extending method to already exist class

gistfile1.txt

public static class TransformHelper
{	
	public static Transform GetChild(this Transform self, string name)
	{
		Transform t = null;
		if(name != "") 
			t = self.Find(name);
		if(t == null) 
			t = self;
		return t;
	}

	public static Transform FindChildByName(this Transform self, string childname)
	{
		Transform found = null;
		
		if (self.name == childname)
			return self.transform;
		
		foreach (Transform child in self)
		{
			found = child.FindChildByName(childname);
			if (found)
			{
				return found;
			}
		}
		
		return null;
	}


}