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TryParsing from an object list to int | c#

I'm trying to take objects out of an object list to an int list. If the object list's value contains a string than I want to convert it to an int. the error that I'm getting is "cannot convert from 'object' to 'System.ReadOnlySpan'. I've tried looking up examples and information about lists made of objects but couldn't find anything.
I'm also at a loss as to what to do with the 'else' part of the code.
public class ListFilterer
{
public static IEnumerable(int) GetIntegersFromList(List(object) listOfItems)
{
List<int> Integers = new List<int>();
foreach (var value in listOfItems)
{
int number = 0;
bool success = Int32.TryParse(value, out number);
if (success)
{
Integers.Add(number);
}
else
{
Integers.Add(number);
}
}
return Integers;
}
}

It'll probably work out if you TryParse value.ToString() instead, if you're looking for anything that might look like an int and can be converted to an int. If you only want things that actually are ints, something like if(value is int number) should work if your c# version is recent. If it's older you may have to if(value is int) and then cast the value inside the if
Your code can be simplified to:
foreach(...){
int.TryParse(value.ToString(), out var n);
integers.Add(n);
}
Or
foreach(...){
if(value is int)
integers.Add((int)value);
else
integers.Add(0);
}

You could simply use:
var ints = listOfItems
.Select(o => { int.TryParse(o.ToString(), out int num); return num;} )
.ToList();
This will work as you wish, as if conversion fails num is 0 by default.

If Try Parse fails number is automatically 0 so you can directly write this
Int32.TryParse(value, out int number)
Integers.Add(number);

Maybe you can find the better way
var intList = objs.ConvertAll(delegate (object obj) { return (int)obj; });

Using unicode characters bigger than 2 bytes with .Net

I'm using this code to generate U+10FFFC
var s = Encoding.UTF8.GetString(new byte[] {0xF4,0x8F,0xBF,0xBC});
I know it's for private-use and such, but it does display a single character as I'd expect when displaying it. The problems come when manipulating this unicode character.
If I later do this:
foreach(var ch in s)
{
Console.WriteLine(ch);
}
Instead of it printing just the single character, it prints two characters (i.e. the string is apparently composed of two characters). If I alter my loop to add these characters back to an empty string like so:
string tmp="";
foreach(var ch in s)
{
Console.WriteLine(ch);
tmp += ch;
}
At the end of this, tmp will print just a single character.
What exactly is going on here? I thought that char contains a single unicode character and I never had to worry about how many bytes a character is unless I'm doing conversion to bytes. My real use case is I need to be able to detect when very large unicode characters are used in a string. Currently I have something like this:
foreach(var ch in s)
{
if(ch>=0x100000 && ch<=0x10FFFF)
{
Console.WriteLine("special character!");
}
}
However, because of this splitting of very large characters, this doesn't work. How can I modify this to make it work?

U+10FFFC is one Unicode code point, but string's interface does not expose a sequence of Unicode code points directly. Its interface exposes a sequence of UTF-16 code units. That is a very low-level view of text. It is quite unfortunate that such a low-level view of text was grafted onto the most obvious and intuitive interface available... I'll try not to rant much about how I don't like this design, and just say that not matter how unfortunate, it is just a (sad) fact you have to live with.
First off, I will suggest using char.ConvertFromUtf32 to get your initial string. Much simpler, much more readable:
var s = char.ConvertFromUtf32(0x10FFFC);
So, this string's Length is not 1, because, as I said, the interface deals in UTF-16 code units, not Unicode code points. U+10FFFC uses two UTF-16 code units, so s.Length is 2. All code points above U+FFFF require two UTF-16 code units for their representation.
You should note that ConvertFromUtf32 doesn't return a char: char is a UTF-16 code unit, not a Unicode code point. To be able to return all Unicode code points, that method cannot return a single char. Sometimes it needs to return two, and that's why it makes it a string. Sometimes you will find some APIs dealing in ints instead of char because int can be used to handle all code points too (that's what ConvertFromUtf32 takes as argument, and what ConvertToUtf32 produces as result).
string implements IEnumerable<char>, which means that when you iterate over a string you get one UTF-16 code unit per iteration. That's why iterating your string and printing it out yields some broken output with two "things" in it. Those are the two UTF-16 code units that make up the representation of U+10FFFC. They are called "surrogates". The first one is a high/lead surrogate and the second one is a low/trail surrogate. When you print them individually they do not produce meaningful output because lone surrogates are not even valid in UTF-16, and they are not considered Unicode characters either.
When you append those two surrogates to the string in the loop, you effectively reconstruct the surrogate pair, and printing that pair later as one gets you the right output.
And in the ranting front, note how nothing complains that you used a malformed UTF-16 sequence in that loop. It creates a string with a lone surrogate, and yet everything carries on as if nothing happened: the string type is not even the type of well-formed UTF-16 code unit sequences, but the type of any UTF-16 code unit sequence.
The char structure provides static methods to deal with surrogates: IsHighSurrogate, IsLowSurrogate, IsSurrogatePair, ConvertToUtf32, and ConvertFromUtf32. If you want you can write an iterator that iterates over Unicode characters instead of UTF-16 code units:
static IEnumerable<int> AsCodePoints(this string s)
{
for(int i = 0; i < s.Length; ++i)
{
yield return char.ConvertToUtf32(s, i);
if(char.IsHighSurrogate(s, i))
i++;
}
}
Then you can iterate like:
foreach(int codePoint in s.AsCodePoints())
{
// do stuff. codePoint will be an int will value 0x10FFFC in your example
}
If you prefer to get each code point as a string instead change the return type to IEnumerable<string> and the yield line to:
yield return char.ConvertFromUtf32(char.ConvertToUtf32(s, i));
With that version, the following works as-is:
foreach(string codePoint in s.AsCodePoints())
{
Console.WriteLine(codePoint);
}

