Question

I am firing up Visual C# (2010 Express) for the first time, and I’ve created a new project for a WindowsFormsApplication. No code has been written yet, but I created a button and placed it on Form1. Then, I double-clicked the button and am taken to the part of the code where you write what happens when the button is push/clicked.

The first thing I would like to do is read data from a LARGE tab-delimited text file (30MB). The text file contains 7 structured columns of data like names, age, favorite color, animal, etc. Nothing tricky or fancy in the text formatting. I’m using the code below:

File.ReadLines(sourceFilePath)
.Select(line => line.Split('\t'))
.ToArray();

But my more basic question is how do I establish and define File and sourceFilePath? With the code above I get “The name ‘File’ does not exist in the current context.

Answer 1

You need to add the following line to the top of your C# file:

using System.IO;

This will allow the use of the File class, which is in the System.IO namespace.

As for defining sourceFilePath, that’s just a variable, which you can declare and set to whatever file path you need, e.g.

string sourceFilePath = @"c:\data\file.csv";

Note the use of @ before the string literal; this prevents the backslashes from being treated as the start of escape sequences. You can instead just escape the bakslashes, e.g.

string sourceFilePath = "c:\\data\\file.csv";