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How to validate whether a string is a number in C#?
A string having number can be validated using int.TryParse or int.Parse.
Int.Parse throws an exception if it cannot parse the string to an integer, whereas Int.TryParse returns a bool indicating whether it succeeded. Also, Int.TryParse has an out parameter which has the value of the parsed string.
Example
using System;
namespace DemoApplication {
class Program {
static void Main(string[] args) {
string numberString = "123";
int number = 0;
if(int.TryParse(numberString, out number)) {
Console.WriteLine($"Try Parse Interger Number: {number}");
}
Console.WriteLine($"Parse Interger Number: {int.Parse(numberString)}");
Console.ReadLine();
}
}
}Output
The output of the code is
Try Parse Interger Number: 123 Parse Interger Number: 123
In the above example since int.Tryparse returns a boolean value along with the parsed string in the out parameter, the if condition returns true. Also, int.Parse return the integer value as the string contains a proper number.
Example
using System;
namespace DemoApplication {
class Program {
static void Main(string[] args) {
string numberString = "A123";
int number = 0;
if(int.TryParse(numberString, out number)) {
Console.WriteLine($"Try Parse Interger Number: {number}");
}
elsem{
Console.WriteLine($"String doesnot have a proper number");
}
Console.ReadLine();
}
}
}Output
The output of the above code is
String doesnot have a proper number
As the string does not have a proper number, the int.Tryparse will return false and the else part of the code is executed. In the same case, int.Parse will throw exception like below.
Example
using System;
namespace DemoApplication {
class Program {
static void Main(string[] args) {
string numberString = "A123";
Console.WriteLine($"Parse Interger Number: {int.Parse(numberString)}");
//Exception: Input string was not in correct format.
}
}
}
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