Check out example codes for "write text files with C#". It will help you in understanding the concepts better.

Code Example 1

// Create a file to write to.
string createText = "Hello and Welcome" + Environment.NewLine;
File.WriteAllText(path, createText);

...

// Open the file to read from.
string readText = File.ReadAllText(path);

Learn ReactJs, React Native from akashmittal.com