C# Regular Expression for email validation in DataAnnotations - Double backslash

Question

Saw this code for regular expression validation of an email address via data annotations.

I Can't work out the purpose of the double backslash.

To me it's saying there must be a backslash in the email - but I know that this isn't what it is doing!!!

 [RegularExpression(".+\\@.+\\..+",   ErrorMessage="Please enter a valid email")]

Answer 1

The backslash is an escape character both in C# and in a regex. So, in C#, "\\" equals to a single backslash. The resulting backslash is then used to escape the ., which is a metacharacter and therefore must be escaped. I don't know why the @ is escaped however.