develop Notepad++ plugins (in c#).

Notepad++ is awesome and you should be too, by developing plugins for it. To do so:
1) Go to notepad++ website, resource section (at least it was called it so back in 2020).
2) Find section about developing plugins, and options for other languages, select your language of choice.
3) Find “visual studio project template” zip archive, download it and copy it under your documents/Visual Studio 20xx/Project Templates
4) Open VS, create new project and search for “Notepad++” project template, it will create you nice “Hello plugin” sample.
Note: It might not showup. If everything fails, just search for example projects on same plugin page and use it as a template for your project.

useful sample to cover most needs

IntPtr currentScint = PluginBase.GetCurrentScintilla();
ScintillaGateway scintillaGateway = new ScintillaGateway(currentScint);

int numLines = scintillaGateway.GetLineCount(); 
StringBuilder endResult = new StringBuilder();
for (int lineIndex = 0; lineIndex < numLines; lineIndex += 1)
{                   
   string sourceData = scintillaGateway.GetLine(lineIndex);
   endResult.AppendLine(DoMyTransform(sourceData));
}
scintillaGateway.SetText(endResult.ToString());