Enum and generics
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I have a generic method which looks for a specific attribute and returns value of "Text" property. My attribute is named "DetailsAttribute". Here is my generic method
public static string GetDescription<EnumType>(EnumType enumType) {
string description = string.Empty; Type type = enumType.GetType(); if (type != null) { // Getting filed info FieldInfo info = type.GetField(enumType.ToString()); if (info != null) { // getting the attributes DetailsAttribute\[\] attributes = info.GetCustomAttributes(typeof(DetailsAttribute), false) as DetailsAttribute\[\]; if (attributes != null && attributes.Length > 0) description = attributes\[0\].Text; } } return description;}
This works fine. But I am looking for applying a constraint to the generic parameter "enumType" which should allow only enum types. I am not able to write something like
public static string GetDescription<EnumType>(EnumType enumType) : where enumType : enum // error
How can I set such kind of restriction ? Also is there any better method than what I provided to retrieve attribute values from fields ? any help would be appreciated.
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Maybe you should check it by yourself. Just like this: public static string GetDescription(EnumType enumType) { string description = string.Empty; Type type = enumType.GetType(); Type typParent=type.BaseType; bool blIsEnum=false; while(typParent!=null) { if(typParent==typeof(System.Enum)) { blIsEnum=true; break; } typParent=typParent.BaseType; } if(blIsEnum==false) { throw new Exception("Haha,game over!^_^"); } ......
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N a v a n e e t h wrote:
How can I set such kind of restriction ?
You cant. Best will be to have
where EnumType : structand have a check inside the method.xacc.ide - now with TabsToSpaces support
IronScheme - 1.0 alpha 4a out now (29 May 2008)Yeah, I guessed it. Thanks leppie. Do you think there is any better method to take the attribute value other than what I did ?
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Maybe you should check it by yourself. Just like this: public static string GetDescription(EnumType enumType) { string description = string.Empty; Type type = enumType.GetType(); Type typParent=type.BaseType; bool blIsEnum=false; while(typParent!=null) { if(typParent==typeof(System.Enum)) { blIsEnum=true; break; } typParent=typParent.BaseType; } if(blIsEnum==false) { throw new Exception("Haha,game over!^_^"); } ......
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Thanks.
xibeifeijian wrote:
Type type = enumType.GetType(); Type typParent=type.BaseType; bool blIsEnum=false; while(typParent!=null)
Why not make it simple like
if (enumType.GetType() != typeof(System.Enum))
throw new InvalidOperationException("An enum is expected");or am I missing something ?
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Thanks.
xibeifeijian wrote:
Type type = enumType.GetType(); Type typParent=type.BaseType; bool blIsEnum=false; while(typParent!=null)
Why not make it simple like
if (enumType.GetType() != typeof(System.Enum))
throw new InvalidOperationException("An enum is expected");or am I missing something ?
All C# applications should call Application.Quit(); in the beginning to avoid any .NET problems.- Unclyclopedia How to use google | Ask smart questions
Ha,Sorry,my error. As the enum type cann't inherit,so you can judge it in this way: if (enumType.GetType().BaseType != typeof(System.Enum)) You must use basetype to judge them,because the son type won't equals the parent type.System.Enum is a root type for all the enum types.
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Thanks.
xibeifeijian wrote:
Type type = enumType.GetType(); Type typParent=type.BaseType; bool blIsEnum=false; while(typParent!=null)
Why not make it simple like
if (enumType.GetType() != typeof(System.Enum))
throw new InvalidOperationException("An enum is expected");or am I missing something ?
All C# applications should call Application.Quit(); in the beginning to avoid any .NET problems.- Unclyclopedia How to use google | Ask smart questions
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Ha,Sorry,my error. As the enum type cann't inherit,so you can judge it in this way: if (enumType.GetType().BaseType != typeof(System.Enum)) You must use basetype to judge them,because the son type won't equals the parent type.System.Enum is a root type for all the enum types.
:^):^):^):^):^):^):^):^):^):^):^):^) :^):rose::rose::rose::rose::rose:¦¦?¦?¦¦ :^):rose::^):^):^):^)¦?????¦ :^):rose::^):^):^):^)¦¦?¦?¦¦ :^):rose::^):^):^):^)¦?????¦ :^):rose::rose::rose::rose::rose:¦¦?¦?¦¦ :^):^):^):^):^):^):^):^):^):^):^):^)
Ya.. BaseType is required. Thanks :)
All C# applications should call Application.Quit(); in the beginning to avoid any .NET problems.- Unclyclopedia How to use google | Ask smart questions
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How about:
enumType is Enum... :doh: You guys certainly like to do things the hard way! ;Pxacc.ide - now with TabsToSpaces support
IronScheme - 1.0 alpha 4a out now (29 May 2008)leppie wrote:
enumType is Enum
Looks simple, but I cannot make it working. AFAIK,
BaseTypechecking is required. When you useis, it throws exception for enum types too.All C# applications should call Application.Quit(); in the beginning to avoid any .NET problems.- Unclyclopedia How to use google | Ask smart questions
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leppie wrote:
enumType is Enum
Looks simple, but I cannot make it working. AFAIK,
BaseTypechecking is required. When you useis, it throws exception for enum types too.All C# applications should call Application.Quit(); in the beginning to avoid any .NET problems.- Unclyclopedia How to use google | Ask smart questions
N a v a n e e t h wrote:
Looks simple, but I cannot make it working. AFAIK, BaseType checking is required. When you use is, it throws exception for enum types too.
