Reading Files using StreamReader
We can open and read files using the C# programming language.
For reading a file, we create a new StreamReader object. The StreamReader object takes in the path of the file.
StreamReader is a data type just like int or float. So the values 1, 2.5f and "Hello World" can be technically referred to as "objects" of the int, float and string data types respectively.
index.cs
Here fileVarName represents the variable name in which we will store the StreamReader object, and fullPath is supposed to be the full path of the file in the form of a string.
For-example we want to open a file "text.txt" on Desktop which has the path C:/Users/Admin/Desktop/text.txt:
index.cs
var textFile = new StreamReader("C:/Users/Admin/Desktop/text.txt");
Consider the text.txt file has the following content:
text.txt
A StreamReader object has a ReadLine method which reads one line from the file and returns it:
index.cs
Output:
The ReadLine method automatically switches the cursor to the next line so when it's called again, it reads the next line if there is any, otherwise it simply returns null (nothing):
index.cs
Output:
For reading all the lines from a file we can use the while loop with a condition which checks if the next line is null or not. Following is a simple way we can do that:
index.cs
Output:
We can make the above code a bit neater using a trick, for that lets take a look at the assignment statements. An assignment statement has a return value as well, which is the value that is being assigned. It can be understood with an example:
index.cs
Output:
It outputs 7 because the statement a = 7 returns 7 which is the value being assigned to a.
We can use this information to do some creative things like assigning the same value to multiple variables in a single statement:
index.cs
Output:
Using this information, we can modify the file reading code to make it shorter removing unnecessary code:
index.cs
Inside the condition we first used an assignment statement line = textFile.ReadLine() which automatically updates the line variable and then checks if it's null from the statement's return value.
After reading the file we must also close it using the Close method, otherwise it can potentially cause memory leaks or the file can be locked and become inaccessible from other places as long as the program is running.
The final code will look something like this:
index.cs
Все було зрозуміло?
Зміст курсу
C# Beyond Basics
C# Beyond Basics
Reading Files using StreamReader
We can open and read files using the C# programming language.
For reading a file, we create a new StreamReader object. The StreamReader object takes in the path of the file.
StreamReader is a data type just like int or float. So the values 1, 2.5f and "Hello World" can be technically referred to as "objects" of the int, float and string data types respectively.
index.cs
Here fileVarName represents the variable name in which we will store the StreamReader object, and fullPath is supposed to be the full path of the file in the form of a string.
For-example we want to open a file "text.txt" on Desktop which has the path C:/Users/Admin/Desktop/text.txt:
index.cs
var textFile = new StreamReader("C:/Users/Admin/Desktop/text.txt");
Consider the text.txt file has the following content:
text.txt
A StreamReader object has a ReadLine method which reads one line from the file and returns it:
index.cs
Output:
The ReadLine method automatically switches the cursor to the next line so when it's called again, it reads the next line if there is any, otherwise it simply returns null (nothing):
index.cs
Output:
For reading all the lines from a file we can use the while loop with a condition which checks if the next line is null or not. Following is a simple way we can do that:
index.cs
Output:
We can make the above code a bit neater using a trick, for that lets take a look at the assignment statements. An assignment statement has a return value as well, which is the value that is being assigned. It can be understood with an example:
index.cs
Output:
It outputs 7 because the statement a = 7 returns 7 which is the value being assigned to a.
We can use this information to do some creative things like assigning the same value to multiple variables in a single statement:
index.cs
Output:
Using this information, we can modify the file reading code to make it shorter removing unnecessary code:
index.cs
Inside the condition we first used an assignment statement line = textFile.ReadLine() which automatically updates the line variable and then checks if it's null from the statement's return value.
After reading the file we must also close it using the Close method, otherwise it can potentially cause memory leaks or the file can be locked and become inaccessible from other places as long as the program is running.
The final code will look something like this:
index.cs
Все було зрозуміло?
