Namespace (namespace): for problem-solving class of the same name, it can be seen as "class folder"
If the code and the class is being used in a need to use the namespace Using
In different namespaces There are two ways to call the class:
1: Write the full name of the namespace class name.
2: first using a reference space, then call
In a project to use in other projects like
Method One: Right-click the project name ---- Add Reference
Use using the project name in the code, this time in the main function can be called up to participate in class
Example: Using _01 Object-Oriented
Method Two: Write the full name of the namespace class name.
String processing:
can be seen as an array of read-only string of char, an important feature in C # string: immutability, the string can not be changed once the declaration
It can only be read by the index specified location char char can not formulate a position to make changes.
If you have to modify char, we can create a new string, you can use s.ToCharArray () method to get an array of char strings
For chestnuts to illustrate this fact:
static void Main(string[] args)
{
string text = "哈哈小杨又帅了";
text[3] = '啦';
char ch = text[2];
Console.WriteLine(ch);//显示的结果是小，说明序号是从0开始的
Console.ReadKey();
}
//这个时候如果直接给 text【3】赋值，是报错的
//所以说明了string可以看做是char的只读数组；
//想直接改变 类型为 string 类型的 text的字符串
//利用text【3】是不能实现的，因为是只读属性
可以用其他的方法将 字符串变成字符串数组：
String text="哈哈，赫于富又帅了";
Char[] chs=Text.ToCharArray();
Chs[5]='很'
String str=new String（chs）；
Console.writeline(str);
Some common methods strings:
| Method name | description |
| ToLower（） | Obtained lowercase string. |
| ToUpper（） | Get a string uppercase |
| s1.Equals（s2，stringComparison.OrdinallgnoreCase） | Compare two strings are not case sensitive It is noted that: This method needs to be received with a variable of type bool |
| s1.Split () | Remove the unwanted characters in the string
String str = "Ha ha ha -----, I have ---"; Char [] chs = new char [] { '', '-'} // not wanted inside the store String []result=str.Split(chs);
This time split () method can achieve this functionality. But this time will have blank entries, if we add: chs，StringSplitOptions.RemoveEmptyEntries
|
| .ToString() | All types can be converted to the string method call .ToString type Int num = 10; String s=num.ToString(); |
| string Replace（string OldValue，string newValue） | The local oldvalue appear in a string replacement called newvalue example: String name = "it is very rich in the rich"; Name = name.replace ( 'very', 'no'); Console.readkey(); |
| Bool Contains（string value） | Determining whether the character string contains the substring value Returns the logical value example:
Bool result = Name.Contains ( "Yang") // determines whether or not this string contains the substring If （result） { console.writeline ( "string string {0}", result) } Else { console.writeline ( "string string {0}", result) } |
| string substring(int startIndex)
|
Interception from the position startIndex start until the last string |
| bool StartsWith(String value) bool EndsWith(String value)
|
If the value at the beginning of the string is determined substring / end |
| str.indexof(strr) | Strr determine whether there is str, if there is then put back to the index of the string, if the string is not found, the result returned is -1 example: String str="abcdddaa"； Int index =Str.indexof("a",5)； The value returned 6
Start looking to find a string from an index, returns the index to find, can not find it returns -1 |
| str.Lastindexof() | 找最后一个字符串的索引 |
| str.Insert(位置，字符串) | 在str字符串的指定位置处，插入规定的字符串 |
join 方法的使用：
//把{“阿道夫”，“阿斯蒂芬”，“大”} 变成：
{“阿道夫|阿斯蒂芬|大”}
String[] names={“阿道夫”，“阿斯蒂芬”，“大”}；
String st=string.join("|",names);
Console.Writelin(st);
最终结果：
阿道夫|阿斯蒂芬|大String.isnullorempty 的用法：
返回的是逻辑值，所以需要用一个bool变量来接收
String str=“”；
Bool result =string.isNullOrEmpty(str);
If (result)
{
Console.writeline("有东西");
}
Else
{
Console.writeline("没有东西")；
}