file-readlines

C# – Read a text file line by line

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There are two simple ways to read a text file line by line: Here’s an example of using File.ReadLines() to read a file line by line in a loop: This outputs the file’s lines: Here’s an example of using File.ReadAllLines() to read the same file into a string array and then loop through it. Skip … Read more

C# – How to update a file’s contents

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There are three ways to update a file’s content: Which option you pick depends on the file’s format and size. For example, if you’re writing to an existing CSV file, you’d append new lines to the end of the file. If you’re updating a JSON file, you’d read all the JSON content, make changes, then … Read more

C# – Using CsvHelper when there’s no header row

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When you’re parsing CSV with CsvHelper and there’s no header row, you have to configure it to map by field position. I’ll show how to do that. At the end, I’ll show the alternative approach of manually parsing in this scenario. Consider the following CSV data without a header row: Normally, CsvHelper maps fields to … Read more

C# – Parsing a CSV file

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In this article, I’ll show how to parse a CSV file manually and with a parser library (CsvHelper). Let’s say you have the following CSV file: To manually parse this, read the file line by line and split each line with a comma. This gives you a string array containing the fields that you can … Read more

C# – Save a list of strings to a file

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The simplest way to save a list of strings to a file is to use File.WriteAllLines(). This creates (or overwrites) the file and writes each string on a new line. The resulting file looks like this: Note: Showing non-printable newline characters \r\n for clarity. Specifying the separator character What if you want to separate each … Read more

C# – Parsing CSV data when a field has commas

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When you have commas in your CSV fields, it creates a conflict with the field delimiting commas. In other words, you can’t tell which data belongs to which field. How you deal with this will depend on one question: is the field with the comma enclosed in quotes? Comma is enclosed in quotes Spreadsheet programs … Read more