I’m sure it’s another C# stupidity, right?
Apart from the fact that I’m still a beginner in this language, I don’t understand foreach very well.

public static void test ()
{
    string str = "";

    foreach (string line in str)
    {
        Console.WriteLine(line);
    }
}

using the var keyword, that’s not what I want
I need to check string, and this is for file

CS0030: Cannot convert type 'char' to 'string'

I ask myself: why char??
btw, this is my code.
I’m doing this to try to detect lines in a .txt file

public static readonly string file_name = "medallion.txt"; 
public static void file ()
{
    var file = File.OpenWrite(file_name);  // open the txt file

    foreach (string line in File.ReadAllText(file_name))
    {
        if (line == string.Empty || line.StartsWith("//")) continue;  // trrying to do comments
    }
}

CS0030: Cannot convert type 'char' to 'string'