using System; using System.Windows.Forms; class ExampleClass : Form { [System.Security.Permissions.SecurityPermission(System.Security.Permissions.SecurityAction.Demand, Flags = System.Security.Permissions.SecurityPermissionFlag.UnmanagedCode)] protected override void WndProc(ref Message m) { // Check if message is a WM_COPYDATA message if (m.Msg == 0x4A) { // Retrieve the long parameter value from the message long lParam = m.LParam.ToInt64(); // Perform actions using the retrieved long parameter value // ... // Call the base class method for further processing of message base.WndProc(ref m); } else { // Call the base class method for processing of non-WM_COPYDATA message base.WndProc(ref m); } } }This code example demonstrates the use of System GetLParam function in a custom method called WndProc. Here, the method checks if the message is a WM_COPYDATA message and then retrieves the long parameter value from the message using System GetLParam function. The package library for System GetLParam function is part of the System DLL (Dynamic Link Library) in the C# programming language. It can be accessed through the namespace System.Windows.Forms in the System.Windows.Forms.dll, which is included in the .NET Framework.