C# copy embedded DLL to User Folder

Question

I have a C# WinForms Application that will need to copy an embedded DLL file to the user's directory. I cannot get my application to recognize the embedded DLL file. Can Someone help?

The system keeps throwing the exception argument "eContactAutoCAD.dll does not exist" - so obviously the variable is null.

What do I need to change in order for the system to recognize the embedded file?

namespace eContact_AutoCAD_Installer
{
  public partial class Form1 : Form
  {
    public Form1()
    {
        InitializeComponent();
    }        
    
    const string dllFolder = @"C:\eContact\";
    const string dllFile = @"C:\eContact\eContactAutoCAD.dll";
    const string EMBED_DLLFILE = "eContact_AutoCAD_Installer.Files.eContactAutoCAD.dll";

   /*
     ---
   */
    
    //Copy DLL to User's "C:/eContact/" folder
    private static void copyDLL()
    {
        if (!Directory.Exists(dllFolder))
        {
            Directory.CreateDirectory(dllFolder);
        }
        try
        {


            using (Stream resource = Assembly.GetExecutingAssembly().GetManifestResourceStream(EMBED_DLLFILE))
            {
                if (resource == null)
                {
                    throw new ArgumentException("eContactAutoCAD.dll does not exist");
                }
                using (Stream output = File.OpenWrite(dllFile))
                {
                    resource.CopyTo(output);
                }
            }
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message, "ERROR", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
        }
    }

   /*
     ---
   */
  }
}

Answer 1

This example code should cover the main issues.

When adding the file, set it to Embedded Resource so the file is included in the final exe:

When accessing the resource, include the namespace and folder that contains the file. Also use a MemoryStream to access the file since it's binary data.

private int copyDLL()
{
    var resourceName = "WinFormsApp2.Files.SomeFile.dll";   // resource starts with namespace, then folder name
    MemoryStream ms = new MemoryStream();   // buffer for file bytes
    using (Stream stream = Assembly.GetExecutingAssembly().GetManifestResourceStream(resourceName))  // open resource
    {
        stream.CopyTo(ms);   // copy to buffer
        byte[] bb = ms.ToArray();   // need array to save
        File.WriteAllBytes(@"C:\tmp\SomeFile2.dll", bb);   // save byte array to file
        return bb.Length;  // return file size
    }
}