C# RichTextBox Line-by-line scan

Hey Im creating my own coding language and I already have the entire application set up with save, open, close, new, etc.

In order for the "Run" part to work, I need a way to scan and test every single line in richTextBox1.

Maybe for past Java users, something along the lines of the "java-util-scanner," but easier to use for testing each line.

Does anyone know a way to do this, where a string "scannedString" would be tested as so:

if(scannedString == "#load(moduleFiles)") {
    //action here
}
string scannedStringNextLine = ???
if(scannedStringNextLine = "") {
    //action here
}

Eventually it would look more like this:

if(scannedString == "code1" || scannedString == "code2" etc... ) {
    if(scannedString == "code1") {
        //action here
    }
} else {
    //error message
}

hope this is enough information...