blocks|key|1414951|text|enum+(实际上是任何值类型)的默认值是0+--即使这不是该enum的有效值。它不能更改。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1414952|entityMap^0|0|4|V|4|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

The default for an <code>enum</code> (in fact, any value type) is 0 -- even if that is not a valid value for that <code>enum</code>. It cannot be changed.

blocks|key|1629730|text|枚举的默认值是枚举等于零的任何值。我不相信这是可以通过属性或其他方式改变的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1629731|(MSDN说：“枚举E的默认值是表达式(E)0产生的值。”)|1629732|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

An enum's default is whatever enumeration equates to zero. I don't believe this is changeable by attribute or other means.

(MSDN says: "The default value of an enum E is the value produced by the expression (E)0.")

blocks|key|1629768|text|实际上，enum的默认值是enum中值为0的第一个元素。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1629769|举个例子：|1629770|public+enum+Animals
{
++++Cat,
++++Dog,
++++Pony+=+0,
}
//its+value+will+actually+be+Cat+not+Pony+unless+you+assign+a+non+zero+value+to+Cat.
Animals+animal;|code-block|syntax|javascript|1629771|entityMap^0|4|4|D|4|K|1|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|V|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|W|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|X|8|@]|D|@]|E|$]]]|N|$]]

Actually an <code>enum</code>'s default is the first element in the <code>enum</code> whose value is <code>0</code>.

So for example:

<pre><code>public enum Animals
{
 Cat,
 Dog,
 Pony = 0,
}
//its value will actually be Cat not Pony unless you assign a non zero value to Cat.
Animals animal;
</code></pre>

blocks|key|1415101|text|你不能，但如果你想，你可以做一些小把戏。:)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1415102|++++public+struct+Orientation
++++{
++++++++...
++++++++public+static+Orientation+None+=+-1;
++++++++public+static+Orientation+North+=+0;
++++++++public+static+Orientation+East+=+1;
++++++++public+static+Orientation+South+=+2;
++++++++public+static+Orientation+West+=+3;
++++}|code-block|syntax|javascript|1415103|将此结构用作简单的枚举。|1415104|默认情况下，您可以在其中创建p.a+==+Orientation.East+(或所需的任何值|1415105|要使用技巧本身，您需要通过代码从int转换。|1415106|这就是实现：|1415107|++++++++#region+ConvertingToEnum
++++++++private+int+val;
++++++++static+Dictionary<int,+string>+dict+=+null;

++++++++public+Orientation(int+val)
++++++++{
++++++++++++this.val+=+val;
++++++++}

++++++++public+static+implicit+operator+Orientation(int+value)
++++++++{
++++++++++++return+new+Orientation(value+-+1);
++++++++}

++++++++public+static+bool+operator+==(Orientation+a,+Orientation+b)
++++++++{
++++++++++++return+a.val+==+b.val;
++++++++}

++++++++public+static+bool+operator+!=(Orientation+a,+Orientation+b)
++++++++{
++++++++++++return+a.val+!=+b.val;
++++++++}

++++++++public+override+string+ToString()
++++++++{
++++++++++++if+(dict+==+null)
++++++++++++++++InitializeDict();
++++++++++++if+(dict.ContainsKey(val))
++++++++++++++++return+dict[val];
++++++++++++return+val.ToString();
++++++++}

++++++++private+void+InitializeDict()
++++++++{
++++++++++++dict+=+new+Dictionary<int,+string>();
++++++++++++foreach+(var+fields+in+GetType().GetFields(BindingFlags.Public+%7C+BindingFlags.Static))
++++++++++++{
++++++++++++++++dict.Add(((Orientation)fields.GetValue(null)).val,+fields.Name);
++++++++++++}
++++++++}+
++++++++#endregion|1415108|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|Y|8|@]|9|@]|A|$E|F]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

You can't, but if you want, you can do some trick. :) 