Then you are doing something wrong! The following prints 'Friday':
object f = DayOfWeek.Friday;
if (f is Enum)
{
Console.WriteLine(f);
}
else
{
Console.WriteLine("Not enum");
}xacc.ide - now with TabsToSpaces support
IronScheme - 1.0 alpha 4a out now (29 May 2008) -
I have a generic method which looks for a specific attribute and returns value of "Text" property. My attribute is named "DetailsAttribute". Here is my generic method
public static string GetDescription<EnumType>(EnumType enumType) {
string description = string.Empty; Type type = enumType.GetType(); if (type != null) { // Getting filed info FieldInfo info = type.GetField(enumType.ToString()); if (info != null) { // getting the attributes DetailsAttribute\[\] attributes = info.GetCustomAttributes(typeof(DetailsAttribute), false) as DetailsAttribute\[\]; if (attributes != null && attributes.Length > 0) description = attributes\[0\].Text; } } return description;}
This works fine. But I am looking for applying a constraint to the generic parameter "enumType" which should allow only enum types. I am not able to write something like
public static string GetDescription<EnumType>(EnumType enumType) : where enumType : enum // error
How can I set such kind of restriction ? Also is there any better method than what I provided to retrieve attribute values from fields ? any help would be appreciated.
All C# applications should call Application.Quit(); in the beginning to avoid any .NET problems.- Unclyclopedia How to use google | Ask smart questions
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Haha ,this is the best way ! :)
:^):^):^):^):^):^):^):^):^):^):^):^) :^):rose::rose::rose::rose::rose:¦¦?¦?¦¦ :^):rose::^):^):^):^)¦?????¦ :^):rose::^):^):^):^)¦¦?¦?¦¦ :^):rose::^):^):^):^)¦?????¦ :^):rose::rose::rose::rose::rose:¦¦?¦?¦¦ :^):^):^):^):^):^):^):^):^):^):^):^)
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PIEBALDconsult wrote:
Does no one read my articles?
Sorry, I just missed it.
PIEBALDconsult wrote:
I suspect that all that checking for null in your example is needless.
I am not getting you fully. Are you saying that the methods I used to get "FieldInfo", attributes will never return NULL ?
All C# applications should call Application.Quit(); in the beginning to avoid any .NET problems.- Unclyclopedia How to use google | Ask smart questions
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I have a generic method which looks for a specific attribute and returns value of "Text" property. My attribute is named "DetailsAttribute". Here is my generic method
public static string GetDescription<EnumType>(EnumType enumType) {
string description = string.Empty; Type type = enumType.GetType(); if (type != null) { // Getting filed info FieldInfo info = type.GetField(enumType.ToString()); if (info != null) { // getting the attributes DetailsAttribute\[\] attributes = info.GetCustomAttributes(typeof(DetailsAttribute), false) as DetailsAttribute\[\]; if (attributes != null && attributes.Length > 0) description = attributes\[0\].Text; } } return description;}
This works fine. But I am looking for applying a constraint to the generic parameter "enumType" which should allow only enum types. I am not able to write something like
public static string GetDescription<EnumType>(EnumType enumType) : where enumType : enum // error
How can I set such kind of restriction ? Also is there any better method than what I provided to retrieve attribute values from fields ? any help would be appreciated.
All C# applications should call Application.Quit(); in the beginning to avoid any .NET problems.- Unclyclopedia How to use google | Ask smart questions
You can't apply a generic constraint on an enum type. The best you can get is struct. Also, take a look at this article[^] for a way to work with enums and a description attribute.
Scott Dorman
Microsoft® MVP - Visual C# | MCPD President - Tampa Bay IASA [Blog][Articles][Forum Guidelines]
Hey, hey, hey. Don't be mean. We don't have to be mean because, remember, no matter where you go, there you are. - Buckaroo Banzai
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PIEBALDconsult wrote:
Does no one read my articles?
Hmmm...I missed that one somehow. Interesting approach to things. Did you see my article[^]? I have a similar GetDescription method.