As posted already by Martinho, it is much easier to create the string with this private codepoint that way:
var s = char.ConvertFromUtf32(0x10FFFC);
But to loop through the two char elements of that string is senseless:
foreach(var ch in s)
{
Console.WriteLine(ch);
}
What for? You will just get the high and low surrogate that encode the codepoint. Remember a char is a 16 bit type so it can hold just a max value of 0xFFFF. Your codepoint doesn't fit into a 16 bit type, indeed for the highest codepoint you'll need 21 bits (0x10FFFF) so the next wider type would just be a 32 bit type. The two char elements are not characters, but a surrogate pair. The value of 0x10FFFC is encoded into the two surrogates.

While #R. Martinho Fernandes's answer is correct, his AsCodePoints extension method has two issues:
It will throw an ArgumentException on invalid code points (high surrogate without low surrogate or vice versa).
You can't use char static methods that take (char) or (string, int) (such as char.IsNumber()) if you only have int code points.
I've split the code into two methods, one similar to the original but returns the Unicode Replacement Character on invalid code points. The second method returns a struct IEnumerable with more useful fields:
StringCodePointExtensions.cs
public static class StringCodePointExtensions {
const char ReplacementCharacter = '\ufffd';
public static IEnumerable<CodePointIndex> CodePointIndexes(this string s) {
for (int i = 0; i < s.Length; i++) {
if (char.IsHighSurrogate(s, i)) {
if (i + 1 < s.Length && char.IsLowSurrogate(s, i + 1)) {
yield return CodePointIndex.Create(i, true, true);
i++;
continue;
} else {
// High surrogate without low surrogate
yield return CodePointIndex.Create(i, false, false);
continue;
}
} else if (char.IsLowSurrogate(s, i)) {
// Low surrogate without high surrogate
yield return CodePointIndex.Create(i, false, false);
continue;
}
yield return CodePointIndex.Create(i, true, false);
}
}
public static IEnumerable<int> CodePointInts(this string s) {
return s
.CodePointIndexes()
.Select(
cpi => {
if (cpi.Valid) {
return char.ConvertToUtf32(s, cpi.Index);
} else {
return (int)ReplacementCharacter;
}
});
}
}
CodePointIndex.cs:
public struct CodePointIndex {
public int Index;
public bool Valid;
public bool IsSurrogatePair;
public static CodePointIndex Create(int index, bool valid, bool isSurrogatePair) {
return new CodePointIndex {
Index = index,
Valid = valid,
IsSurrogatePair = isSurrogatePair,
};
}
}
To the extent possible under law, the person who associated CC0 with this work has waived all copyright and related or neighboring rights to this work.

Yet another alternative to enumerate the UTF32 characters in a C# string is to use the System.Globalization.StringInfo.GetTextElementEnumerator method, as in the code below.
public static class StringExtensions
{
public static System.Collections.Generic.IEnumerable<UTF32Char> GetUTF32Chars(this string s)
{
var tee = System.Globalization.StringInfo.GetTextElementEnumerator(s);
while (tee.MoveNext())
{
yield return new UTF32Char(s, tee.ElementIndex);
}
}
}
public struct UTF32Char
{
private string s;
private int index;
public UTF32Char(string s, int index)
{
this.s = s;
this.index = index;
}
public override string ToString()
{
return char.ConvertFromUtf32(this.UTF32Code);
}
public int UTF32Code { get { return char.ConvertToUtf32(s, index); } }
public double NumericValue { get { return char.GetNumericValue(s, index); } }
public UnicodeCategory UnicodeCategory { get { return char.GetUnicodeCategory(s, index); } }
public bool IsControl { get { return char.IsControl(s, index); } }
public bool IsDigit { get { return char.IsDigit(s, index); } }
public bool IsLetter { get { return char.IsLetter(s, index); } }
public bool IsLetterOrDigit { get { return char.IsLetterOrDigit(s, index); } }
public bool IsLower { get { return char.IsLower(s, index); } }
public bool IsNumber { get { return char.IsNumber(s, index); } }
public bool IsPunctuation { get { return char.IsPunctuation(s, index); } }
public bool IsSeparator { get { return char.IsSeparator(s, index); } }
public bool IsSurrogatePair { get { return char.IsSurrogatePair(s, index); } }
public bool IsSymbol { get { return char.IsSymbol(s, index); } }
public bool IsUpper { get { return char.IsUpper(s, index); } }
public bool IsWhiteSpace { get { return char.IsWhiteSpace(s, index); } }
}

