C#-Why does this if statment removes a new line character on StreamReader's output?

Question

StreamReader reader = new StreamReader("randomTextFile.txt");
string line = "";

while (line != null)
{
    line = reader.ReadLine();

    if (line != null)
    {
        Console.WriteLine(line);
    }
}

reader.Close();
Console.ReadLine();

In the above code, there is an if statment inside the while statment, even though they specify the same thing (line != null). If I remove said if statment, a new line will be added after the txt file contents (instead of "11037", the console will show "11037" + an empty line).

Answer 1

The while-loop exit condition will only be checked when it is invoked, so at the beginning of each iteration, not everytime inside it's scope.

MSND: the test of the while expression takes place before each execution of the loop

You could use this loop:

string line;
using (var reader = new StreamReader("randomTextFile.txt"))
{
    while ((line = reader.ReadLine()) != null)
    {
        Console.WriteLine(line);
    }
}

You should also use the using-statement as shown above on every object implementing IDisposable. On that way it is ensured that unmanaged resources are disposed.

---

According to the Console.WriteLine specific question why it writes a new line even if the value is null, that's documented:

If value is null, only the line terminator is written to the standard output stream.