Regular Expression to match Salutation-CodePudding

I used the following regular expression. How can I force user to enter space after Mr., MR., MRs., Mrs,. then at least one character after the space .

[RegularExpression(@"^(Mr. .*|MR. .*|MRS. .*|Mrs. .*|MS. .*|Ms. .*|DR. .*|Dr. .*)", ErrorMessage = "Greeting must begin with Mr., Mrs., Ms., or Dr. and be followed by a name.")]
 public string? Greeting { get; set; }

Fore example: if they enter Mr. Joe Doe or Mr. Joe is valid but they enter Mr. with space only or Mr. without space is invalid.

CodePudding user response：

Try to replace every * with

^(Mr. . |MR. . |MRS. . |Mrs. . |MS. . |Ms. . |DR. . |Dr. . )

I believe this could help.

CodePudding user response：

You can try something like this to get started

^[Mr\.] [ ] [A-Za-z]{0,25}[ ]?[A-za-z]{1,25}

This should match the use cases you gave.

The backslash escapes the period so it matches a literal period.

The curly brackets give a range of how many patterns are allowed of the grouping before it.

The question mark makes the bracket grouping before it optional.

Also, give this site a shot to try out your regex in real time. https://regexr.com/

CodePudding user response：

Use

^(?:[DM][rR][sS]?|M[Ss])\. .

See proof.

EXPLANATION

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  ^                        the beginning of the string
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  (?:                      group, but do not capture:
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    [DM]                     any character of: 'D', 'M'
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    [rR]                     any character of: 'r', 'R'
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    [sS]?                    any character of: 's', 'S' (optional
                             (matching the most amount possible))
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   |                        OR
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    M                        'M'
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    [Ss]                     any character of: 'S', 's'
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  )                        end of grouping
--------------------------------------------------------------------------------
  \.                       '.'
--------------------------------------------------------------------------------
                           ' '
--------------------------------------------------------------------------------
  .                        any character except \n (1 or more times
                           (matching the most amount possible))

CodePudding user response：

Couple of issues

. matches "any character" so saying Mr. allows someone to write Mra Mrb etc - put a \ before it or put it in a character class (surround it with [ ])

* means "zero or more of" so a regex of Mr. .* allows them to write zero characters for the name. To quantify "one or more" we use instead of *

If you want to do away with repetitive elements you could

(M[rRsS]|M(RS|rs)|D[rR])\. \w

The first one takes care of Mr and Ms, second takes care of Mrs, third Dr, then is the common element of "literally a period" followed by a succession of word characters