Search for a string in Enum and return the Enum

I have an enumeration:
public enum MyColours
{
Red,
Green,
Blue,
Yellow,
Fuchsia,
Aqua,
Orange
}
and I have a string:
string colour = "Red";
I want to be able to return:
MyColours.Red
from:
public MyColours GetColour(string colour)
So far i have:
public MyColours GetColours(string colour)
{
string[] colours = Enum.GetNames(typeof(MyColours));
int[] values = Enum.GetValues(typeof(MyColours));
int i;
for(int i = 0; i < colours.Length; i++)
{
if(colour.Equals(colours[i], StringComparison.Ordinal)
break;
}
int value = values[i];
// I know all the information about the matched enumeration
// but how do i convert this information into returning a
// MyColour enumeration?
}
As you can see, I'm a bit stuck. Is there anyway to select an enumerator by value. Something like:
MyColour(2)
would result in
MyColour.Green

check out System.Enum.Parse:
enum Colors {Red, Green, Blue}
// your code:
Colors color = (Colors)System.Enum.Parse(typeof(Colors), "Green");

You can cast the int to an enum
(MyColour)2
There is also the option of Enum.Parse
(MyColour)Enum.Parse(typeof(MyColour), "Red")

Given the latest and greatest changes to .NET (+ Core) and C# 7, here is the best solution:
var ignoreCase = true;
Enum.TryParse("red", ignoreCase , out MyColours colour);
colour variable can be used within the scope of Enum.TryParse

All you need is Enum.Parse.

var color = Enum.Parse<Colors>("Green");

I marked OregonGhost's answer +1, then I tried to use the iteration and realised it wasn't quite right because Enum.GetNames returns strings. You want Enum.GetValues:
public MyColours GetColours(string colour)
{
foreach (MyColours mc in Enum.GetValues(typeof(MyColours)))
if (mc.ToString() == surveySystem)
return mc;
return MyColors.Default;
}

You can use Enum.Parse to get an enum value from the name. You can iterate over all values with Enum.GetNames, and you can just cast an int to an enum to get the enum value from the int value.
Like this, for example:
public MyColours GetColours(string colour)
{
foreach (MyColours mc in Enum.GetNames(typeof(MyColours))) {
if (mc.ToString().Contains(colour)) {
return mc;
}
}
return MyColours.Red; // Default value
}
or:
public MyColours GetColours(string colour)
{
return (MyColours)Enum.Parse(typeof(MyColours), colour, true); // true = ignoreCase
}
The latter will throw an ArgumentException if the value is not found, you may want to catch it inside the function and return the default value.

Try this method.
public static class Helper
{
public static T FromStr<T>(string str) where T : struct, System.Enum
=> System.Enum.TryParse<T>(value:str,ignoreCase:true,result:out var result)
? result
: default;
public static T? FromStrNull<T>(string str) where T : struct, System.Enum
=> System.Enum.TryParse<T>(value: str,ignoreCase: true,result: out var result)
? result
: null;
}
And use it like this
var color = Helper.FromStr<MyColours>("red");

As mentioned in previous answers, you can cast directly to the underlying datatype (int -> enum type) or parse (string -> enum type).
but beware - there is no .TryParse for enums, so you WILL need a try/catch block around the parse to catch failures.

class EnumStringToInt // to search for a string in enum
{
enum Numbers{one,two,hree};
static void Main()
{
Numbers num = Numbers.one; // converting enum to string
string str = num.ToString();
//Console.WriteLine(str);
string str1 = "four";
string[] getnames = (string[])Enum.GetNames(typeof(Numbers));
int[] getnum = (int[])Enum.GetValues(typeof(Numbers));
try
{
for (int i = 0; i <= getnum.Length; i++)
{
if (str1.Equals(getnames[i]))
{
Numbers num1 = (Numbers)Enum.Parse(typeof(Numbers), str1);
Console.WriteLine("string found:{0}", num1);
}
}
}
catch (Exception ex)
{
Console.WriteLine("Value not found!", ex);
}
}
}

One thing that might be useful to you (besides the already valid/good answers provided so far) is the StringEnum idea provided here
With this you can define your enumerations as classes (the examples are in vb.net):
< StringEnumRegisteredOnly(), DebuggerStepThrough(),
ImmutableObject(True)> Public NotInheritable Class
eAuthenticationMethod Inherits StringEnumBase(Of
eAuthenticationMethod)
Private Sub New(ByVal StrValue As String)
MyBase.New(StrValue)
End Sub
< Description("Use User Password Authentication")> Public Shared ReadOnly UsernamePassword As New eAuthenticationMethod("UP")
< Description("Use Windows Authentication")> Public Shared ReadOnly WindowsAuthentication As New eAuthenticationMethod("W")
End Class
And now you could use the this class as you would use an enum: eAuthenticationMethod.WindowsAuthentication and this would be essentially like assigning the 'W' the logical value of WindowsAuthentication (inside the enum) and if you were to view this value from a properties window (or something else that uses the System.ComponentModel.Description property) you would get "Use Windows Authentication".
I've been using this for a long time now and it makes the code more clear in intent.

(MyColours)Enum.Parse(typeof(MyColours), "red", true); // MyColours.Red
(int)((MyColours)Enum.Parse(typeof(MyColours), "red", true)); // 0

You might also want to check out some of the suggestions in this blog post:
My new little friend, Enum<T>
The post describes a way to create a very simple generic helper class which enables you to avoid the ugly casting syntax inherent with Enum.Parse - instead you end up writing something like this in your code:
MyColours colour = Enum<MyColours>.Parse(stringValue);
Or check out some of the comments in the same post which talk about using an extension method to achieve similar.

How to TryParse for Enum value?

