Checking if an object is a number in C

Question

I d like to check if an object is a number so that  ToString   would result in a string containing digits and   -    Is it possible by simple type checking in  net  like  if  p is Number     Or Should I convert to string  then try parsing to double   Update  To clarify my object is int  uint  float  double  and so on it isn t a string  I m trying to make a function that would serialize any object to xml like this    lt string gt content lt  string gt    or   lt numeric gt 123 3 lt  numeric gt    or raise an exception

User · Answer

Assuming your input is a string     There are 2 ways   use Double TryParse    double temp  bool isNumber   Double TryParse input  out temp     use Regex   bool isNumber   Regex IsMatch input   -  d     d

User · Answer

There are three different concepts there    to check if it is a number  i e  a  typically boxed  numeric value itself   check the type with is - for example if obj is int        to check if a string could be parsed as a number  use TryParse   but if the object isn t a number or a string  but you suspect ToString   might give something that looks like a number  then call ToString   and treat it as a string   In both the first two cases  you ll probably have to handle separately each numeric type you want to support  double decimal int  - each have different ranges and accuracy  for example   You could also look at regex for a quick rough check

User · Answer

You will simply need to do a type check for each of the basic numeric types  Here s an extension method that should do the job  public static bool IsNumber this object value        return value is sbyte                value is byte                value is short                value is ushort                value is int                value is uint                value is long                value is ulong                value is float                value is double                value is decimal     This should cover all numeric types  Update It seems you do actually want to parse the number from a string during deserialisation  In this case  it would probably just be best to use double TryParse  string value    quot 123 3 quot   double num  if   double TryParse value  out num       throw new InvalidOperationException  quot Value is not a number  quot     Of course  this wouldn t handle very large integers long decimals  but if that is the case you just need to add additional calls to long TryParse   decimal TryParse   whatever else

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If your requirement is really       ToString   would result in a string   containing digits and   -     and you want to use double TryParse then you need to use the overload that takes a NumberStyles parameter  and make sure you are using the invariant culture     For example for a number which may have a leading sign  no leading or trailing whitespace  no thousands separator and a period decimal separator  use   NumberStyles style       NumberStyles AllowLeadingSign       NumberStyles AllowDecimalPoint    double TryParse input  style  CultureInfo InvariantCulture  out result

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Take advantage of the IsPrimitive property to make a handy extension method   public static bool IsNumber this object obj        if  Equals obj  null                 return false             Type objType   obj GetType        objType   Nullable GetUnderlyingType objType     objType       if  objType IsPrimitive                return objType    typeof bool   amp  amp               objType    typeof char   amp  amp               objType    typeof IntPtr   amp  amp               objType    typeof UIntPtr              return objType    typeof decimal       EDIT  Fixed as per comments  The generics were removed since  GetType   boxes value types  Also included fix for nullable values

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There are some great answers above  Here is an all-in-one solution  Three overloads for different circumstances      Extension method  call for any object  eg  if  x IsNumeric        public static bool IsNumeric this object x    return  x  null   false   IsNumeric x GetType            Method where you know the type of the object public static bool IsNumeric Type type    return IsNumeric type  Type GetTypeCode type          Method where you know the type and the type code of the object public static bool IsNumeric Type type  TypeCode typeCode    return  typeCode    TypeCode Decimal     type IsPrimitive  amp  amp  typeCode    TypeCode Object  amp  amp  typeCode    TypeCode Boolean  amp  amp  typeCode    TypeCode Char

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Yes  this works   object x   1  Assert That x is int     For a floating point number you would have to test using the float type   object x   1f  Assert That x is float

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You could use code like this   if  n is IConvertible    return   IConvertible  n  ToDouble CultureInfo CurrentCulture   else      Cannot be converted    If your object is an Int32  Single  Double etc  it will perform the conversion  Also  a string implements IConvertible but if the string isn t convertible to a double then a FormatException will be thrown

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Rather than rolling your own  the most reliable way to tell if an in-built type is numeric is probably to reference Microsoft VisualBasic and call Information IsNumeric object value   The implementation handles a number of subtle cases such as char   and HEX and OCT strings

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Taken from Scott Hanselman s Blog   public static bool IsNumeric object expression        if  expression    null      return false       double number      return Double TryParse  Convert ToString  expression                                               CultureInfo InvariantCulture                              System Globalization NumberStyles Any                             NumberFormatInfo InvariantInfo                             out number

User · Answer

While writing my own object IsNumeric   extension method based on Saul Dolgin s answer to this question I ran into a potential issue in that you will get an OverflowException if you try it with double MaxValue or double MinValue    My  solution  was to combine the accepted answer from Noldorin with the one from Saul Dolgin and add a pattern matching switch before trying to parse anything  and use some C 7 goodness to tidy up a bit    public static bool IsNumeric this object obj        if  obj    null  return false       switch  obj                case sbyte    return true          case byte    return true          case short    return true          case ushort    return true          case int    return true          case uint    return true          case long    return true          case ulong    return true          case float    return true          case double    return true          case decimal    return true             string s   Convert ToString obj  CultureInfo InvariantCulture        return double TryParse s  NumberStyles Any  NumberFormatInfo InvariantInfo  out double

[c#] Checking if an object is a number in C#

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