Scott Dorman
Microsoft® MVP - Visual C# | MCPD President - Tampa Bay IASA [Blog][Articles][Forum Guidelines]
Hey, hey, hey. Don't be mean. We don't have to be mean because, remember, no matter where you go, there you are. - Buckaroo Banzai
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PIEBALDconsult wrote:
Does no one read my articles?
Sorry, I just missed it.
PIEBALDconsult wrote:
I suspect that all that checking for null in your example is needless.
I am not getting you fully. Are you saying that the methods I used to get "FieldInfo", attributes will never return NULL ?
All C# applications should call Application.Quit(); in the beginning to avoid any .NET problems.- Unclyclopedia How to use google | Ask smart questions
Correct. GetType() won't and GetCustomAttributes won't, GetField won't because you're passing in a known field name (in this case).
modified on Tuesday, July 8, 2008 12:41 AM
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PIEBALDconsult wrote:
Does no one read my articles?
Hmmm...I missed that one somehow. Interesting approach to things. Did you see my article[^]? I have a similar GetDescription method.
Scott Dorman
Microsoft® MVP - Visual C# | MCPD President - Tampa Bay IASA [Blog][Articles][Forum Guidelines]
Hey, hey, hey. Don't be mean. We don't have to be mean because, remember, no matter where you go, there you are. - Buckaroo Banzai
I probably did, I definitely remember the picture of someone blocking the Green Monster.
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I have a generic method which looks for a specific attribute and returns value of "Text" property. My attribute is named "DetailsAttribute". Here is my generic method
public static string GetDescription<EnumType>(EnumType enumType) {
string description = string.Empty; Type type = enumType.GetType(); if (type != null) { // Getting filed info FieldInfo info = type.GetField(enumType.ToString()); if (info != null) { // getting the attributes DetailsAttribute\[\] attributes = info.GetCustomAttributes(typeof(DetailsAttribute), false) as DetailsAttribute\[\]; if (attributes != null && attributes.Length > 0) description = attributes\[0\].Text; } } return description;}
This works fine. But I am looking for applying a constraint to the generic parameter "enumType" which should allow only enum types. I am not able to write something like
public static string GetDescription<EnumType>(EnumType enumType) : where enumType : enum // error
How can I set such kind of restriction ? Also is there any better method than what I provided to retrieve attribute values from fields ? any help would be appreciated.
All C# applications should call Application.Quit(); in the beginning to avoid any .NET problems.- Unclyclopedia How to use google | Ask smart questions
Oh, and... a few months ago I asked about it on MSDN and Jon Skeet said he'd ask whether or not an enum constraint might be in the future, he later reported... "maybe". I suspect there are a lot more important things concerning them. I think maybe we should start a letter campaign.
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Correct. GetType() won't and GetCustomAttributes won't, GetField won't because you're passing in a known field name (in this case).
modified on Tuesday, July 8, 2008 12:41 AM
Thanks. I will remove the NULL checking. Thanks
All C# applications should call Application.Quit(); in the beginning to avoid any .NET problems.- Unclyclopedia How to use google | Ask smart questions
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You can't apply a generic constraint on an enum type. The best you can get is struct. Also, take a look at this article[^] for a way to work with enums and a description attribute.
Scott Dorman
Microsoft® MVP - Visual C# | MCPD President - Tampa Bay IASA [Blog][Articles][Forum Guidelines]
Hey, hey, hey. Don't be mean. We don't have to be mean because, remember, no matter where you go, there you are. - Buckaroo Banzai
Scott, Thanks. I figured it out. Great article though
All C# applications should call Application.Quit(); in the beginning to avoid any .NET problems.- Unclyclopedia How to use google | Ask smart questions
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Oh, and... a few months ago I asked about it on MSDN and Jon Skeet said he'd ask whether or not an enum constraint might be in the future, he later reported... "maybe". I suspect there are a lot more important things concerning them. I think maybe we should start a letter campaign.
PIEBALDconsult wrote:
I asked about it on MSDN and Jon Skeet said he'd ask whether or not an enum constraint might be in the future,
Ohh, so what could replace enums ? Jon Skeet - I love that guy. He got indepth knowledge on the subject and very helping too. He has a book out "C# in Depth". I got a copy, it's worth reading.
All C# applications should call Application.Quit(); in the beginning to avoid any .NET problems.- Unclyclopedia How to use google | Ask smart questions
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Scott, Thanks. I figured it out. Great article though
All C# applications should call Application.Quit(); in the beginning to avoid any .NET problems.- Unclyclopedia How to use google | Ask smart questions
N a v a n e e t h wrote:
Thanks. I figured it out. Great article though
You're welcome. Glad you liked the article.
Scott Dorman
Microsoft® MVP - Visual C# | MCPD President - Tampa Bay IASA [Blog][Articles][Forum Guidelines]
Hey, hey, hey. Don't be mean. We don't have to be mean because, remember, no matter where you go, there you are. - Buckaroo Banzai