Linq to SQL With Enum On Null Field [MODIFIED]
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I have a table that store person data. There are NamePrefix and NameSuffix columns in the data. Both are nullable. Here is the Persons table
CREATE TABLE [dbo].[Persons]
(
Id INT IDENTITY(1,1) PRIMARY KEY NOT NULL,
RemoteId UNIQUEIDENTIFIER NOT NULL,
ClientRepId INT NULL FOREIGN KEY (ClientRepId) REFERENCES Persons(Id),
SupervisorId INT NULL FOREIGN KEY (SupervisorId) REFERENCES Persons(Id),
PersonType INT NOT NULL,
Prefix INT NULL,
FirstName VARCHAR(MAX),
LastName VARCHAR(MAX),
NickName VARCHAR(MAX),
Suffix INT NULL,
Title VARCHAR(MAX)
)Here is the PersonEntity
namespace CLOI.Entities
{
public class PersonEntity : _EntityBase
{
private PersonType _PersonType;
public PersonType PersonType
{
get { return _PersonType; }
set
{
SetProperty("PersonType", ref _PersonType, value);
}
}private NamePrefix \_Prefix; public NamePrefix Prefix { get { return \_Prefix; } set { SetProperty("Prefix", ref \_Prefix, value); } } private string \_FirstName; public string FirstName { get { return \_FirstName; } set { SetProperty("FirstName", ref \_FirstName, value); } } private string \_LastName; public string LastName { get { return \_LastName; } set { SetProperty("LastName", ref \_LastName, value); } } private string \_NickName; public string NickName { get { return \_NickName; } set { SetProperty("NickName", ref \_NickName, value); } } private NameSuffix \_Suffix; public NameSuffix Suffix { get { return \_Suffix; } set { SetProperty("Suffix", ref \_Suffix, value); } } private string \_Title; public string Title { get { return \_Title; } set { SetProperty("Title", ref \_Title, value); } } public string FullName { get { return $"{FirstName} {LastName}"; } } private int \_ClientRepId; public int ClientRepId { get { return \_ClientRepId; } set { SetProperty("ClientRepId", ref \_ClientRepId, value); } } }}
I'm trying to get this to work:
results = (from p in dc.Persons
select new PersonEntity
{
RemoteId = p.RemoteId,
ClientRepId = p.ClientRepId ?? 0,
SupervisorId = p.SupervisorId ?? 0,An Enum on a nullable field? A null value cannot be cast to an enum value. Enums are value types, not reference types, and they must have a value. They cannot be null.
Asking questions is a skill CodeProject Forum Guidelines Google: C# How to debug code Seriously, go read these articles.
Dave Kreskowiak -
It's going to depend on the definition of the
NamePrefixandNameSuffixclasses, as well as thep.Prefixproperty. I'd hope that the two classes are derived from whatever classPrefixis, but you've probably got that covered. Check thatPrefixis also nullable."I have no idea what I did, but I'm taking full credit for it." - ThisOldTony "Common sense is so rare these days, it should be classified as a super power" - Random T-shirt AntiTwitter: @DalekDave is now a follower!
I updated my original post to show the SQL table and the Person entity, as well as my updated Linq-To-SQL quert in my DAL. PrefixType and SuffixType are both enums. The Prefix and Suffix columns in the table are nullable. The PersonEntity has both PrefixType and SuffixType enum properties. But since the underlying data for both is null, I'd like to set the enum to PrefxType.None and SuffixType.None. So I'm trying to coerce the enum property to None for null data values. In this line here, p.Prefix is a null int.
Prefix = (NamePrefix)p.Prefix ?? NamePrefix.None
Thanks
If it's not broken, fix it until it is. Everything makes sense in someone's mind. Ya can't fix stupid.
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An Enum on a nullable field? A null value cannot be cast to an enum value. Enums are value types, not reference types, and they must have a value. They cannot be null.
Asking questions is a skill CodeProject Forum Guidelines Google: C# How to debug code Seriously, go read these articles.
Dave KreskowiakPlease see my reply to Griff. Thanks
If it's not broken, fix it until it is. Everything makes sense in someone's mind. Ya can't fix stupid.
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I updated my original post to show the SQL table and the Person entity, as well as my updated Linq-To-SQL quert in my DAL. PrefixType and SuffixType are both enums. The Prefix and Suffix columns in the table are nullable. The PersonEntity has both PrefixType and SuffixType enum properties. But since the underlying data for both is null, I'd like to set the enum to PrefxType.None and SuffixType.None. So I'm trying to coerce the enum property to None for null data values. In this line here, p.Prefix is a null int.
