【C#】知识点漫谈1019

C#异常

var ae = new ArgumentException();// 参数异常
var ane = new ArgumentNullException();// 参数为空异常
var aore = new ArgumentOutOfRangeException();// 参数超出范围异常
var dne = new DirectoryNotFoundException(); // 文件路径没有找到
var fne = new FileNotFoundException(); //文件没有找到异常
var ioe  =  new InvalidOperationException(); //非法运算符的异常
var nie = new NotImplementedException();//没有实现的异常

C#的I/O操作

打开文件的操作
1、File.Exists
2、Directory.Exists
3、string path=" “;
DirectoryInfo dir = new DirectoryInfo(path);
FileInfo[] files = dir.GetFiles(”*.exe");
写入文件的操作
不存在文件，创建文件写入数据

private const string FILE_NAME = "Test.txt";
static void Main(string[] args)
{
	if(File.Exists(FILE_NAME))
	{
		Console.WriteLine("{0} already exists!",FILE_NAME);
		Console.ReadLine();
		return;
	}
	FileStream fs = new FileStream(FILE_NAME ,FileMode.Create);
	BinaryWriter w = new BinaryWriter(fs);
	for(int i=0;i<11;i++)
	{
		w.Write("a");
	}
	w.Close();
	fs.Close();
}

5、存在文件，读取文件

private const string FILE_NAME ="Test.txt";
static void Main(string[] args)
{
	if(!File.Exists(FILE_NAME))
	{
		Console.WriteLine("{0} does not exist!",FILE_NAME);
		Console.ReadLine();
		return;
	}
	FileStream fs = new FileStream(FILE_NAME,FileMode.Open,FileAccess.Read);
	BinaryReader r = new BinaryReader(fs);
	for(int i = 0; i<11 ; i++)
	{
		Console.WriteLine(r.ReadString());
	}
	r.Close();
	fs.Close();
	Console.ReadLine();
}

6、读文件

private const string FILE_NAME ="Test.txt";
static void Main(string[] args)
{
	if(!File.Exists(FILE_NAME))
	{
		Console.WriteLine("{0} does not exist!",FILE_NAME);
		Console.ReadLine();
		return;
	}
	using (StreamReader sr = File.OpenText(FILE_NAME))
	{
		string input;
		while((input = sr.ReadLine())!=null)
		{
			Console.WriteLine("The end of the steam");
			sr.Close();
		}
	}
	Console.ReadLine();
}

C#的Attribute

1、[Conditional(“DEBUG”)]
2、[Obsolete(“Don’t use old Method!”,true)]弃用了方法

[AttributeUsage(AttributeTargets.Class,AllowMultiple=false,Inherited=false)]
public class HelpAttribute : Attribute
{
        protected string description;
        public HelpAttribute(string description_in)
        {
            this.description = description_in;
        }
        public string Description
        {
            get
            {
                return this.description;
            }
        }
        public string Name
        {
            get;
            set;
        }
}
//value type,System.Type 
[Help("this is a do-nothing class",Name="极客学院")]
public class AnyClass
{ 
}

通过反射来获取Attribute中的信息

[Attribute]

static void Main(string[] args)
        {
            HelpAttribute helpAttribute;
            foreach (var attr in typeof(AnyClass).GetCustomAttributes(true))
            {
                helpAttribute = attr as HelpAttribute;
                if (null != helpAttribute)
                {
                    Console.WriteLine("AnyClass Description:{0}", helpAttribute.Description);
                    Console.WriteLine(helpAttribute.Name);
                }
            }
        }

C#反射

static void Main(string[] args)
{
		string s = "Hello Reflection";
		Type t = s.GetType();   //直接获取类型
		Console.WriteLine(t.FullName);
		Type t2 = Type.GetType("System.String",false,true);   // 静态方法获取类型
		Console.WriteLine(t2.FullName);
		Type t3 = typeof(string);  //
		Console.WriteLine(t3.FullName);
		Console.ReadLine();
}

反射获取方法
MethodInfo[ ] mi = t.GetMethods(BindingFlags.Public|BindingFlags.Instance);
反射获取字段
GetFileds()、GetProperites()

C#中动态加载以及推迟绑定

Assembly objAssembly = Assembly.GetExecutingAssembly();
Type t = objAssembly.GetType("反射实现动态加载.Car", false, true);
object obj = Activator.CreateInstance(t);
MethodInfo mi = t.GetMethod("IsMoving");
var isMoving = (bool)mi.Invoke(obj, null);

运行时创建新的类，然后动态加载进来
//System.Emit