AssetFilesCounter.cs

using UnityEngine;
using UnityEditor;
using System.Collections;
using System.Collections.Generic;
using System.IO;

public static class AssetFilesCounter
{
	[MenuItem("Utilities/Count Asset Files")]
	public static void CountAssetFiles()
	{
		EditorUtility.DisplayProgressBar("Counting Asset Files", "", 0);
		
		try
		{
			// using our own counting here, AssetDatabase.GetAllAssetPaths() would include directories
			int assetFilesCount = GetAllFilesExcludingExtensions(Application.dataPath, "*.*", "meta").Length;

			Debug.Log("Asset Files: " + assetFilesCount);
		}
		finally
		{
			EditorUtility.ClearProgressBar();
		}
	}

	public static string[] GetAllFilesExcludingExtensions(string path, string searchPattern, params string[] extensions)
	{
		if (!Directory.Exists(path))
		{
			throw new DirectoryNotFoundException("Directory " + path + " not found.");
		}

		// make sure extension has the right format
		for (int i = 0; i < extensions.Length; i++)
		{
			if (!extensions[i].StartsWith("."))
			{
				extensions[i] = "." + extensions[i];
			}
		}

		var allFiles = Directory.GetFiles(path, searchPattern, SearchOption.AllDirectories);

		List<string> validFiles = new List<string>();

		foreach (var file in allFiles)
		{
			if (!PathHasExtension(file, extensions))
			{
				validFiles.Add(file);
			}
		}

		return validFiles.ToArray();
	}

	public static bool PathHasExtension(string path, params string[] extensions)
	{
		for (int i = 0; i < extensions.Length; i++)
		{
			if (path.EndsWith(extensions[i]))
			{
				return true;
			}
		}

		return false;
	}
}