Generic EnumHelper Class for C#
By
Steve on
Monday, May 28, 2018
Updated
Sunday, September 13, 2020
Viewed
27,259 times. (
3 times today.)
Summary
Enums in C# are very useful, but it can seem difficult to work with them at times. In truth, they're pretty easy, but a generic helper class can make our lives a lot easier.
Generic EnumHelper Class
#region CambiaResearch.com (MIT License)
// Author: Steve Lautenschlager, https://www.cambiaresearch.com
// License: MIT. https://opensource.org/licenses/MIT
#endregion
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Globalization;
using System.Reflection;
namespace Cambia.CoreLib
{
public class EnumHelper
{
public static T FromDisplayName<T>(string displayName) where T : struct, IConvertible
{
List<T> items = GetItems<T>(false);
// Check for a display name match
foreach (T item in items)
{
string itemDisplayName = GetEnumDisplayName(item as Enum);
if (itemDisplayName == displayName)
{
return item;
}
}
// Check for a ordinary name match
foreach (T item in items)
{
if (item.ToString() == displayName)
{
return item;
}
}
return GetDefault<T>();
}
public static T GetDefault<T>()
{
if (IsDefined<T>("None"))
{
return (T)Enum.Parse(typeof(T), "None", true);
}
else if (IsDefined<T>(0))
{
return (T)Enum.ToObject(typeof(T), 0);
}
else
{
throw new ArgumentException("No default value found for type " + typeof(T).FullName);
}
}
/// <summary>
/// Define the enum description as follows and the specified description attribute is what will get returned from
/// this method, otherwise, just the text of the enum name itself.
///
/// public enum MyEnum
/// {
/// [Description("Empty")]
/// None,
/// [Description("First Item")]
/// Item1,
/// [Description("Second Item")]
/// Item2
/// }
/// </summary>
public static string GetEnumDescription(Enum value)
{
FieldInfo fi = value.GetType().GetField(value.ToString());
DescriptionAttribute[] attributes = (DescriptionAttribute[])fi.GetCustomAttributes(typeof(DescriptionAttribute), false);
if (attributes != null && attributes.Length > 0)
{
return attributes[0].Description;
}
else
{
return value.ToString();
}
}
/// <summary>
/// Define the enum display name as follows.
///
/// public enum MyEnum
/// {
/// [Display(Name = "None")]
/// None,
/// [Display(Name = "Item1")]
/// Item1,
/// [Display(Name = "Item2")]
/// Item2
/// }
/// </summary>
public static string GetEnumDisplayName(Enum value)
{
DisplayAttribute att = value.GetAttribute<DisplayAttribute>();
if (att != null)
{
return att.Name;
}
else
{
return value.ToString();
}
}
public static List<object> GetItems(Type enumType, bool excludeNone = false)
{
if (!enumType.IsEnum)
{
throw new ArgumentException("Type must be an enum type.");
}
int noneValue = -1;
if (excludeNone)
{
noneValue = GetNoneValue(enumType);
}
int[] items = (int[])Enum.GetValues(enumType);
List<object> output = new List<object>();
foreach (int val in items)
{
if (noneValue > -1 && noneValue == val) { continue; }
output.Add(val);
}
return output;
}
/// <summary>
/// Gets a list of all instances of enum items within the specified enum.
/// </summary>
public static List<T> GetItems<T>(bool excludeNone = false) where T : struct, IConvertible
{
if (!typeof(T).IsEnum)
{
throw new ArgumentException("T must be an enum type.");
}
int noneValue = -1;
if (excludeNone)
{
noneValue = GetNoneValue<T>();
}
List<T> list = new List<T>();
foreach (T value in Enum.GetValues(typeof(T)))
{
if (noneValue > -1 && noneValue == GetValue<T>(value)) { continue; }
list.Add(value);
}
//if (excludeNone)
//{
// if (Enum.TryParse("None", true, out T noneValue))
// {
// list.Remove(noneValue);
// }
//}
return list;
}
public static int GetNoneValue<T>() where T : struct, IConvertible
{
if (!typeof(T).IsEnum)
{
throw new ArgumentException("T must be an enum type.");
}
if (Enum.TryParse("None", true, out T noneValue))
{
return GetValue<T>(noneValue);
}
else
{
return -1;
}
}
public static int GetNoneValue(Type enumType)
{
if (!enumType.IsEnum)
{
throw new ArgumentException("Type must be an enum type.");
}
string[] names = Enum.GetNames(enumType);
int indexOfNone = -1;
for (int i = 0; i < names.Length; i++)
{
if (names[i] == "None")
{
indexOfNone = i;
break;
}
}
if (indexOfNone > -1)
{
int[] values = (int[])Enum.GetValues(enumType);
return values[indexOfNone];
}
else
{
return -1;
}
}
public static int GetValue<T>(T value) where T : struct, IConvertible
{
Type t = typeof(T);
if (!t.IsEnum)
{
throw new ArgumentException("T must be an enum type.");
}
return value.ToInt32(CultureInfo.InvariantCulture.NumberFormat);
}
public static int GetValue(object enumValue)
{
Type t = enumValue.GetType();
if (!t.IsEnum)
{
throw new ArgumentException("T must be an enum type.");
}
return ((IConvertible)enumValue).ToInt32(CultureInfo.InvariantCulture.NumberFormat);
}
public static List<int> GetValues(Type enumType, bool excludeNone = false)
{
int noneValue = -1;
if (excludeNone) { noneValue = GetNoneValue(enumType); }
Array items = Enum.GetValues(enumType);
List<int> intValues = new List<int>();
foreach (var en in items)
{
if (excludeNone && (int)en == noneValue)
{
continue;
}
intValues.Add((int)en);
}
return intValues;
}
public static List<int> GetValues<T>(bool excludeNone = false)
{
return GetValues(typeof(T), excludeNone);
}
/// <summary>
/// Gets a sorted dictionary of the integer and string representations of each item in the enumeration. The
/// keys are integers and the values are strings.