I want to write a function which can validate a given value (passed as a string) against possible values of an enum. In the case of a match, it should return the enum instance; otherwise, it should return a default value.
The function may not internally use try/catch, which excludes using Enum.Parse, which throws an exception when given an invalid argument.
I'd like to use something along the lines of a TryParse function to implement this:
public static TEnum ToEnum<TEnum>(this string strEnumValue, TEnum defaultValue)
{
object enumValue;
if (!TryParse (typeof (TEnum), strEnumValue, out enumValue))
{
return defaultValue;
}
return (TEnum) enumValue;
}

Enum.IsDefined will get things done. It may not be as efficient as a TryParse would probably be, but it will work without exception handling.
public static TEnum ToEnum<TEnum>(this string strEnumValue, TEnum defaultValue)
{
if (!Enum.IsDefined(typeof(TEnum), strEnumValue))
return defaultValue;
return (TEnum)Enum.Parse(typeof(TEnum), strEnumValue);
}
Worth noting: a TryParse method was added in .NET 4.0.

As others have said, you have to implement your own TryParse. Simon Mourier is providing a full implementation which takes care of everything.
If you are using bitfield enums (i.e. flags), you also have to handle a string like "MyEnum.Val1|MyEnum.Val2" which is a combination of two enum values. If you just call Enum.IsDefined with this string, it will return false, even though Enum.Parse handles it correctly.
Update
As mentioned by Lisa and Christian in the comments, Enum.TryParse is now available for C# in .NET4 and up.
MSDN Docs

Here is a custom implementation of EnumTryParse. Unlike other common implementations, it also supports enum marked with the Flags attribute.
/// <summary>
/// Converts the string representation of an enum to its Enum equivalent value. A return value indicates whether the operation succeeded.
/// This method does not rely on Enum.Parse and therefore will never raise any first or second chance exception.
/// </summary>
/// <param name="type">The enum target type. May not be null.</param>
/// <param name="input">The input text. May be null.</param>
/// <param name="value">When this method returns, contains Enum equivalent value to the enum contained in input, if the conversion succeeded.</param>
/// <returns>
/// true if s was converted successfully; otherwise, false.
/// </returns>
public static bool EnumTryParse(Type type, string input, out object value)
{
if (type == null)
throw new ArgumentNullException("type");
if (!type.IsEnum)
throw new ArgumentException(null, "type");
if (input == null)
{
value = Activator.CreateInstance(type);
return false;
}
input = input.Trim();
if (input.Length == 0)
{
value = Activator.CreateInstance(type);
return false;
}
string[] names = Enum.GetNames(type);
if (names.Length == 0)
{
value = Activator.CreateInstance(type);
return false;
}
Type underlyingType = Enum.GetUnderlyingType(type);
Array values = Enum.GetValues(type);
// some enums like System.CodeDom.MemberAttributes *are* flags but are not declared with Flags...
if ((!type.IsDefined(typeof(FlagsAttribute), true)) && (input.IndexOfAny(_enumSeperators) < 0))
return EnumToObject(type, underlyingType, names, values, input, out value);
// multi value enum
string[] tokens = input.Split(_enumSeperators, StringSplitOptions.RemoveEmptyEntries);
if (tokens.Length == 0)
{
value = Activator.CreateInstance(type);
return false;
}
ulong ul = 0;
foreach (string tok in tokens)
{
string token = tok.Trim(); // NOTE: we don't consider empty tokens as errors
if (token.Length == 0)
continue;
object tokenValue;
if (!EnumToObject(type, underlyingType, names, values, token, out tokenValue))
{
value = Activator.CreateInstance(type);
return false;
}
ulong tokenUl;
switch (Convert.GetTypeCode(tokenValue))
{
case TypeCode.Int16:
case TypeCode.Int32:
case TypeCode.Int64:
case TypeCode.SByte:
tokenUl = (ulong)Convert.ToInt64(tokenValue, CultureInfo.InvariantCulture);
break;
//case TypeCode.Byte:
//case TypeCode.UInt16:
//case TypeCode.UInt32:
//case TypeCode.UInt64:
default:
tokenUl = Convert.ToUInt64(tokenValue, CultureInfo.InvariantCulture);
break;
}
ul |= tokenUl;
}
value = Enum.ToObject(type, ul);
return true;
}
private static char[] _enumSeperators = new char[] { ',', ';', '+', '|', ' ' };
private static object EnumToObject(Type underlyingType, string input)
{
if (underlyingType == typeof(int))
{
int s;
if (int.TryParse(input, out s))
return s;
}
if (underlyingType == typeof(uint))
{
uint s;
if (uint.TryParse(input, out s))
return s;
}
if (underlyingType == typeof(ulong))
{
ulong s;
if (ulong.TryParse(input, out s))
return s;
}
if (underlyingType == typeof(long))
{
long s;
if (long.TryParse(input, out s))
return s;
}
if (underlyingType == typeof(short))
{
short s;
if (short.TryParse(input, out s))
return s;
}
if (underlyingType == typeof(ushort))
{
ushort s;
if (ushort.TryParse(input, out s))
return s;
}
if (underlyingType == typeof(byte))
{
byte s;
if (byte.TryParse(input, out s))
return s;
}
if (underlyingType == typeof(sbyte))
{
sbyte s;
if (sbyte.TryParse(input, out s))
return s;
}
return null;
}
private static bool EnumToObject(Type type, Type underlyingType, string[] names, Array values, string input, out object value)
{
for (int i = 0; i < names.Length; i++)
{
if (string.Compare(names[i], input, StringComparison.OrdinalIgnoreCase) == 0)
{
value = values.GetValue(i);
return true;
}
}
if ((char.IsDigit(input[0]) || (input[0] == '-')) || (input[0] == '+'))
{
object obj = EnumToObject(underlyingType, input);
if (obj == null)
{
value = Activator.CreateInstance(type);
return false;
}
value = obj;
return true;
}
value = Activator.CreateInstance(type);
return false;
}

