C # How to read files

Key knowledge points:

1. filestream file_read = new filestream ("1.txt", filemode. Open, fileaccess. Read); // only the read permission is allowed to open the 1.txt file.

Parameter 1:

"1.txt": file path, usually represented by string variables or string constants, for example," d: \ 1.txt ";

Parameter 2:

Filemode. Open: open mode. If this mode exists, it is opened; otherwise, an exception is thrown.

Filemode. append: append mode. You can only use the fileaccess. Write Permission to open a file or create a new file and find the end of the file.

Filemode. Create: Specifies the file created by the operating system. If the file with the same name already exists, it is overwritten.

Filemode. createnew: Specifies the file created by the operating system. If the file with the same name already exists, an exception is thrown.

Filemode. openorcreate: if the file exists, open it. Create a new file if it does not exist.

Filemode. truncate: open an existing file. Once opened, the file is truncated to 0 bytes.

Parameter 3:

Fileaccess. Read: Read-only write permission

Fileaccess. readwrite: read/write permission

Fileaccess. Write: Write Permission

Ii. streamreader sr = new streamreader (file_read, encoding. Default); // get read/stream read/1.txt

Parameter 1:

File_read: get the file stream, that is, get the specified file stream, which is usually represented by a string variable.

Parameter 2:

Encoding. Default: obtains the encoding of the current ANSI code page of the operating system.

Encoding. utf8: Get the UTF-8 encoding.

Encoding. Unicode: Get the encoding in unocode format

Encoding. ASCII: Get the encoding in ascll format

Encoding. Convert (encoding, encoding, byte []): converts one encoding method to another.

Encoding. Convert (encoding, encoding, byte [], int32, int32): converts a range from one encoding method to another encoding method.

3. String [] filelist = file. readalllines ("1.txt", encoding. Default); // read all the lines in the file and save them to the string array.

4. String line = Sr. Readline (); // read the content of a file row and obtain the content from the read stream.

Example 1:

Core Method: String [] filelist = file. readalllines ("1.txt", encoding. Default); // read all the lines in the file and save them to the string array.

The Code is as follows:

Using system; using system. collections. generic; using system. text; using system. io; namespace studyread {class program {static void main (string [] ARGs) {filestream file_read = new filestream ("1.txt", filemode. open, fileaccess. read); // create a new file stream. Only the read permission is allowed to open the 1.txt file string [] filelist = file. readalllines ("1.txt", encoding. default); // read all the lines in the file content and save them to the string array. // Print the read content cyclically. For (INT I = 0; I <= filelist. length-1; I ++) {console. writeline ("Row {0} content: {1}", I, filelist [I]);} console. readkey ();}}}

Run:

Example 2:

Core Statement: String line = Sr. Readline (); // read the content of a file row and obtain the content from the read stream.

The Code is as follows:

Using system; using system. collections. generic; using system. text; using system. io; namespace studyread {class program {static void main (string [] ARGs) {filestream file_read = new filestream ("1.txt", filemode. open, fileaccess. read); // create a new file stream. Only the read permission is limited to open the 1.txt file streamreader sr = new streamreader (file_read, encoding. default); // create a new read-in-stream file stream string line = sr. readline (); // read a row of memory and save it to the string line console. writeline (line); console. readkey ();}}}

Run:

Of course, the code in the above column can also read all the content through loops to achieve the effect of Example 1.

Modify the source code as follows:

Using system; using system. collections. generic; using system. text; using system. io; namespace studyread {class program {static void main (string [] ARGs) {filestream file_read = new filestream ("1.txt", filemode. open, fileaccess. read); // create a new file stream. Only the read permission is limited to open the 1.txt file streamreader sr = new streamreader (file_read, encoding. default); // create a new read-in stream to fetch the file stream string [] filelist = file. readalllines ("1.txt", encoding. ASCII); // It is mainly used to obtain Total number of rows filelist. length string line; // defines the string variable line, used to save the read content // read and print each row of the file cyclically, that is, for (INT I = 0; I <= filelist. length-1; I ++) {line = sr. readline (); // read a row and save it to the string line. Console. writeline (line) ;}console. readkey ();}}}

Program:

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