/// </summary>
public static SortedDictionary<int, string> GetValues<T>() where T : struct, IConvertible
{
if (!typeof(T).IsEnum)
{
throw new ArgumentException("T must be an enum type.");
}
SortedDictionary<int, string> sortedList = new SortedDictionary<int, string>();
Type enumType = typeof(T);
foreach (T value in Enum.GetValues(enumType))
{
FieldInfo fi = enumType.GetField(value.ToString());
DescriptionAttribute[] attributes = (DescriptionAttribute[])fi.GetCustomAttributes(typeof(DescriptionAttribute), false);
if (attributes != null && attributes.Length > 0)
{
DescriptionAttribute description = (DescriptionAttribute)attributes[0];
sortedList.Add(value.ToInt32(CultureInfo.CurrentCulture.NumberFormat), description.Description);
}
else
{
sortedList.Add(value.ToInt32(CultureInfo.CurrentCulture.NumberFormat), value.ToString());
}
}
return sortedList;
}
public static bool IsDefined<T>(string strEnumText)
{
string s = strEnumText.Trim().ToUpper();
string[] names = Enum.GetNames(typeof(T));
foreach (string n in names)
{
if (n.ToUpper() == s)
{
return true;
}
}
return false;
}
public static bool IsDefined<T>(int iEnumValue)
{
int[] vals = (int[])Enum.GetValues(typeof(T));
foreach (int i in vals)
{
if (iEnumValue == i)
{
return true;
}
}
return false;
}
/// <summary>
/// Returns default if it can't parse. If no default found, then
/// throws exception.
/// </summary>
public static T Parse<T>(int iEnumValue)
{
if (IsDefined<T>(iEnumValue))
{
T rt = (T)Enum.ToObject(typeof(T), iEnumValue);
return rt;
}
else
{
return GetDefault<T>();
}
}
/// <summary>
/// Returns default if it can't parse. If no default found, then
/// throws exception.
/// </summary>
public static T Parse<T>(string strEnumText) where T : struct
{
if (IsDefined<T>(strEnumText))
{
T pm = (T)Enum.Parse(typeof(T), strEnumText, true);
return pm;
}
else
{
return GetDefault<T>();
}
}
public static bool TryParse(Type enumType, string value, out object objectEnum)
{
objectEnum = null;
try
{
objectEnum = Enum.Parse(enumType, value);
return true;
}
catch
{
return false;
}
}
public static bool TryParse<T>(string text, out T enumValue) where T : struct
{
if (IsDefined<T>(text))
{
enumValue = (T)Enum.Parse(typeof(T), text, true);
return true;
}
else
{
enumValue = GetDefault<T>();
return false;
}
}
}
}
Bonus: FlagsHelper class
You can add these methods to the EnumHelper if you like. I like to keep them separate in the FlagsHelper class.
That has its downside. I find myself looking for them in the EnumHelper and wondering why they're not there.
#region CambiaResearch.com (MIT License)
// Author: Steve Lautenschlager, https://www.cambiaresearch.com
// License: MIT. https://opensource.org/licenses/MIT
#endregion
public static class FlagsHelper
{
public static bool IsSet<T>(T flags, T flag) where T : struct
{
int flagsValue = (int)(object)flags;
int flagValue = (int)(object)flag;
return (flagsValue & flagValue) == flagValue;
}
public static void Set<T>(ref T flags, T flag) where T : struct
{
int flagsValue = (int)(object)flags;
int flagValue = (int)(object)flag;
flags = (T)(object)(flagsValue | flagValue);
}
public static void Unset<T>(ref T flags, T flag) where T : struct
{
int flagsValue = (int)(object)flags;
int flagValue = (int)(object)flag;
flags = (T)(object)(flagsValue & (~flagValue));
}
}