<pre><code> public struct Orientation
 {
 ...
 public static Orientation None = -1;
 public static Orientation North = 0;
 public static Orientation East = 1;
 public static Orientation South = 2;
 public static Orientation West = 3;
 }
</code></pre>

usage of this struct as simple enum. 
where you can create p.a == Orientation.East (or any value that you want) by default 
to use the trick itself, you need to convert from int by code. 
there the implementation:

<pre><code> #region ConvertingToEnum
 private int val;
 static Dictionary&lt;int, string&gt; dict = null;

 public Orientation(int val)
 {
 this.val = val;
 }

 public static implicit operator Orientation(int value)
 {
 return new Orientation(value - 1);
 }

 public static bool operator ==(Orientation a, Orientation b)
 {
 return a.val == b.val;
 }

 public static bool operator !=(Orientation a, Orientation b)
 {
 return a.val != b.val;
 }

 public override string ToString()
 {
 if (dict == null)
 InitializeDict();
 if (dict.ContainsKey(val))
 return dict[val];
 return val.ToString();
 }

 private void InitializeDict()
 {
 dict = new Dictionary&lt;int, string&gt;();
 foreach (var fields in GetType().GetFields(BindingFlags.Public | BindingFlags.Static))
 {
 dict.Add(((Orientation)fields.GetValue(null)).val, fields.Name);
 }
 } 
 #endregion
</code></pre>

blocks|key|1629911|text|任何枚举的默认值都是零。因此，如果要将一个枚举器设置为默认值，则将该枚举器设置为零，并将所有其他枚举器设置为非零(如果有多个枚举器的值为零，则第一个值为零的枚举器将成为该枚举的默认值)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1629912|enum+Orientation
{
++++None+=+0,+//default+value+since+it+has+the+value+'0'
++++North+=+1,
++++East+=+2,
++++South+=+3,
++++West+=+4
}

Orientation+o;+//+initialized+to+'None'|code-block|syntax|javascript|1629913|如果您的枚举器不需要显式的值，那么只需确保第一个枚举器是您希望成为默认枚举器的枚举器，因为“默认情况下，第一个枚举器的值为0，并且每个后续枚举器的值都加1。”(C#+reference)|offset|length|1629914|enum+Orientation
{
++++None,+//default+value+since+it+is+the+first+enumerator
++++North,
++++East,
++++South,
++++West
}

Orientation+o;+//+initialized+to+'None'|1629915|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/sbbt4032.aspx^0|0|0|28|C|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@]|9|@$I|X|J|Y|1|Z]]|A|$]]|$1|K|3|L|5|D|7|10|8|@]|9|@]|A|$E|F]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]]]

The default value of any enum is zero. So if you want to set one enumerator to be the default value, then set that one to zero and all other enumerators to non-zero (the first enumerator to have the value zero will be the default value for that enum if there are several enumerators with the value zero).

<pre><code>enum Orientation
{
 None = 0, //default value since it has the value '0'
 North = 1,
 East = 2,
 South = 3,
 West = 4
}

Orientation o; // initialized to 'None'
</code></pre>

If your enumerators don't need explicit values, then just make sure the first enumerator is the one you want to be the default enumerator since "By default, the first enumerator has the value 0, and the value of each successive enumerator is increased by 1." (<a href="http://msdn.microsoft.com/en-us/library/sbbt4032.aspx" rel="noreferrer">C# reference</a>)

<pre><code>enum Orientation
{
 None, //default value since it is the first enumerator
 North,
 East,
 South,
 West
}

Orientation o; // initialized to 'None'
</code></pre>

blocks|key|1629964|text|[DefaultValue(None)]
public+enum+Orientation
{
++++None+=+-1,
++++North+=+0,
++++East+=+1,
++++South+=+2,
++++West+=+3
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1629965|然后，在代码中您可以使用|unstyled|1629966|public+Orientation+GetDefaultOrientation()
{
+++return+default(Orientation);
}+|1629967|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|L|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|I|3|-4|5|F|7|N|8|@]|9|@]|A|$]]]|J|$]]

