How to: Determine Whether a String Represents a Numeric Value (C# Programming Guide)
To determine whether a string is a valid representation of a specified numeric type, use the static TryParse method that is implemented by all primitive numeric types and also by types such as DateTime and IPAddress. The following example shows how to determine whether "108" is a valid int.
int i = 0; string s = "108"; bool result = int.TryParse(s, out i); //i now = 108
If the string contains nonnumeric characters or the numeric value is too large or too small for the particular type you have specified, TryParse returns false and sets the out parameter to zero. Otherwise, it returns true and sets the out parameter to the numeric value of the string.
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A string may contain only numeric characters and still not be valid for the type whose TryParse method that you use. For example, "256" is not a valid value for byte but it is valid for int. "98.6" is not a valid value for int but it is a valid decimal. |
The following examples show how to use TryParse with string representations of long, byte, and decimal values.
string numString = "1287543"; //"1287543.0" will return false for a long long number1 = 0; bool canConvert = long.TryParse(numString, out number1); if (canConvert == true) Console.WriteLine("number1 now = {0}", number1); else Console.WriteLine("numString is not a valid long"); byte number2 = 0; numString = "255"; // A value of 256 will return false canConvert = byte.TryParse(numString, out number2); if (canConvert == true) Console.WriteLine("number2 now = {0}", number2); else Console.WriteLine("numString is not a valid byte"); decimal number3 = 0; numString = "27.3"; //"27" is also a valid decimal canConvert = decimal.TryParse(numString, out number3); if (canConvert == true) Console.WriteLine("number3 now = {0}", number3); else Console.WriteLine("number3 is not a valid decimal");
