A regular expression or pattern matching is nothing but a way in which we can check whether an input string is correct or not. This is possible with the use of the Regex class of the System.Text.RegularExpressions namespace.
Pattern matching is very important while we are working to validate text input. Here, regular expression plays an important role.
Patterns are very flexible and provide us with a way to make our own pattern to validate the input.
There are various constructs that help us define the regular expression. Hence, we need to make them important in our programming where we need validated input. These constructs are character classes, character escapes, quantifiers, and so on.