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Checking For Numeric Characters in a String Using C#
Here are a number of ways you can check a string for numeric characters:
Firstly you can create a simple function like:
public bool OnlyNumeric(string s)
{
int i = 0;
while (i='0' && s[i]<='9')
i++;
return i==s.Length;
}
You could also do the check using a try/catch and if exception is thrown do whetever you do when OnlyNumeric returns.
public bool OnlyNumeric(string s)
{
try
{
Convert.ToInt64(s);
return true;
}
catch
{
return false;
}
}
However with the second option exception handling is a performance expensive operation.
You could further simplify the solution by using char.IsNumber(...) in the while condition:
public bool OnlyNumeric(string s)
{
int i = 0;
while (i < s.Length && char.IsNumber(s[i]))
i++;
return i == s.Length;
}
A further option is to use regular expressions. This regular expression ^[0-9]*$ means that:
- ^ from start of string
- [0-9] between 0-9
- [0-9]* all numbers
- $ end of string
string[] arrNumbers = {"12aa","123","111","aaa"};
Regex r = new Regex("^[0-9]*$");
foreach (string a in arrNumbers)
{
if (r.IsMatch(a))
{
Console.WriteLine("this is a Number");
}
else
{
Console.WriteLine("This is not a Number");
}
}
The following regular expression pattern searches for any non numeric character and if found returns true.
Match m;
m = Regex.Match(inputStr, @"[^\d]+|^$"); if( m.Success )
{
MessageBox.Show("String was not all numeric characters");
}
else
{
MessageBox.Show("String IS ALL numeric characters");
}
Note the use of "|^$" in the pattern is so that it will also catch an empty string.
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