The keyword "params" in C# allows you to declare a parameter array that can accept any number of arguments of the same data type. Here's how it works:
1. To declare a parameter array, you use the keyword "params" followed by the data type and the name of the array parameter. For example, if you want to create a method that accepts multiple integers, you can declare it like this: `public void MyMethod(params int[] numbers) { }`
2. Inside the method, you can treat the `numbers` parameter as an array, even though the caller can pass any number of integers. This means you can use all the array functionality like indexing, looping, and accessing individual elements.
3. When calling the method, you don't need to explicitly create an array. Instead, you can pass a comma-separated list of values, and C# will automatically convert them into an array. For example, you can call the `MyMethod` like this: `MyMethod(1, 2, 3)`.
4. If you want to pass an existing array to the parameter array, you can use the array name followed by an ellipsis (`...`) to indicate that you're passing the array elements individually. For example:
`int[] my Array = { 1, 2, 3 }; My Method(my Array...)`.
5. It's important to note that a parameter array must be the last parameter in a method's parameter list. This means you cannot have any parameters after the parameter array declaration.
Overall, the `params` keyword provides a convenient way to work with a variable number of arguments of the same data type in C#. It allows you to write flexible methods that can accept any number of arguments without the need for explicitly creating an array.