RegEx for matching “A-Z, a-z, 0-9, _” and “.”

Question

I need a regex which will allow only A-Z, a-z, 0-9, the _ character, and dot (.) in the input.

I tried:

[A-Za-z0-9_.] 

But, it did not

Answer 1

^[A-Za-z0-9_.]+$

From beginning until the end of the string, match one or more of these characters.

Edit:

Note that ^ and $ match the beginning and the end of a line. When multiline is enabled, this can mean that one line matches, but not the complete string.

Use \A for the beginning of the string, and \z for the end.

See for example: http://msdn.microsoft.com/en-us/library/h5181w5w(v=vs.110).aspx