Copying information from web page

Question

Firstly, I would like to state that I am a newbie at coding C# so if something is not possible please tell me.
Okay so I have been trying to open web pages and copy all the text from it and write it to a text file.
I have got the writing to text file bit, but I want to know if it is possible to copy all the text from a web page into a variable.
If it is possible is it quite difficult or relatively simple? If simple could you please give me an idea about how I would go about achieving this. 
If it is any help, I am opening the web page by the following code:

Process proc = new Process();

            proc.StartInfo.UseShellExecute = true;

            proc.StartInfo.FileName = "";

            proc.Start();