<pre><code>[DefaultValue(None)]
public enum Orientation
{
 None = -1,
 North = 0,
 East = 1,
 South = 2,
 West = 3
}
</code></pre>

Then in the code you can use 

<pre><code>public Orientation GetDefaultOrientation()
{
 return default(Orientation);
} 
</code></pre>

blocks|key|1630003|text|默认值为定义中的第一个。例如：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1630004|public+enum+MyEnum{His,Hers,Mine,Theirs}

Enum.GetValues(typeOf(MyEnum)).GetValue(0);|code-block|syntax|javascript|1630005|这将返回His|offset|length|style|CODE|1630006|entityMap^0|0|0|4|3|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

The default is the first one in the definition. For example:

<pre><code>public enum MyEnum{His,Hers,Mine,Theirs}

Enum.GetValues(typeOf(MyEnum)).GetValue(0);
</code></pre>

This will return <code>His</code>

blocks|key|1415375|text|如果0不是合适的默认值，您可以使用组件模型来定义枚举的解决方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1415376|[DefaultValue(None)]
public+enum+Orientation
{
+++++None+=+-1,
+++++North+=+0,
+++++East+=+1,
+++++South+=+2,
+++++West+=+3
+}

public+static+class+Utilities
{
++++public+static+TEnum+GetDefaultValue<TEnum>()+where+TEnum+:+struct
++++{
++++++++Type+t+=+typeof(TEnum);
++++++++DefaultValueAttribute[]+attributes+=+(DefaultValueAttribute[])t.GetCustomAttributes(typeof(DefaultValueAttribute),+false);
++++++++if+(attributes+!=+null+&&
++++++++++++attributes.Length+>+0)
++++++++{
++++++++++++return+(TEnum)attributes[0].Value;
++++++++}
++++++++else
++++++++{
++++++++++++return+default(TEnum);
++++++++}
++++}
}|code-block|syntax|javascript|1415377|然后你可以调用：|1415378|Orientation+o+=+Utilities.GetDefaultValue<Orientation>();
System.Diagnostics.Debug.Print(o.ToString());|1415379|注意:您需要在文件的顶部包含以下行：|1415380|using+System.ComponentModel;|1415381|这不会更改枚举的实际C#语言缺省值，但提供了一种指示(和获取)所需缺省值的方法。|1415382|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

If zero doesn't work as the proper default value, you can use the component model to define a workaround for the enum:

<pre><code>[DefaultValue(None)]
public enum Orientation
{
 None = -1,
 North = 0,
 East = 1,
 South = 2,
 West = 3
 }

public static class Utilities
{
 public static TEnum GetDefaultValue&lt;TEnum&gt;() where TEnum : struct
 {
 Type t = typeof(TEnum);
 DefaultValueAttribute[] attributes = (DefaultValueAttribute[])t.GetCustomAttributes(typeof(DefaultValueAttribute), false);
 if (attributes != null &amp;&amp;
 attributes.Length &gt; 0)
 {
 return (TEnum)attributes[0].Value;
 }
 else
 {
 return default(TEnum);
 }
 }
}
</code></pre>

and then you can call:

<pre><code>Orientation o = Utilities.GetDefaultValue&lt;Orientation&gt;();
System.Diagnostics.Debug.Print(o.ToString());
</code></pre>

Note: you will need to include the following line at the top of the file:

<pre><code>using System.ComponentModel;
</code></pre>

This does not change the actual C# language default value of the enum, but gives a way to indicate (and get) the desired default value.

blocks|key|1415411|text|另一种可能有用的方法--使用某种“别名”。例如：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1415412|public+enum+Status
{
++++New+=+10,
++++Old+=+20,
++++Actual+=+30,

++++//+Use+Status.Default+to+specify+default+status+in+your+code.+
++++Default+=+New+
}|code-block|syntax|javascript|1415413|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

One more way that might be helpful - to use some kind of "alias".
For example:

