Para conjuntos de enumerações de string maiores, os exemplos listados podem se tornar cansativos. Se você deseja uma lista de códigos de status ou outras enumerações baseadas em strings, um sistema de atributos é chato de usar e uma classe estática com instâncias próprias é chata de configurar. Para minha própria solução, utilizo o modelo T4 para facilitar a enumeração por string. O resultado é semelhante ao modo como a classe HttpMethod funciona.
Você pode usá-lo assim:
string statusCode = ResponseStatusCode.SUCCESS; // Automatically converts to string when needed
ResponseStatusCode codeByValueOf = ResponseStatusCode.ValueOf(statusCode); // Returns null if not found
// Implements TypeConverter so you can use it with string conversion methods.
var converter = System.ComponentModel.TypeDescriptor.GetConverter(typeof(ResponseStatusCode));
ResponseStatusCode code = (ResponseStatusCode) converter.ConvertFromInvariantString(statusCode);
// You can get a full list of the values
bool canIterateOverValues = ResponseStatusCode.Values.Any();
// Comparisons are by value of the "Name" property. Not by memory pointer location.
bool implementsByValueEqualsEqualsOperator = "SUCCESS" == ResponseStatusCode.SUCCESS;
Você começa com um arquivo Enum.tt.
<#@ include file="StringEnum.ttinclude" #>
<#+
public static class Configuration
{
public static readonly string Namespace = "YourName.Space";
public static readonly string EnumName = "ResponseStatusCode";
public static readonly bool IncludeComments = true;
public static readonly object Nodes = new
{
SUCCESS = "The response was successful.",
NON_SUCCESS = "The request was not successful.",
RESOURCE_IS_DISCONTINUED = "The resource requested has been discontinued and can no longer be accessed."
};
}
#>
Em seguida, você adiciona seu arquivo StringEnum.ttinclude.
<#@ template debug="false" hostspecific="false" language="C#" #>
<#@ assembly name="System.Core" #>
<#@ import namespace="System" #>
<#@ import namespace="System.Linq" #>
<#@ import namespace="System.Text" #>
<#@ import namespace="System.Reflection" #>
<#@ import namespace="System.Collections.Generic" #>
<#@ output extension=".cs" #>
<#@ CleanupBehavior processor="T4VSHost" CleanupAfterProcessingtemplate="true" #>
//------------------------------------------------------------------------------
// <auto-generated>
// This code was generated by a tool.
//
// Changes to this file may cause incorrect behavior and will be lost if
// the code is regenerated.
// </auto-generated>
//------------------------------------------------------------------------------
using System;
using System.Linq;
using System.Collections.Generic;
using System.ComponentModel;
using System.Globalization;
namespace <#= Configuration.Namespace #>
{
/// <summary>
/// TypeConverter implementations allow you to use features like string.ToNullable(T).
/// </summary>
public class <#= Configuration.EnumName #>TypeConverter : TypeConverter
{
public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
{
return sourceType == typeof(string) || base.CanConvertFrom(context, sourceType);
}
public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
{
var casted = value as string;
if (casted != null)
{
var result = <#= Configuration.EnumName #>.ValueOf(casted);
if (result != null)
{
return result;
}
}
return base.ConvertFrom(context, culture, value);
}
public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
{
var casted = value as <#= Configuration.EnumName #>;
if (casted != null && destinationType == typeof(string))
{
return casted.ToString();
}
return base.ConvertTo(context, culture, value, destinationType);
}
}
[TypeConverter(typeof(<#= Configuration.EnumName #>TypeConverter))]
public class <#= Configuration.EnumName #> : IEquatable<<#= Configuration.EnumName #>>
{
//---------------------------------------------------------------------------------------------------
// V A L U E S _ L I S T
//---------------------------------------------------------------------------------------------------
<# Write(Helpers.PrintEnumProperties(Configuration.Nodes)); #>
private static List<<#= Configuration.EnumName #>> _list { get; set; } = null;
public static List<<#= Configuration.EnumName #>> ToList()
{
if (_list == null)
{
_list = typeof(<#= Configuration.EnumName #>).GetFields().Where(x => x.IsStatic && x.IsPublic && x.FieldType == typeof(<#= Configuration.EnumName #>))
.Select(x => x.GetValue(null)).OfType<<#= Configuration.EnumName #>>().ToList();
}
return _list;
}
public static List<<#= Configuration.EnumName #>> Values()
{
return ToList();
}
/// <summary>
/// Returns the enum value based on the matching Name of the enum. Case-insensitive search.