In the end you have to implement this around Enum.GetNames:
public bool TryParseEnum<T>(string str, bool caseSensitive, out T value) where T : struct {
// Can't make this a type constraint...
if (!typeof(T).IsEnum) {
throw new ArgumentException("Type parameter must be an enum");
}
var names = Enum.GetNames(typeof(T));
value = (Enum.GetValues(typeof(T)) as T[])[0]; // For want of a better default
foreach (var name in names) {
if (String.Equals(name, str, caseSensitive ? StringComparison.Ordinal : StringComparison.OrdinalIgnoreCase)) {
value = (T)Enum.Parse(typeof(T), name);
return true;
}
}
return false;
}
Additional notes:
Enum.TryParse is included in .NET 4. See here http://msdn.microsoft.com/library/dd991876(VS.100).aspx
Another approach would be to directly wrap Enum.Parse catching the exception thrown when it fails. This could be faster when a match is found, but will likely to slower if not. Depending on the data you are processing this may or may not be a net improvement.
EDIT: Just seen a better implementation on this, which caches the necessary information: http://damieng.com/blog/2010/10/17/enums-better-syntax-improved-performance-and-tryparse-in-net-3-5

Based on .NET 4.5
Sample code below
using System;
enum Importance
{
None,
Low,
Medium,
Critical
}
class Program
{
static void Main()
{
// The input value.
string value = "Medium";
// An unitialized variable.
Importance importance;
// Call Enum.TryParse method.
if (Enum.TryParse(value, out importance))
{
// We now have an enum type.
Console.WriteLine(importance == Importance.Medium);
}
}
}
Reference : http://www.dotnetperls.com/enum-parse

enum EnumStatus
{
NAO_INFORMADO = 0,
ENCONTRADO = 1,
BLOQUEADA_PELO_ENTREGADOR = 2,
DISPOSITIVO_DESABILITADO = 3,
ERRO_INTERNO = 4,
AGARDANDO = 5
}
...
if (Enum.TryParse<EnumStatus>(item.status, out status)) {
}

I have an optimised implementation you could use in UnconstrainedMelody. Effectively it's just caching the list of names, but it's doing so in a nice, strongly typed, generically constrained way :)

There's currently no out of the box Enum.TryParse. This has been requested on Connect (Still no Enum.TryParse) and got a response indicating possible inclusion in the next framework after .NET 3.5. You'll have to implement the suggested workarounds for now.

The only way to avoid exception handling is to use the GetNames() method, and we all know that exceptions shouldn't be abused for common application logic :)

Is caching a dynamically generated function/dictionary permissable?
Because you don't (appear to) know the type of the enum ahead of time, the first execution could generate something subsequent executions could take advantage of.
You could even cache the result of Enum.GetNames()
Are you trying to optimize for CPU or Memory? Do you really need to?

As others already said, if you don't use Try&Catch, you need to use IsDefined or GetNames...
Here are some samples...they basically are all the same, the first one handling nullable enums. I prefer the 2nd one as it's an extension on strings, not enums...but you can mix them as you want!
www.objectreference.net/post/Enum-TryParse-Extension-Method.aspx
flatlinerdoa.spaces.live.com/blog/cns!17124D03A9A052B0!605.entry
mironabramson.com/blog/post/2008/03/Another-version-for-the-missing-method-EnumTryParse.aspx
lazyloading.blogspot.com/2008/04/enumtryparse-with-net-35-extension.html

There is not a TryParse because the Enum's type is not known until runtime. A TryParse that follows the same methodology as say the Date.TryParse method would throw an implicit conversion error on the ByRef parameter.
I suggest doing something like this:
//1 line call to get value
MyEnums enumValue = (Sections)EnumValue(typeof(Sections), myEnumTextValue, MyEnums.SomeEnumDefault);
//Put this somewhere where you can reuse
public static object EnumValue(System.Type enumType, string value, object NotDefinedReplacement)
{
if (Enum.IsDefined(enumType, value)) {
return Enum.Parse(enumType, value);
} else {
return Enum.Parse(enumType, NotDefinedReplacement);
}
}

Have a look at the Enum class (struct ? ) itself. There is a Parse method on that but I'm not sure about a tryparse.

This method will convert a type of enum:
public static TEnum ToEnum<TEnum>(object EnumValue, TEnum defaultValue)
{
if (!Enum.IsDefined(typeof(TEnum), EnumValue))
{
Type enumType = Enum.GetUnderlyingType(typeof(TEnum));
if ( EnumValue.GetType() == enumType )
{
string name = Enum.GetName(typeof(HLink.ViewModels.ClaimHeaderViewModel.ClaimStatus), EnumValue);
if( name != null)
return (TEnum)Enum.Parse(typeof(TEnum), name);
return defaultValue;
}
}
return (TEnum)Enum.Parse(typeof(TEnum), EnumValue.ToString());
}
It checks the underlying type and get the name against it to parse. If everything fails it will return default value.