<pre><code>public enum Status
{
 New = 10,
 Old = 20,
 Actual = 30,

 // Use Status.Default to specify default status in your code. 
 Default = New 
}
</code></pre>

blocks|key|1630158|text|The+default+value+of+enum+is+the+enummember+equal+to+0+or+the+first+element(if+value+is+not+specified)+...但是我在我的项目中遇到了使用enum的关键问题，并通过执行以下操作来克服这些问题……我的需求是如何与类级别相关的.|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1630159|++++class+CDDtype
++++{
++++++++public+int+Id+{+get;+set;+}
++++++++public+DDType+DDType+{+get;+set;+}

++++++++public+CDDtype()
++++++++{
++++++++++++DDType+=+DDType.None;
++++++++}
++++}++++


++++[DefaultValue(None)]
++++public+enum+DDType
++++{+++++++
++++++++None+=+-1,+++++++
++++++++ON+=+0,+++++++
++++++++FC+=+1,+++++++
++++++++NC+=+2,+++++++
++++++++CC+=+3
++++}|code-block|syntax|javascript|1630160|并获得预期的结果|1630161|++++CDDtype+d1=+new+CDDtype();
++++CDDtype+d2+=+new+CDDtype+{+Id+=+50+};

++++Console.Write(d1.DDType);//None
++++Console.Write(d2.DDType);//None|1630162|现在，如果值来自DB……好的，在这个场景中...在下面的函数中传递值，它会将值转换为处理各种情况的枚举...below函数，并且它是通用的。相信我，这是非常快的……:)|1630163|++++public+static+T+ToEnum<T>(this+object+value)
++++{
++++++++//Checking+value+is+null+or+DBNull
++++++++if+(!value.IsNull())
++++++++{
++++++++++++return+(T)Enum.Parse(typeof(T),+value.ToStringX());
++++++++}

++++++++//Returanable+object
++++++++object+ValueToReturn+=+null;

++++++++//First+checking+whether+any+'DefaultValueAttribute'+is+present+or+not
++++++++var+DefaultAtt+=+(from+a+in+typeof(T).CustomAttributes
++++++++++++++++++++++++++where+a.AttributeType+==+typeof(DefaultValueAttribute)
++++++++++++++++++++++++++select+a).FirstOrNull();

++++++++//If+DefaultAttributeValue+is+present
++++++++if+((!DefaultAtt.IsNull())+&&+(DefaultAtt.ConstructorArguments.Count+==+1))
++++++++{
++++++++++++ValueToReturn+=+DefaultAtt.ConstructorArguments[0].Value;
++++++++}

++++++++//If+still+no+value+found
++++++++if+(ValueToReturn.IsNull())
++++++++{
++++++++++++//Trying+to+get+the+very+first+property+of+that+enum
++++++++++++Array+Values+=+Enum.GetValues(typeof(T));

++++++++++++//getting+very+first+member+of+this+enum
++++++++++++if+(Values.Length+>+0)
++++++++++++{
++++++++++++++++ValueToReturn+=+Values.GetValue(0);
++++++++++++}
++++++++}

++++++++//If+any+result+found
++++++++if+(!ValueToReturn.IsNull())
++++++++{
++++++++++++return+(T)Enum.Parse(typeof(T),+ValueToReturn.ToStringX());
++++++++}

++++++++return+default(T);
++++}|1630164|entityMap^0|0|2U|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|Y|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|10|8|@]|D|@]|E|$]]|$1|Q|3|R|5|H|7|11|8|@]|D|@]|E|$I|J]]|$1|S|3|-4|5|6|7|12|8|@]|D|@]|E|$]]]|T|$]]

<code>The default value of enum is the enummember equal to 0 or the first element(if value is not specified)</code> ... But i have faced critical problems using enum in my projects and overcome by doing something below ... How ever my need was related to class level ...

