Writing text files in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the simplest way to write text to a file in C#?

Use File.WriteAllText(path, content) to write a string directly to a file. It creates the file if it doesn't exist or overwrites it if it does.

beginner

How do you append text to an existing file in C#?

Use File.AppendAllText(path, content) to add text at the end of the file without deleting existing content.

beginner

What namespace must you include to work with file writing in C#?

Include using System.IO; to access file writing classes and methods like File.

intermediate

How can you write multiple lines to a file efficiently?

Use File.WriteAllLines(path, string[] lines) to write an array of strings, each as a new line in the file.

intermediate

What happens if the file path does not exist when writing a file?

If the directory path does not exist, File.WriteAllText throws an exception. You must create directories first using Directory.CreateDirectory.

Which method overwrites the entire file content when writing text in C#?

A File.WriteAllLines

B File.AppendAllText

C File.WriteAllText

D File.ReadAllText

File.WriteAllText replaces the whole file content with new text.

What does File.AppendAllText do?

A Deletes the file

B Adds text to the end of the file

C Reads text from the file

D Creates a new empty file

It adds new text at the end without removing existing content.

Which namespace is required to use File.WriteAllText?

A System.IO

B System.Net

C System.Text

D System.Threading

System.IO contains file handling classes.

How do you write multiple lines to a file at once?

A File.ReadAllLines

B File.AppendAllText with newline characters

C File.WriteAllText with newline characters

D File.WriteAllLines with a string array

File.WriteAllLines writes each string in an array as a separate line.

What must you do if the directory does not exist before writing a file?

A Use Directory.CreateDirectory to create it

B Nothing, it creates automatically

C Use File.Delete first

D Use File.ReadAllText

You must create the directory first or writing will fail.

Explain how to write text to a file in C# and what happens if the file already exists.

Think about the simplest method to write text and its behavior with existing files.

Describe how to safely write text to a file when the directory might not exist.

Consider what happens if the folder path is missing.