string常用方法

1、Replace string替换字符串:

string st = "abcdef";

string newstring = st.Replace('a','x');

Console.WriteLine(newstring);	//即:xbcdef

****

string st = "abcdef";

string newstring = st.Remove(4);

Console.WriteLine(newstring);  //即：abcd

string st = "abcdef";

string newstring = st.Substring(2);

Console.WriteLine(newstring);  //即：cdef

public string Substring(int startIndex,int count); 从startIndex位置开始，提取count个字符。
如：  

string st = "abcdef";

string newstring = st.Substring(2，2);

Console.WriteLine(newstring);  //即：cd

string st = "语文|数学|英语|物理";

string[] split = st.Split(new char[]{'|'},2);

for (int i = 0; i < split.Length; i++)
{
    Console.WriteLine(split[i]);
}

** **

string str="";  
1、if(str=="")  
2、if(str==String.Empty)  
3、if(str.length==0) 
if(string.IsNullOrEmpty( str )) 
if(str!=null&&str.length==0)

string str="123456";  
str.Insert(0,"x");//x123456