C# finally

In C#, the finally block is used to execute code no matter whether an exception is thrown or not. This ensures that any resources opened in the try block are properly closed or released, even if an exception occurs. In this tutorial, we'll discuss the syntax, example, and usage of the finally block in C#.

Syntax

The syntax for the finally block in C# is as follows:

try {
   // code that may throw an exception
}
catch(Exception ex) {
   // code to handle the exception
}
finally {
   // code that will always be executed
}

The try block contains the code that may throw an exception. The catch block contains code to handle the exception. The finally block contains code that will always be executed regardless of whether an exception is thrown or not. The finally block is optional.

Example

Let's say we want to read a file, process its contents, and close it afterward. Here's how we can implement it using the try-catch-finally block:

StreamReader file = null;
try {
   file = new StreamReader("test.txt");
   string line;
   while ((line = file.ReadLine()) != null) {
      Console.WriteLine(line);
   }
}
catch (Exception ex) {
   Console.WriteLine(ex.Message);
}
finally {
   if (file != null) {
      file.Close();
   }
}

In the example above, we first try to open the text file "test.txt" and read its contents. If an exception is thrown, we catch it and print the exception message to the console. Then, we close the file in the finally block to ensure that the file is properly closed or released no matter whether an exception is thrown or not.

Output

When we run the example code above, the output will be the contents of the "test.txt" file, if any, printed to the console.

Explanation

In the example above, we used the try-catch-finally block to properly read a file, process its contents, and close it afterward. The try block contains the code to open and read the file. The catch block catches any exceptions that may be thrown when reading the file. The finally block always closes the file, regardless of whether an exception was thrown or not.

Use

The finally block is useful for ensuring that any resources opened in the try block are properly closed or released, even if an exception occurs. You can use the finally block to close files, database connections, and other resources that require explicit closing or releasing.

Important Points

• The finally block is optional, but it's good programming practice to include it to ensure proper resource management.
• Any code in the finally block will always be executed, regardless of whether an exception is thrown or not.
• The finally block should be used to release any resources opened in the try block, such as files, database connections, or network resources.
• The finally block can't be used with only a try block. You need a catch or both catch and finally block.

Summary

In this tutorial, we discussed the syntax, example, and usage of the finally block in C#. We covered how to properly read a file, process its contents, and close it using the try-catch-finally block. We also discussed the important points to keep in mind when using the finally block. With this knowledge, you can ensure that any resources opened in the try block are properly closed or released, even if an exception occurs.