Integerate Dll in software c#

I'm guessing you want to distribut eyour application as single .exe and load all dlls from embedded resource.

If that's the case you need to:
1) add dll to the project (Project/Add Existing Item..)
2) change added dll properties:
• BuildAction = embedded Resource
• Copy To Output Directory = Do not copy

Then in your code you need to code AppDomain.CurrentDomain.AssemblyResolve event handler (this will be called whenever assembly needs to be loaded).
In the handler you need to load assembly from resources:

var stream = Assembly.GetExecutingAssembly().GetManifestResourceStream(resourcename);
byte[] assemblyData = stream.Read(assemblyData, 0, assemblyData.Length);
return Assembly.Load(assemblyData).