Exercise - Use the Remove() and Replace() methods

8 minutes

In this exercise, you remove characters from a string using the Remove() method and replace characters using the Replace() method.

Sometimes, you need to modify the contents of a string, removing or replacing characters. While you could replace characters with the tools you already know, it requires a bit of temporarily storing and stitching strings back together. Fortunately, the string data type has other built-in methods, Remove() and Replace(), for these specialized scenarios.

Use the `Remove()` method

You would typically use Remove() when there's a standard and consistent position of the characters you want to remove from the string.

This exercise has data stored in older files having a fixed length, and with character positions allocated for certain fields of information. The first five digits represent a customer identification number. The next 20 digits contain a customer's name. The next six positions represent the customer's latest invoice amount, and the last three positions represent the number of items ordered on that invoice.

In the following steps, you need to remove the customer's name to format the data so that it can be sent to a separate process. Since you know the exact position and length of the user's name, you can easily remove it using the Remove() method.

Remove characters in specific locations from a string

Delete or use the line comment operator // to comment out all of the code from the previous exercises.

Update your code in the Visual Studio Code Editor as follows:

string data = "12345John Smith          5000  3  ";
string updatedData = data.Remove(5, 20);
Console.WriteLine(updatedData);

On the Visual Studio Code File menu, select Save.

The Program.cs file must be saved before building or running the code.
In the EXPLORER panel, to open a Terminal at your TestProject folder location, right-click TestProject, and then select Open in Integrated Terminal.

A Terminal panel should open, and should include a command prompt showing that the Terminal is open to your TestProject folder location.
At the Terminal command prompt, to run your code, type dotnet run and then press Enter.

You should see the following output:
```
123455000  3  
```
The Remove() method works similarly to the Substring() method. You supply a starting position and the length to remove those characters from the string.

Use the `Replace()` method

The Replace() method is used when you need to replace one or more characters with a different character (or no character). The Replace() method is different from the other methods used so far, it replaces every instance of the given characters, not just the first or last instance.

Remove characters no matter where they appear in a string

Update your code in the Visual Studio Code Editor as follows:

string message = "This--is--ex-amp-le--da-ta";
message = message.Replace("--", " ");
message = message.Replace("-", "");
Console.WriteLine(message);

Save your code file, and then use Visual Studio Code to run your code.

You should see the following output:
```
This is example data
```
Here you used the Replace() method twice. The first time you replaced the string -- with a space. The second time you replaced the string - with an empty string, which completely removes the character from the string.

Recap

Here are two important things to remember:

The Remove() method works like the Substring() method, except that it deletes the specified characters in the string.
The Replace() method swaps all instances of a string with a new string.