how to validate string by regular expression

Question

1.00/5 (1 vote)

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I want to insert value like
string1.string2
string1_string2
string1 string2

my code is

C#

 Regex str = new Regex(@"[a-zA-Z0-9]+$");
string string1="hello";
string string2="codeproject";
 if (str.IsMatch(string1+".."+string2))
            {
                Console.WriteLine("yes");
            }
            else
                Console.WriteLine("no");

output is yes

Posted 14-Mar-14 8:15am

Member 7909353

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Matt T Heffron · Accepted Answer · 2014-03-14T08:21:00

Solution 1

You only anchored the end of the pattern.
All this tests is that there is at least 1 alpha-numeric at the end of the test-string.
You probably wanted:

C#

Regex str = new Regex(@"^[a-zA-Z0-9]+$");

to pattern match the whole string.

I'm unclear about what you mean by:

I want to insert value like 
string1.string2
string1_string2
string1 string2

What does that have to do with the pattern?

[Edit: following comment below]
How about:

C#

Regex str = new Regex(@"^[a-zA-Z0-9]+[ \._][a-zA-Z0-9]+$");

Will take two alphanumeric sequences separated by space, dot or underscore.

[Edit #2]
If you want to also match just a single alphanumeric sequence as well as two separated sequences, make the separator and second sequence optional:

C#

Regex str = new Regex(@"^[a-zA-Z0-9]+(?:[ \._][a-zA-Z0-9]+)?$");

Posted 14-Mar-14 8:21am

Matt T Heffron

Updated 20-Mar-14 6:40am

v6

Comments

Member 7909353 14-Mar-14 14:32pm

I want to save name like above example only

Matt T Heffron 14-Mar-14 14:48pm

Please see edited solution

Member 7909353 14-Mar-14 15:00pm

thank you

Matt T Heffron 14-Mar-14 16:17pm

You're welcome.
Can you please formally "Accept Solution" with the green button?

Member 7909353 20-Mar-14 2:55am

I want
string1
string1.string2
string1_string2
string1 string2

Matt T Heffron 20-Mar-14 12:39pm

Please see the re-edited solution

Sergey Alexandrovich Kryukov 14-Mar-14 15:15pm

Sure, a 5.
—SA

Matt T Heffron 14-Mar-14 16:17pm

Thanks.

Maciej Los 14-Mar-14 17:08pm

Agree with Sergey ;)

Matt T Heffron 14-Mar-14 17:15pm

Thanks.