.ReadLine() ) != null); 
{ 
} 

Read

Read a Single Character

string sCharacter; 
sCharacter = objStreamReader.Read; 

Peek

The Peek method actually returns the code of the next character in the stream without actually extracting it, or it returns -1 if there are no more characters.
This method is used to test for the end of the file.

while (oStreamReader.Peek = -1) 
{ 
read the stream 
}