EventType.ValidateCommand

Description

Validates a special command (e.g. copy & paste).

"Copy", "Cut", "Paste", "Delete", "FrameSelected", "Duplicate", "SelectAll" and so on. Sent only in the editor.

Example: Make pasting work in current window or control:

using UnityEngine;
using UnityEditor;

public class Example : MonoBehaviour
{
    void OnGUI()
    {
        //implement frame selection
        Event e = Event.current;
        if (e.type == EventType.ValidateCommand && e.commandName == "Paste")
        {
            Debug.Log("validate paste");
            e.Use(); // without this line we won't get ExecuteCommand
        }

        if (e.type == EventType.ExecuteCommand && e.commandName == "Paste")
        {
            Debug.Log("Pasting: " + EditorGUIUtility.systemCopyBuffer);
        }
    }
}

Additional resources: EventType.ExecuteCommand, Event.commandName.