Identify if a string is a number

If I have these strings:
"abc" = false
"123" = true
"ab2" = false
Is there a command, like IsNumeric() or something else, that can identify if a string is a valid number?

int n;
bool isNumeric = int.TryParse("123", out n);
Update As of C# 7:
var isNumeric = int.TryParse("123", out int n);
or if you don't need the number you can discard the out parameter
var isNumeric = int.TryParse("123", out _);
The var s can be replaced by their respective types!

This will return true if input is all numbers. Don't know if it's any better than TryParse, but it will work.
Regex.IsMatch(input, #"^\d+$")
If you just want to know if it has one or more numbers mixed in with characters, leave off the ^ + and $.
Regex.IsMatch(input, #"\d")
Edit:
Actually I think it is better than TryParse because a very long string could potentially overflow TryParse.

You can also use:
using System.Linq;
stringTest.All(char.IsDigit);
It will return true for all Numeric Digits (not float) and false if input string is any sort of alphanumeric.
Test case
Return value
Test result
"1234"
true
✅Pass
"1"
true
✅Pass
"0"
true
✅Pass
""
true
⚠️Fail (known edge case)
"12.34"
false
✅Pass
"+1234"
false
✅Pass
"-13"
false
✅Pass
"3E14"
false
✅Pass
"0x10"
false
✅Pass
Please note: stringTest should not be an empty string as this would pass the test of being numeric.

I've used this function several times:
public static bool IsNumeric(object Expression)
{
double retNum;
bool isNum = Double.TryParse(Convert.ToString(Expression), System.Globalization.NumberStyles.Any, System.Globalization.NumberFormatInfo.InvariantInfo, out retNum);
return isNum;
}
But you can also use;
bool b1 = Microsoft.VisualBasic.Information.IsNumeric("1"); //true
bool b2 = Microsoft.VisualBasic.Information.IsNumeric("1aa"); // false
From Benchmarking IsNumeric Options
(source: aspalliance.com)
(source: aspalliance.com)

This is probably the best option in C#.
If you want to know if the string contains a whole number (integer):
string someString;
// ...
int myInt;
bool isNumerical = int.TryParse(someString, out myInt);
The TryParse method will try to convert the string to a number (integer) and if it succeeds it will return true and place the corresponding number in myInt. If it can't, it returns false.
Solutions using the int.Parse(someString) alternative shown in other responses works, but it is much slower because throwing exceptions is very expensive. TryParse(...) was added to the C# language in version 2, and until then you didn't have a choice. Now you do: you should therefore avoid the Parse() alternative.
If you want to accept decimal numbers, the decimal class also has a .TryParse(...) method. Replace int with decimal in the above discussion, and the same principles apply.

You can always use the built in TryParse methods for many datatypes to see if the string in question will pass.
Example.
decimal myDec;
var Result = decimal.TryParse("123", out myDec);
Result would then = True
decimal myDec;
var Result = decimal.TryParse("abc", out myDec);
Result would then = False

In case you don't want to use int.Parse or double.Parse, you can roll your own with something like this:
public static class Extensions
{
public static bool IsNumeric(this string s)
{
foreach (char c in s)
{
if (!char.IsDigit(c) && c != '.')
{
return false;
}
}
return true;
}
}

If you want to catch a broader spectrum of numbers, à la PHP's is_numeric, you can use the following:
// From PHP documentation for is_numeric
// (http://php.net/manual/en/function.is-numeric.php)
// Finds whether the given variable is numeric.
// Numeric strings consist of optional sign, any number of digits, optional decimal part and optional
// exponential part. Thus +0123.45e6 is a valid numeric value.
// Hexadecimal (e.g. 0xf4c3b00c), Binary (e.g. 0b10100111001), Octal (e.g. 0777) notation is allowed too but
// only without sign, decimal and exponential part.
static readonly Regex _isNumericRegex =
new Regex( "^(" +
/*Hex*/ #"0x[0-9a-f]+" + "|" +
/*Bin*/ #"0b[01]+" + "|" +
/*Oct*/ #"0[0-7]*" + "|" +
/*Dec*/ #"((?!0)|[-+]|(?=0+\.))(\d*\.)?\d+(e\d+)?" +
")$" );
static bool IsNumeric( string value )
{
return _isNumericRegex.IsMatch( value );
}
Unit Test:
static void IsNumericTest()
{
string[] l_unitTests = new string[] {
"123", /* TRUE */
"abc", /* FALSE */
"12.3", /* TRUE */
"+12.3", /* TRUE */
"-12.3", /* TRUE */
"1.23e2", /* TRUE */
"-1e23", /* TRUE */
"1.2ef", /* FALSE */
"0x0", /* TRUE */
"0xfff", /* TRUE */
"0xf1f", /* TRUE */
"0xf1g", /* FALSE */
"0123", /* TRUE */
"0999", /* FALSE (not octal) */
"+0999", /* TRUE (forced decimal) */
"0b0101", /* TRUE */
"0b0102" /* FALSE */
};
foreach ( string l_unitTest in l_unitTests )
Console.WriteLine( l_unitTest + " => " + IsNumeric( l_unitTest ).ToString() );
Console.ReadKey( true );
}
Keep in mind that just because a value is numeric doesn't mean it can be converted to a numeric type. For example, "999999999999999999999999999999.9999999999" is a perfeclty valid numeric value, but it won't fit into a .NET numeric type (not one defined in the standard library, that is).