/// </summary>
/// <param name="key"></param>
/// <returns></returns>
public static <#= Configuration.EnumName #> ValueOf(string key)
{
return ToList().FirstOrDefault(x => string.Compare(x.Name, key, true) == 0);
}
//---------------------------------------------------------------------------------------------------
// I N S T A N C E _ D E F I N I T I O N
//---------------------------------------------------------------------------------------------------
public string Name { get; private set; }
public string Description { get; private set; }
public override string ToString() { return this.Name; }
/// <summary>
/// Implcitly converts to string.
/// </summary>
/// <param name="d"></param>
public static implicit operator string(<#= Configuration.EnumName #> d)
{
return d.ToString();
}
/// <summary>
/// Compares based on the == method. Handles nulls gracefully.
/// </summary>
/// <param name="a"></param>
/// <param name="b"></param>
/// <returns></returns>
public static bool operator !=(<#= Configuration.EnumName #> a, <#= Configuration.EnumName #> b)
{
return !(a == b);
}
/// <summary>
/// Compares based on the .Equals method. Handles nulls gracefully.
/// </summary>
/// <param name="a"></param>
/// <param name="b"></param>
/// <returns></returns>
public static bool operator ==(<#= Configuration.EnumName #> a, <#= Configuration.EnumName #> b)
{
return a?.ToString() == b?.ToString();
}
/// <summary>
/// Compares based on the .ToString() method
/// </summary>
/// <param name="o"></param>
/// <returns></returns>
public override bool Equals(object o)
{
return this.ToString() == o?.ToString();
}
/// <summary>
/// Compares based on the .ToString() method
/// </summary>
/// <param name="other"></param>
/// <returns></returns>
public bool Equals(<#= Configuration.EnumName #> other)
{
return this.ToString() == other?.ToString();
}
/// <summary>
/// Compares based on the .Name property
/// </summary>
/// <returns></returns>
public override int GetHashCode()
{
return this.Name.GetHashCode();
}
}
}
<#+
public static class Helpers
{
public static string PrintEnumProperties(object nodes)
{
string o = "";
Type nodesTp = Configuration.Nodes.GetType();
PropertyInfo[] props = nodesTp.GetProperties().OrderBy(p => p.Name).ToArray();
for(int i = 0; i < props.Length; i++)
{
var prop = props[i];
if (Configuration.IncludeComments)
{
o += "\r\n\r\n";
o += "\r\n ///<summary>";
o += "\r\n /// "+Helpers.PrintPropertyValue(prop, Configuration.Nodes);
o += "\r\n ///</summary>";
}
o += "\r\n public static readonly "+Configuration.EnumName+" "+prop.Name+ " = new "+Configuration.EnumName+"(){ Name = \""+prop.Name+"\", Description = "+Helpers.PrintPropertyValue(prop, Configuration.Nodes)+ "};";
}
o += "\r\n\r\n";
return o;
}
private static Dictionary<string, string> GetValuesMap()
{
Type nodesTp = Configuration.Nodes.GetType();
PropertyInfo[] props= nodesTp.GetProperties();
var dic = new Dictionary<string,string>();
for(int i = 0; i < props.Length; i++)
{
var prop = nodesTp.GetProperties()[i];
dic[prop.Name] = prop.GetValue(Configuration.Nodes).ToString();
}
return dic;
}
public static string PrintMasterValuesMap(object nodes)
{
Type nodesTp = Configuration.Nodes.GetType();
PropertyInfo[] props= nodesTp.GetProperties();
string o = " private static readonly Dictionary<string, string> ValuesMap = new Dictionary<string, string>()\r\n {";
for(int i = 0; i < props.Length; i++)
{
var prop = nodesTp.GetProperties()[i];
o += "\r\n { \""+prop.Name+"\", "+(Helpers.PrintPropertyValue(prop,Configuration.Nodes)+" },");
}
o += ("\r\n };\r\n");
return o;
}
public static string PrintPropertyValue(PropertyInfo prop, object objInstance)
{
switch(prop.PropertyType.ToString()){
case "System.Double":
return prop.GetValue(objInstance).ToString()+"D";
case "System.Float":
return prop.GetValue(objInstance).ToString()+"F";
case "System.Decimal":
return prop.GetValue(objInstance).ToString()+"M";
case "System.Long":
return prop.GetValue(objInstance).ToString()+"L";
case "System.Boolean":
case "System.Int16":
case "System.Int32":
return prop.GetValue(objInstance).ToString().ToLowerInvariant();
case "System.String":
return "\""+prop.GetValue(objInstance)+"\"";
}
return prop.GetValue(objInstance).ToString();
}
public static string _ (int numSpaces)
{
string o = "";
for(int i = 0; i < numSpaces; i++){
o += " ";
}
return o;
}
}
#>
Por fim, você recompila o arquivo Enum.tt e a saída fica assim:
//------------------------------------------------------------------------------
// <auto-generated>
// This code was generated by a tool.