<pre><code> class CDDtype
 {
 public int Id { get; set; }
 public DDType DDType { get; set; }

 public CDDtype()
 {
 DDType = DDType.None;
 }
 } 


 [DefaultValue(None)]
 public enum DDType
 { 
 None = -1, 
 ON = 0, 
 FC = 1, 
 NC = 2, 
 CC = 3
 }
</code></pre>

and get expected result

<pre><code> CDDtype d1= new CDDtype();
 CDDtype d2 = new CDDtype { Id = 50 };

 Console.Write(d1.DDType);//None
 Console.Write(d2.DDType);//None
</code></pre>

Now what if value is coming from DB .... Ok in this scenario... pass value in below function and it will convertthe value to enum ...below function handled various scenario and it's generic... and believe me it is very fast ..... :)

<pre><code> public static T ToEnum&lt;T&gt;(this object value)
 {
 //Checking value is null or DBNull
 if (!value.IsNull())
 {
 return (T)Enum.Parse(typeof(T), value.ToStringX());
 }

 //Returanable object
 object ValueToReturn = null;

 //First checking whether any 'DefaultValueAttribute' is present or not
 var DefaultAtt = (from a in typeof(T).CustomAttributes
 where a.AttributeType == typeof(DefaultValueAttribute)
 select a).FirstOrNull();

 //If DefaultAttributeValue is present
 if ((!DefaultAtt.IsNull()) &amp;&amp; (DefaultAtt.ConstructorArguments.Count == 1))
 {
 ValueToReturn = DefaultAtt.ConstructorArguments[0].Value;
 }

 //If still no value found
 if (ValueToReturn.IsNull())
 {
 //Trying to get the very first property of that enum
 Array Values = Enum.GetValues(typeof(T));

 //getting very first member of this enum
 if (Values.Length &gt; 0)
 {
 ValueToReturn = Values.GetValue(0);
 }
 }

 //If any result found
 if (!ValueToReturn.IsNull())
 {
 return (T)Enum.Parse(typeof(T), ValueToReturn.ToStringX());
 }

 return default(T);
 }
</code></pre>

blocks|key|1415515|text|如果将默认枚举定义为具有最小值的枚举，则可以使用以下命令：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1415516|public+enum+MyEnum+{+His+=+-1,+Hers+=+-2,+Mine+=+-4,+Theirs+=+-3+}

var+firstEnum+=+((MyEnum[])Enum.GetValues(typeof(MyEnum)))[0];

firstEnum+==+Mine.|code-block|syntax|javascript|1415517|这并不假设枚举的值为零。|1415518|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

If you define the Default enum as the enum with the smallest value you can use this:

<pre><code>public enum MyEnum { His = -1, Hers = -2, Mine = -4, Theirs = -3 }

var firstEnum = ((MyEnum[])Enum.GetValues(typeof(MyEnum)))[0];

firstEnum == Mine.
</code></pre>

This doesn't assume that the enum has a zero value.

blocks|key|1630265|text|enum+Orientations
{
++++None,+North,+East,+South,+West
}
private+Orientations?+_orientation+{+get;+set;+}

public+Orientations?+Orientation
{
++++get
++++{
++++++++return+_orientation+??+Orientations.None;
++++}
++++set
++++{
++++++++_orientation+=+value;
++++}
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1630266|如果将该属性设置为null，则get时将返回Orientations.None。默认情况下，属性_orientation为null。|unstyled|1630267|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>enum Orientations
{
 None, North, East, South, West
}
private Orientations? _orientation { get; set; }

public Orientations? Orientation
{
 get
 {
 return _orientation ?? Orientations.None;
 }
 set
 {
 _orientation = value;
 }
}
</code></pre>

If you set the property to null will return Orientations.None on get.
The property _orientation is null by default.