I know this is an old thread, but none of the answers really did it for me - either inefficient, or not encapsulated for easy reuse. I also wanted to ensure it returned false if the string was empty or null. TryParse returns true in this case (an empty string does not cause an error when parsing as a number). So, here's my string extension method:
public static class Extensions
{
/// <summary>
/// Returns true if string is numeric and not empty or null or whitespace.
/// Determines if string is numeric by parsing as Double
/// </summary>
/// <param name="str"></param>
/// <param name="style">Optional style - defaults to NumberStyles.Number (leading and trailing whitespace, leading and trailing sign, decimal point and thousands separator) </param>
/// <param name="culture">Optional CultureInfo - defaults to InvariantCulture</param>
/// <returns></returns>
public static bool IsNumeric(this string str, NumberStyles style = NumberStyles.Number,
CultureInfo culture = null)
{
double num;
if (culture == null) culture = CultureInfo.InvariantCulture;
return Double.TryParse(str, style, culture, out num) && !String.IsNullOrWhiteSpace(str);
}
}
Simple to use:
var mystring = "1234.56789";
var test = mystring.IsNumeric();
Or, if you want to test other types of number, you can specify the 'style'.
So, to convert a number with an Exponent, you could use:
var mystring = "5.2453232E6";
var test = mystring.IsNumeric(style: NumberStyles.AllowExponent);
Or to test a potential Hex string, you could use:
var mystring = "0xF67AB2";
var test = mystring.IsNumeric(style: NumberStyles.HexNumber)
The optional 'culture' parameter can be used in much the same way.
It is limited by not being able to convert strings that are too big to be contained in a double, but that is a limited requirement and I think if you are working with numbers larger than this, then you'll probably need additional specialised number handling functions anyway.

UPDATE of Kunal Noel Answer
stringTest.All(char.IsDigit);
// This returns true if all characters of the string are digits.
But, for this case we have that empty strings will pass that test, so, you can:
if (!string.IsNullOrEmpty(stringTest) && stringTest.All(char.IsDigit)){
// Do your logic here
}

You can use TryParse to determine if the string can be parsed into an integer.
int i;
bool bNum = int.TryParse(str, out i);
The boolean will tell you if it worked or not.

If you want to know if a string is a number, you could always try parsing it:
var numberString = "123";
int number;
int.TryParse(numberString , out number);
Note that TryParse returns a bool, which you can use to check if your parsing succeeded.

I guess this answer will just be lost in between all the other ones, but anyway, here goes.
I ended up on this question via Google because I wanted to check if a string was numeric so that I could just use double.Parse("123") instead of the TryParse() method.
Why? Because it's annoying to have to declare an out variable and check the result of TryParse() before you know if the parse failed or not. I want to use the ternary operator to check if the string is numerical and then just parse it in the first ternary expression or provide a default value in the second ternary expression.
Like this:
var doubleValue = IsNumeric(numberAsString) ? double.Parse(numberAsString) : 0;
It's just a lot cleaner than:
var doubleValue = 0;
if (double.TryParse(numberAsString, out doubleValue)) {
//whatever you want to do with doubleValue
}
I made a couple extension methods for these cases:
Extension method one
public static bool IsParseableAs<TInput>(this string value) {
var type = typeof(TInput);
var tryParseMethod = type.GetMethod("TryParse", BindingFlags.Static | BindingFlags.Public, Type.DefaultBinder,
new[] { typeof(string), type.MakeByRefType() }, null);
if (tryParseMethod == null) return false;
var arguments = new[] { value, Activator.CreateInstance(type) };
return (bool) tryParseMethod.Invoke(null, arguments);
}
Example:
"123".IsParseableAs<double>() ? double.Parse(sNumber) : 0;
Because IsParseableAs() tries to parse the string as the appropriate type instead of just checking if the string is "numeric" it should be pretty safe. And you can even use it for non numeric types that have a TryParse() method, like DateTime.
The method uses reflection and you end up calling the TryParse() method twice which, of course, isn't as efficient, but not everything has to be fully optimized, sometimes convenience is just more important.
This method can also be used to easily parse a list of numeric strings into a list of double or some other type with a default value without having to catch any exceptions:
var sNumbers = new[] {"10", "20", "30"};
var dValues = sNumbers.Select(s => s.IsParseableAs<double>() ? double.Parse(s) : 0);
Extension method two
public static TOutput ParseAs<TOutput>(this string value, TOutput defaultValue) {
var type = typeof(TOutput);
var tryParseMethod = type.GetMethod("TryParse", BindingFlags.Static | BindingFlags.Public, Type.DefaultBinder,
new[] { typeof(string), type.MakeByRefType() }, null);
if (tryParseMethod == null) return defaultValue;
var arguments = new object[] { value, null };
return ((bool) tryParseMethod.Invoke(null, arguments)) ? (TOutput) arguments[1] : defaultValue;
}
This extension method lets you parse a string as any type that has a TryParse() method and it also lets you specify a default value to return if the conversion fails.
This is better than using the ternary operator with the extension method above as it only does the conversion once. It still uses reflection though...
Examples:
"123".ParseAs<int>(10);
"abc".ParseAs<int>(25);
"123,78".ParseAs<double>(10);
"abc".ParseAs<double>(107.4);
"2014-10-28".ParseAs<DateTime>(DateTime.MinValue);
"monday".ParseAs<DateTime>(DateTime.MinValue);
Outputs:
123
25
123,78
107,4
28.10.2014 00:00:00
01.01.0001 00:00:00

