Util.cs

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public static class Util
{ 
	public static T GetChildByName<T>(this GameObject go, string name) where T:Component
	{
		var child = GetChildByName(go, name);
		if (child == null)
			return default(T);

		return child.gameObject.GetComponent<T>();
	}

	public static GameObject GetChildByName(this GameObject go, string name) 
	{
		var child = GetChildByName(go.transform, name);
		return child == null ? null : child.gameObject;
	}

    public static Transform GetChildByName(Transform tr, string name)
    {
		// 广度优先
        foreach (Transform child in tr)
        {
            if (child.name == name)
                return child;
        }

		foreach (Transform child in tr)
		{
			Transform c = GetChildByName(child, name);
			if (c != null)
				return c;
		}

        return null;
    }

	public delegate bool TraversalCallback(Transform go);
	public static bool Traversal(this Transform transform, TraversalCallback callback)
	{
		// 深度优先
		foreach (Transform child in transform)
		{
			if (!callback(child))
				return false;

			if (!child.Traversal(callback))
				return false;
		}
		return true;
	}

    public static void ChangeLayer(GameObject go, int layer)
    {
        go.layer = layer;
		go.transform.Traversal(child=>{child.gameObject.layer = layer; return true; });
    }
	
	public static string UrlToIP(string url)
	{
		try
		{
            var host = System.Net.Dns.GetHostEntry(url);
            foreach (System.Net.IPAddress ip in host.AddressList)
            {
                if (ip.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork)
                    return ip.ToString();
            }
            return url;
		}
		catch(System.Exception e)
		{
			Debug.LogException(e);
			return url;
		}
	}

    public static string Md5File(string file)
    {
        using (var stream = System.IO.File.OpenRead(file))
        {
            var md5 = System.Security.Cryptography.MD5.Create();
            var data = md5.ComputeHash(stream);
            var sb = new System.Text.StringBuilder();

            foreach(var b in data)
            {
                sb.Append(b.ToString("x2"));
            }
            return sb.ToString().ToLower();
        }
    }
}