Debug error with text files

Hi.I am trying to write the below program. but error is coming . Also when i debug i am getting the error message like "could not copy....." as shown in the snapshot attached. This error comes frequently for any other programs also. why is it so?

 

//Write  simple program that counts how many times a substring(C#) occurs in a text file.

//This is our "Intro to Programming in C#" book.In it you will learn the basics of C# programming.You will find out how nice C# is.

StreamWriter writing = new StreamWriter(@"C:\Users\harish\Desktop\C Sharp\Practice\TextFiles\Occurences\Occurences.txt");

int count = 0;

if (File.Exists(@"C:\Users\harish\Desktop\C Sharp\Practice\TextFiles\Occurences\Occurences.txt"))

{

writing.Write("This is our Intro to Programming in C# book.In it you will learn the basics of C# programming.You will find out how nice C# is");

writing.Close();

StreamReader reading = new StreamReader(@"C:\Users\harish\Desktop\C Sharp\Practice\TextFiles\Occurences\Occurences.txt");

Console.WriteLine(reading.ReadLine());

string array = reading.ReadLine().Substring(0, 50);

for (int i = 0; i < array.Length; i++)

{

if (array[i] == 'C' && array[i + 1] == '#')

{

count++;

}

} Console.WriteLine(count);

reading.Close();

}