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What I have tried:

not working, i also want to check if it is less then 10 digit then give error
Updated 29-May-21 2:20am
Patrice T 3-Apr-18 12:10pm
"not working it is giving error"
Which error ?
Show code that we can run.

try {
	if (Regex.IsMatch(SubjectString, "\\A[0-9]{10}\\z")) {
		// This is a FULL MATCH
	} else {
		// Nope, no match, do your worst
} catch (ArgumentException ex) {
	// Syntax error in the regular expression
Member 11776570 3-Apr-18 12:07pm
not working it is giving error, i have type mobile number in textbox.
Christiaan van Bergen 3-Apr-18 12:09pm
Show me the number you want to check.
Member 11776570 3-Apr-18 12:15pm
9876543214. this number i want to check but it shuold also check that it should be equal to 10 digits mendatory.
Christiaan van Bergen 3-Apr-18 12:18pm
Right, this number checks out. It IS 10 digits. Make it nine digits and it will fail....of course. Could it be that you have some spaces around your input? Try a .Trim() statement on your input.
Member 11776570 3-Apr-18 12:23pm
not working it is check 9 digit only not 10 digit. i want to check 10 digit mobile no like this 9876543201
Your regex works fine to check your sample data:
Regex reg = new Regex(@"^[0-9]{10}$");
string inputOK = "9876543214";
string inputBad1 = "876543214";
string inputBad2 = "09876543214";
if (reg.IsMatch(inputOK)) Console.WriteLine("OK");
if (!reg.IsMatch(inputBad1)) Console.WriteLine("OK");
if (!reg.IsMatch(inputBad2)) Console.WriteLine("OK");
It gives
So ... the data you are checking is not what you think it is.
Use the debugger to check exactly what is in your input string when you validate it.
If you would like to check if mobile phone number is valid (10 digits), try this:
string[] mobilephones = {"9876543214", "987654321", "98765432142", "A876543214", "87C54d2142"};

string pattern = @"^\d{10}$";

var result = mobilephones
		mobile = x,
		IsValid = Regex.IsMatch(x, pattern),
foreach(var mb in result)
	Console.WriteLine("{0} - {1} valid mobile number",, mb.IsValid ? "is" : "is NOT");

9876543214 - is valid mobile number
987654321 - is NOT valid mobile number
98765432142 - is NOT valid mobile number
A876543214 - is NOT valid mobile number
87C54d2142 - is NOT valid mobile number

For further details, please see: Regex.IsMatch Method[^]

use this it will work properly. it will also check if any alphabets are there or not. in this we can only enter 10 digits number
val UserMobile = findViewById<edittext>(
val msgUserMobile: String = UserMobile.text.toString()

fun String.isMobileValid(): Boolean {
// 11 digit number start with 011 or 010 or 015 or 012
// then [0-9]{8} any numbers from 0 to 9 with length 8 numbers
if(Pattern.matches("(011|012|010|015)[0-9]{8}", msgUserMobile)) {
return true

return false
if(msgUserMobile.trim().length==11&& msgUserMobile.isMobileValid())
{//pass} else {//not valid}
a = int(input("please enter the number: "))
if a.isdigits() and (a.startswith('7') or a.startswith('8') or a.startswith('9')) and len(a) == 10:
Dave Kreskowiak 29-May-21 9:47am
No. An unexplained code snippet is not an acceptable answer. Oh, and your code doesn't even use a regex.

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