If you want to check if a string is a number (I'm assuming it's a string since if it's a number, duh, you know it's one).
Without regex and
using Microsoft's code as much as possible
you could also do:
public static bool IsNumber(this string aNumber)
{
BigInteger temp_big_int;
var is_number = BigInteger.TryParse(aNumber, out temp_big_int);
return is_number;
}
This will take care of the usual nasties:
Minus (-) or Plus (+) in the beginning
contains decimal character BigIntegers won't parse numbers with decimal points. (So: BigInteger.Parse("3.3") will throw an exception, and TryParse for the same will return false)
no funny non-digits
covers cases where the number is bigger than the usual use of Double.TryParse
You'll have to add a reference to System.Numerics and have
using System.Numerics; on top of your class (well, the second is a bonus I guess :)

Double.TryParse
bool Double.TryParse(string s, out double result)

The best flexible solution with .net built-in function called- char.IsDigit. It works with unlimited long numbers. It will only return true if each character is a numeric number. I used it lot of times with no issues and much easily cleaner solution I ever found. I made a example method.Its ready to use. In addition I added validation for null and empty input. So the method is now totally bulletproof
public static bool IsNumeric(string strNumber)
{
if (string.IsNullOrEmpty(strNumber))
{
return false;
}
else
{
int numberOfChar = strNumber.Count();
if (numberOfChar > 0)
{
bool r = strNumber.All(char.IsDigit);
return r;
}
else
{
return false;
}
}
}

Try the regex define below
new Regex(#"^\d{4}").IsMatch("6") // false
new Regex(#"^\d{4}").IsMatch("68ab") // false
new Regex(#"^\d{4}").IsMatch("1111abcdefg")
new Regex(#"^\d+").IsMatch("6") // true (any length but at least one digit)

With c# 7 it you can inline the out variable:
if(int.TryParse(str, out int v))
{
}

Use these extension methods to clearly distinguish between a check if the string is numerical and if the string only contains 0-9 digits
public static class ExtensionMethods
{
/// <summary>
/// Returns true if string could represent a valid number, including decimals and local culture symbols
/// </summary>
public static bool IsNumeric(this string s)
{
decimal d;
return decimal.TryParse(s, System.Globalization.NumberStyles.Any, System.Globalization.CultureInfo.CurrentCulture, out d);
}
/// <summary>
/// Returns true only if string is wholy comprised of numerical digits
/// </summary>
public static bool IsNumbersOnly(this string s)
{
if (s == null || s == string.Empty)
return false;
foreach (char c in s)
{
if (c < '0' || c > '9') // Avoid using .IsDigit or .IsNumeric as they will return true for other characters
return false;
}
return true;
}
}

public static bool IsNumeric(this string input)
{
int n;
if (!string.IsNullOrEmpty(input)) //.Replace('.',null).Replace(',',null)
{
foreach (var i in input)
{
if (!int.TryParse(i.ToString(), out n))
{
return false;
}
}
return true;
}
return false;
}

Regex rx = new Regex(#"^([1-9]\d*(\.)\d*|0?(\.)\d*[1-9]\d*|[1-9]\d*)$");
string text = "12.0";
var result = rx.IsMatch(text);
Console.WriteLine(result);
To check string is uint, ulong or contains only digits one .(dot) and digits
Sample inputs
123 => True
123.1 => True
0.123 => True
.123 => True
0.2 => True
3452.434.43=> False
2342f43.34 => False
svasad.324 => False
3215.afa => False

Hope this helps
string myString = "abc";
double num;
bool isNumber = double.TryParse(myString , out num);
if isNumber
{
//string is number
}
else
{
//string is not a number
}

Pull in a reference to Visual Basic in your project and use its Information.IsNumeric method such as shown below and be able to capture floats as well as integers unlike the answer above which only catches ints.
// Using Microsoft.VisualBasic;
var txt = "ABCDEFG";
if (Information.IsNumeric(txt))
Console.WriteLine ("Numeric");
IsNumeric("12.3"); // true
IsNumeric("1"); // true
IsNumeric("abc"); // false

All the Answers are Useful. But while searching for a solution where the Numeric value is 12 digits or more (in my case), then while debugging, I found the following solution useful :
double tempInt = 0;
bool result = double.TryParse("Your_12_Digit_Or_more_StringValue", out tempInt);
Th result variable will give you true or false.

Here is the C# method.
Int.TryParse Method (String, Int32)

bool is_number(string str, char delimiter = '.')
{
if(str.Length==0) //Empty
{
return false;
}
bool is_delimetered = false;
foreach (char c in str)
{
if ((c < '0' || c > '9') && (c != delimiter)) //ASCII table check. Not a digit && not delimeter
{
return false;
}
if (c == delimiter)
{
if (is_delimetered) //more than 1 delimiter
{
return false;
}
else //first time delimiter
{
is_delimetered = true;
}
}
}
return true;
}