File

AppendAllLines	Opens a file and appends lines to the end of the file and closes the file.
AppendAllLinesAsync	Asychronously opens a file and appends lines to the end of the file and closes the file.
AppendAllText	Opens a file and appends a string to the end of the file and then closes the file.
AppendAllTextAsync	Asychronously opens a file and appends a string to the end of the file and then closes the file.
AppendText	Opens a text file in append mode returning a StreamWriter object
Copy	Copies a file to a new destination
Create	Creates and opens a file returning a FileStream object
CreateText	Creates a text file returning a StreamWriter object
Delete	Deletes a file
Exists	Returns True if the file exists
GetAttributes	Returns the attributes of a file
GetCreationTime	Returns the creation time of the file
GetLastAccessTime	Returns the last access time of the file
GetLastWriteTime	Returns the last write time of a file
Move	Moves a file
Open	Opens a file with a specified mode, access and share returning a FileStream object
OpenRead	Opens a file in read mode returning a FileStream object
OpenText	Opens a text file for reading returning a StreamReader object
OpenWrite	Opens a file in write mode returning a FileStream object
ReadAllBytes	Opens a binary file and reads the contents into a byte array and then closes the file.
ReadAllBytesAsync	Aschronously opens a binary file and reads the contents into a byte array and then closes the file.
ReadAllLines	Opens a text file and reads all the lines of the file and then closes the file.
ReadAllLinesAsync	Asynchronously opens a text file and reads all the lines of the file and then closes the file.
ReadAllText	Opens a text file and reads all the text in the file and then closes the file.
ReadAllTextAsync	Asynchronously opens a text file and reads all the text in the file and closes the file.
ReadLines	Reads all the lines of a file.
Replace	Replaces the contents os a specified file with the contents of another file, deleting the original file and creating a backup of the replaced file.
SetAttributes	Sets the attributes for a file
SetCreatiionTime	Sets the creation time of the file
SetLastAccessTime	Sets the last access time of the file
SetLastWriteTime	Sets the last write time of the file

Open

Opens a file with a specified mode, access and share returning a FileStream object
The sharing mode lets you control whether or not other processes can read from or write to the file while you have it open.
A lot of the arguments correspond to overloads of the FileStream constructor.
This method gives you greater (than the Create, OpenRead and OpenWrite methods) when creating new files.
If you want total control when opening and creating files then you should use the FileStream constructor.

System.IO.File.Open(file [,mode [,access [,share ]]]) 
System.IO.File.Open("C:\temp\file1.txt", _ 
                    FileMode.Append | Create | CreateNew | Open | OpenOrCreate | Truncate, _ 
                    FileAccess.Read | Write | ReadWrite, _ 
                    FileShare.None | ReadWrite | Read | Write | Inheritable

OpenRead

Opens an existing file in read mode returning a FileStream object
The file is opened using the default sharing mode
The FileStream is positioned at the beginning of the file.

System.IO.File.OpenRead(file)

System.IO.FileStream oFileStream; 
oFileStream = System.IO.File.OpenRead("C:\Temp\textfile.txt");

OpenWrite

Opens a file in write mode returning a FileStream object
Any existing data in the file will be overwritten.
If the file you are trying to open does not exist then it will be created.

System.IO.File.OpenWrite(file);

OpenText

Opens a text file for reading returning a StreamReader object
This method returns a StreamReader that is positioned at the beginning of the file.

System.IO.File.OpenText(file);

CreateText

Creates a text file and opens it for reading. This returns a StreamWriter object.
If the file you want to create already exists then it is overwritten.

System.IO.File.CreateText(file);

AppendText

This method can be used if you want to append data to a text file.
Opens an existing text file in append mode returning a StreamWriter object
If the file you want to open does not exist then a new file is created.

System.IO.File.AppendText(file);

Copy

Copies a file from one location to another.
This method will fail if the file already exists and you have not explicitly stated to overwrite the file.
You also have the option to overwrite the file it it already exists.

System.IO.File.Copy(source, dest [,overwrite]); 
System.IO.File.Copy("file1.txt","file2.txt",false); 
System.IO.File.Copy("file1.txt","file2.txt",true);

Delete

Deletes an existing file
This method will throw an exception if the file is in use or if you do not have access (or permission) to delete it.
It will not throw an exception if the file does not exist.

System.IO.File.Delete(path);

GetCreationTime

Returns a DateTime telling you when the file was created.

System.IO.File.GetCreationTime(path);

SetCreatiionTime

System.IO.File.SetCreatiionTime(path, datetime);

GetLastAccessTime

System.IO.File.GetLastAccessTime(path);

SetLastAccessTime

System.IO.File.SetLastAccessTime(path, datetime);

GetLastWriteTime

System.IO.File.GetLastWriteTime(path);

SetLastWriteTime

System.IO.File.SetLastWriteTime(path, datetime);