//
// Changes to this file may cause incorrect behavior and will be lost if
// the code is regenerated.
// </auto-generated>
//------------------------------------------------------------------------------
using System;
using System.Linq;
using System.Collections.Generic;
namespace YourName.Space
{
public class ResponseStatusCode
{
//---------------------------------------------------------------------------------------------------
// V A L U E S _ L I S T
//---------------------------------------------------------------------------------------------------
///<summary>
/// "The response was successful."
///</summary>
public static readonly ResponseStatusCode SUCCESS = new ResponseStatusCode(){ Name = "SUCCESS", Description = "The response was successful."};
///<summary>
/// "The request was not successful."
///</summary>
public static readonly ResponseStatusCode NON_SUCCESS = new ResponseStatusCode(){ Name = "NON_SUCCESS", Description = "The request was not successful."};
///<summary>
/// "The resource requested has been discontinued and can no longer be accessed."
///</summary>
public static readonly ResponseStatusCode RESOURCE_IS_DISCONTINUED = new ResponseStatusCode(){ Name = "RESOURCE_IS_DISCONTINUED", Description = "The resource requested has been discontinued and can no longer be accessed."};
private static List<ResponseStatusCode> _list { get; set; } = null;
public static List<ResponseStatusCode> ToList()
{
if (_list == null)
{
_list = typeof(ResponseStatusCode).GetFields().Where(x => x.IsStatic && x.IsPublic && x.FieldType == typeof(ResponseStatusCode))
.Select(x => x.GetValue(null)).OfType<ResponseStatusCode>().ToList();
}
return _list;
}
public static List<ResponseStatusCode> Values()
{
return ToList();
}
/// <summary>
/// Returns the enum value based on the matching Name of the enum. Case-insensitive search.
/// </summary>
/// <param name="key"></param>
/// <returns></returns>
public static ResponseStatusCode ValueOf(string key)
{
return ToList().FirstOrDefault(x => string.Compare(x.Name, key, true) == 0);
}
//---------------------------------------------------------------------------------------------------
// I N S T A N C E _ D E F I N I T I O N
//---------------------------------------------------------------------------------------------------
public string Name { get; set; }
public string Description { get; set; }
public override string ToString() { return this.Name; }
/// <summary>
/// Implcitly converts to string.
/// </summary>
/// <param name="d"></param>
public static implicit operator string(ResponseStatusCode d)
{
return d.ToString();
}
/// <summary>
/// Compares based on the == method. Handles nulls gracefully.
/// </summary>
/// <param name="a"></param>
/// <param name="b"></param>
/// <returns></returns>
public static bool operator !=(ResponseStatusCode a, ResponseStatusCode b)
{
return !(a == b);
}
/// <summary>
/// Compares based on the .Equals method. Handles nulls gracefully.
/// </summary>
/// <param name="a"></param>
/// <param name="b"></param>
/// <returns></returns>
public static bool operator ==(ResponseStatusCode a, ResponseStatusCode b)
{
return a?.ToString() == b?.ToString();
}
/// <summary>
/// Compares based on the .ToString() method
/// </summary>
/// <param name="o"></param>
/// <returns></returns>
public override bool Equals(object o)
{
return this.ToString() == o?.ToString();
}
/// <summary>
/// Compares based on the .Name property
/// </summary>
/// <returns></returns>
public override int GetHashCode()
{
return this.Name.GetHashCode();
}
}
}