blocks|key|1630366|text|在这种情况下，不要依赖枚举值。将None设为0作为默认值。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1630367|//+Remove+all+the+values+from+the+enum
enum+Orientation
{
++++None,+//+=+0+Putting+None+as+the+first+enum+value+will+make+it+the+default
++++North,+//+=+1
++++East,+//+=+2
++++South,+//+=+3
++++West+//+=+4
}|code-block|syntax|javascript|1630368|然后使用一个方法来获取Magic+Number。您可以引入一个Extension+Method并像这样使用它：|1630369|//+Extension+Methods+are+added+by+adding+a+using+to+the+namespace
using+ProjectName.Extensions;

Orientation.North.ToMagicNumber();|1630370|下面是代码：|1630371|namespace+ProjectName.Extensions
{
++++public+static+class+OrientationExtensions+
++++{
++++++++public+static+int+ToMagicNumber(this+Orientation+orientation)+=>+oritentation+switch
++++++++{
++++++++++++case+None++=>+-1,
++++++++++++case+North+=>+0,
++++++++++++case+East++=>+1,
++++++++++++case+South+=>+2,
++++++++++++case+West++=>+3,
++++++++++++_++++++++++=>+throw+new+ArgumentOutOfRangeException(nameof(orientation),+$"Not+expected+orientation+value:+{orientation}")
++++++++};
++++}
}|1630372|entityMap|0|LINK|mutability|MUTABLE|url|https://en.wikipedia.org/wiki/Magic_number_(programming))|1|https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/extension-methods^0|G|4|M|1|0|0|B|C|0|V|G|1|0|0|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|17|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|18|8|@]|D|@$9|19|A|1A|1|1B]|$9|1C|A|1D|1|1E]]|E|$]]|$1|M|3|N|5|H|7|1F|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|1G|8|@]|D|@]|E|$]]|$1|Q|3|R|5|H|7|1H|8|@]|D|@]|E|$I|J]]|$1|S|3|-4|5|6|7|1I|8|@]|D|@]|E|$]]]|T|$U|$5|V|W|X|E|$Y|Z]]|10|$5|V|W|X|E|$Y|11]]]]

Don't rely on the enum value in this case. Let <code>None</code> be <code>0</code> as a default.
<pre><code>// Remove all the values from the enum
enum Orientation
{
 None, // = 0 Putting None as the first enum value will make it the default
 North, // = 1
 East, // = 2
 South, // = 3
 West // = 4
}
</code></pre>
Then use a method to get the <a href="https://en.wikipedia.org/wiki/Magic_number_(programming)" rel="nofollow noreferrer">Magic Number</a>. You can introduce an <a href="https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/extension-methods" rel="nofollow noreferrer">Extension Method</a> and use it like:
<pre><code>// Extension Methods are added by adding a using to the namespace
using ProjectName.Extensions;

Orientation.North.ToMagicNumber();
</code></pre>
And here is the code:
<pre><code>namespace ProjectName.Extensions
{
 public static class OrientationExtensions 
 {
 public static int ToMagicNumber(this Orientation orientation) =&gt; oritentation switch
 {
 case None =&gt; -1,
 case North =&gt; 0,
 case East =&gt; 1,
 case South =&gt; 2,
 case West =&gt; 3,
 _ =&gt; throw new ArgumentOutOfRangeException(nameof(orientation), $&quot;Not expected orientation value: {orientation}&quot;)
 };
 }
}
</code></pre>

In C#, is it possible to decorate an Enum type with an attribute or do something else to specify what the default value should be, without having the change the values? The numbers required might be set in stone for whatever reason, and it'd be handy to still have control over the default.

<pre><code>enum Orientation
{
 None = -1,
 North = 0,
 East = 1,
 South = 2,
 West = 3
}

Orientation o; // Is 'North' by default.
</code></pre>

Choosing the default value of an Enum type without having to change values

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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在C#中，有没有可能用属性修饰枚举类型，或者做其他事情来指定默认值应该是什么，而不需要更改这些值？无论出于什么原因，所需的数字可能都是板上钉钉的，如果仍然可以控制缺省值，那将是非常方便的。enum Orientation{    None = -1,    North = 0,    East = 1,    Sout...

问在不更改值的情况下选择枚举类型的默认值
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