1, enumerate: the essence is the class
if for the first enumeration assign an int value, then the back of the enumeration in ascending order of
enumeration can be converted to int strong values he represents
the C # enumerations are constants ( IL can see the literal source) with Reflector
because an int value has a corresponding enumeration, so Switch int see him as
not define methods, properties, events
plurality enumeration has the same value, when the value strong turn, returns the last of enumeration
2, IEnumerable interfaces
as long as implements this interface, you can use foreach to traverse. foreach loop essence is to call this interface to return an iterator, call the iterator's MoveNext () method can achieve the cycle.
Source:
Copy the code
{
the IEnumerator the GetEnumerator (); // returns an iterator
}
public interface the IEnumerator
{
BOOL the MoveNext ();
Object Current {GET;}
void the Reset ();
}
copy the code
above is easy to see:
IEnumerable interface including GetEnumerable process (acquisition iterator object), MoveNext method (check for the next cycle element), GetCurrent process (recycled to obtain the current element)
3, a collection of
basic concepts
set is a container can hold a bunch of things. It is divided into a set of non-generic and generic collection
ArrayList-- which real data is stored in a Object [] array, which corresponds to a generic List <T>
HashTable-- non-generic set of key-value pairs, which corresponds to a generic Dictionary <TKey, TValue>
Dynamic arrays and differences, advantages and disadvantages generic collections:
Dynamic arrays do not have any constraints on the elements you want to add anything. The fundamental reason is because it is an internal data storage array of type Object.
With generic element type is the set of constraints (there is a constraint on the inside of the added element)
Generic collection to avoid packing, unboxing performance cost, while adding elements to be checked Parameter Type
Common methods
add (), AddRange (), Insert (), InsertRange (), remove (), removeAt ()
Reverse () - reversing the elements in the collection
4, the hash table
internal mechanisms:
the HashTable, a set of key-value pairs, which is an array of structures internal bucket []. There are three things: keys, values, key hash code
Data stored in the main: private bucket [] buckets;
struct bucket Private
{
public Object Key;
public Object Val;
public int hash_coll;
}
access operation:
Principle storage: the index value is calculated according to the key of the hash. When we element to the HashTable Add, the elements stored in the array index where the HashTable is calculated based on the hash value added Key (but because hash value modulo the length of the array, it certainly does not exceed the current length of the array) .
Each object counted out Hashcode not unique. There may be more of the same objects HashCode. Settlement Mechanism:
a, once again hash
B, bottled mode, two identical objects hashcode uniform loading position
c, when new, HashTable in an array of container is full, places twice the expansion of the array
Value principle: When we take elements from the HashTable where (according to key to take), according to the hash value of the index will be calculated to take the key elements and compare hash values of the elements in the key and the key parameters of the currently looking for equality, but also to compare the two key references are the same. If you are satisfied, it is determined to find the elements to be taken.
5, generic collection
referenced namespaces: System.Collections.Generic
List <T> - T is the type of storage
Dictionary<K,V>
. 6, List <T> and ArrayList performance comparison
ArrayList stored boxed value types need conjecture, stored reference type requires conversion type, and List <T> obviously not need these extra cost, high performance apparent
7, using try block time
network operation (socket), file operation (IO related), database operations, division operation (time division by zero), cast operation
8, Windows Form program documents
designer.cs design classes and reception classes is the relationship between two brothers class (partial)
9, Path class
ChangeExtension (suffix modify the file, "Edit" to support the string level, not really renaming files)
Combine-- the two paths into one path of the automatic processing path [separators]
GetDirectoryName-- get the file path name
GetExtension-- get the file extension
GetFileName-- get file path of the file name
GetFileNameWithoutExtension-- obtain the removal of the file name extension
GetFullPath-- get the full path to the file, you can get the absolute path of the relative path
GetTempFileName-- get a unique temporary file name
GetTempPath-- get the temporary folder path
…………
10, operating folders, directories
Delete-- delete directories recursively delete [] indicates whether recursive
Exists-- determine whether a directory exists
move-- move
GetDirectories + get subdirectories under a directory
GetFiles-- get the files in a directory
…………
11, the operation file
File-- manipulating files, static classes, the overall operation of the document. Copy, delete. Shear
AppendAllText-- text contents will be appended to the file path in the [If the file does not exist, create]
Exists-- determine whether there is a file path
ReadAllLines-- read a text file into a string array
ReadAllText-- read a text file into a string
WriteAllText-- Save the text contents to a file path, it overwrites the old contents
Copy-- file copy [true means that when the file exists "cover", if not true, the reported abnormal when file exists]
Create a file Create--
Delete-- If the file does not exist error
DirectoryInfo-- a folder "class" is used to describe a folder object
GetParent-- get the parent directory directory
FileInfo-- folder, a folder object to describe
requires attention:
Gets the path of the current exe file executed by Assembly.GetExecutingAssembly (). Location, do not use Directory.GetCurrentDirectory (), because the program is to obtain the current working directory, the path may become
Modify text of the coding obtained by encoding GetEncoding
12, the file stream
FileStream-- any type
StreamWriter-- write string
StreamReader-- string read
13, essentially using statement
is essentially a try {......} finally statement block
Using all the classes you want to use keywords to release resources must implement the IDisposable interface
Close to perform the Dispose () and recovered objects
Use Using statement block does not catch an exception, because there Using only a try ...... finally operation, and there is no catch block, so the using statement block also add their own try ...... catch block to catch an exception
14, serialization and deserialization
Serialization characteristics
Binary formatter
Serialization: binary formatter object in the field and value "text" manner saved into a text
[Serializable]
BinaryFormatter class method
Serialize-- graph serialization to the object in the stream
Deserialize-- serialized objects made from the stream, the returned object is deserialized obtained
Serialization Note:
a, die serialized type must be marked as: [Serializable]
b, the type of the parent class must also be marked as: [Serializable], when there is a reflected parameter must be "whether Looking parent class object"
c, all members of the type of that type must also labeled: [Serializable]
d, serialization of only the sequence number field in the class (serialized some state information only)
De-serialization: binary formatter, first create an identical object, and then set the value to see "text" in the field of preservation of the field. According to text (fields, field values, class names) in the name of the class information, creating a new object using reflection techniques, and set the value of a field to a new object