What is the purpose of the using keyword in C#?

In C#, the using keyword serves two main purposes:

1. Namespace reference: You can use the “using” keyword to reference other namespaces, allowing you to directly use the types from those references in the current file without the need for the full namespace path.

For example, by referencing the System namespace with the using keyword, you can directly use types from the System namespace without needing to use the full namespace path in the code, such as System.Console.WriteLine(“Hello World”);.

1. Automatic resource management: Using the using keyword, a code block is created that automatically calls the Dispose method of the resource being used when the code block ends, allowing for timely release of resources and preventing resource leaks.

For example, you can use the “using” keyword to create a file stream object and automatically close the file stream and release the file resources at the end of the code block, as shown below:

using (FileStream fileStream = new FileStream("example.txt", FileMode.Open))
{
    // 使用文件流进行一些操作
}

The Dispose method of the file stream object will be automatically called at the end of the code block, ensuring that the file stream is closed and resources are released.