C# DLL Message Box

Is it possible to have a C# DLL open a message box? Like in a WinForm:

MessageBox.Show("Message");

I relise that DLL's 开发者_如何学Ccan't be executed directly but what if it were to be injected into a process to be run, then it could show the message box (if it's possible).

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Step1: Click on Add Reference. Under .NET, Select System.Windows.Forms and click ok!

Step2: use namespace using System.Windows.Forms;