Migrated the project to dotnet core 3.0

src/NotifyIconWpf/Interop/WindowClass.cs

@@ -0,0 +1,35 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Hardcodet.Wpf.TaskbarNotification.Interop
+{
+    /// <summary>
+    /// Callback delegate which is used by the Windows API to
+    /// submit window messages.
+    /// </summary>
+    public delegate IntPtr WindowProcedureHandler(IntPtr hWnd, uint uMsg, IntPtr wParam, IntPtr lParam);
+
+
+    /// <summary>
+    /// Win API WNDCLASS struct - represents a single window.
+    /// Used to receive window messages.
+    /// </summary>
+    [StructLayout(LayoutKind.Sequential)]
+    public struct WindowClass
+    {
+        #pragma warning disable 1591
+
+        public uint style;
+        public WindowProcedureHandler lpfnWndProc;
+        public int cbClsExtra;
+        public int cbWndExtra;
+        public IntPtr hInstance;
+        public IntPtr hIcon;
+        public IntPtr hCursor;
+        public IntPtr hbrBackground;
+        [MarshalAs(UnmanagedType.LPWStr)] public string lpszMenuName;
+        [MarshalAs(UnmanagedType.LPWStr)] public string lpszClassName;
+
+        #pragma warning restore 1591
+    }
+}