String.IsNullorEmpty()方法的使用

就上个代码而已，稍微修改了下MSDN的例子。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace StringIsNull
{
    public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            string s1 = "abcd";
            string s2 = "";
            string s3 = null;
            string s4 = " ";

            Response.Write(string.Format("String s1 {0}.", Test(s1)) + "<br />");
            Response.Write(string.Format("String s2 {0}.", Test(s2)) + "<br />");
            Response.Write(string.Format("String s3 {0}.", Test(s3)) + "<br />");
            Response.Write(string.Format("String s4 {0}.", Test(s4)) + "<br />");
        }
        public static String Test(string s)
        {
            if (String.IsNullOrEmpty(s))
            {
                return "is null or empty";
            }
            else if(String.IsNullOrEmpty(s.Trim()))
            {
                return "its Trim is null or empty";
            }
            else
            {
                return String.Format("(\"{0}\") is not null or empty", s);
            }

            

         
            
        }
    }
}