Prefix = (NamePrefix)p.Prefix ?? NamePrefix.None
Thanks
If it's not broken, fix it until it is. Everything makes sense in someone's mind. Ya can't fix stupid.
The way I'd fix this is to make those column NOT nullable. The "None" value would be 0. But, since I don't know the business rules, you may or may not get away with this.
Asking questions is a skill CodeProject Forum Guidelines Google: C# How to debug code Seriously, go read these articles.
Dave Kreskowiak -
I updated my original post to show the SQL table and the Person entity, as well as my updated Linq-To-SQL quert in my DAL. PrefixType and SuffixType are both enums. The Prefix and Suffix columns in the table are nullable. The PersonEntity has both PrefixType and SuffixType enum properties. But since the underlying data for both is null, I'd like to set the enum to PrefxType.None and SuffixType.None. So I'm trying to coerce the enum property to None for null data values. In this line here, p.Prefix is a null int.
Prefix = (NamePrefix)p.Prefix ?? NamePrefix.None
Thanks
If it's not broken, fix it until it is. Everything makes sense in someone's mind. Ya can't fix stupid.
And there is your problem:
enumis not a nullable type (it's syntactical sugar for a boring oldint) so it can't be tested using the??operator - hence the error message. I'd strongly suggest that your data source is the problem, and that that shouldn't be capable of returning null value in that field - but if you cast it to a nullable int, you should be able to use that with the??operator to return anenum. I haven't tested it - I'm on a tablet and coding becomes a true PITA without a proper KB and mouse! :laugh:"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony "Common sense is so rare these days, it should be classified as a super power" - Random T-shirt AntiTwitter: @DalekDave is now a follower!
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The way I'd fix this is to make those column NOT nullable. The "None" value would be 0. But, since I don't know the business rules, you may or may not get away with this.
Asking questions is a skill CodeProject Forum Guidelines Google: C# How to debug code Seriously, go read these articles.
Dave KreskowiakYou're right. At the time I didn't have the 'None' enum, but it makes sense. Much better. Thanks
If it's not broken, fix it until it is. Everything makes sense in someone's mind. Ya can't fix stupid.
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And there is your problem:
enumis not a nullable type (it's syntactical sugar for a boring oldint) so it can't be tested using the??operator - hence the error message. I'd strongly suggest that your data source is the problem, and that that shouldn't be capable of returning null value in that field - but if you cast it to a nullable int, you should be able to use that with the??operator to return anenum. I haven't tested it - I'm on a tablet and coding becomes a true PITA without a proper KB and mouse! :laugh:"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony "Common sense is so rare these days, it should be classified as a super power" - Random T-shirt AntiTwitter: @DalekDave is now a follower!
I just had a thought and tested it. This works
results = (from p in dc.Persons
select new PersonEntity
{
RemoteId = p.RemoteId,
ClientRepId = p.ClientRepId ?? 0,
SupervisorId = p.SupervisorId ?? 0,
PersonType = (PersonType)p.PersonType,
Prefix = p.Prefix == null ? NamePrefix.None : (NamePrefix)p.Prefix,
FirstName = p.FirstName,
LastName = p.LastName,
NickName = p.NickName,
Suffix = p.Suffix == null ? NameSuffix.None : (NameSuffix)p.Suffix,
Title = p.Title,
CreatedById = p.CreatedById,
CreatedDT = p.CreatedDT,
LastModifiedById = p.Id,
LastModifiedDT = p.ModifiedByDT.Value,
DeletedById = p.DeletedById,
DeletedDT = p.DeletedByDT.Value
}).Where(predicate).ToList();If it's not broken, fix it until it is. Everything makes sense in someone's mind. Ya can't fix stupid.
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I just had a thought and tested it. This works
results = (from p in dc.Persons
select new PersonEntity
{
RemoteId = p.RemoteId,
ClientRepId = p.ClientRepId ?? 0,
SupervisorId = p.SupervisorId ?? 0,
PersonType = (PersonType)p.PersonType,
Prefix = p.Prefix == null ? NamePrefix.None : (NamePrefix)p.Prefix,
FirstName = p.FirstName,
LastName = p.LastName,
NickName = p.NickName,
Suffix = p.Suffix == null ? NameSuffix.None : (NameSuffix)p.Suffix,
Title = p.Title,
CreatedById = p.CreatedById,
CreatedDT = p.CreatedDT,
LastModifiedById = p.Id,
LastModifiedDT = p.ModifiedByDT.Value,
DeletedById = p.DeletedById,
DeletedDT = p.DeletedByDT.Value
}).Where(predicate).ToList();If it's not broken, fix it until it is. Everything makes sense in someone's mind. Ya can't fix stupid.
Just curious; How did
Kevin Marois wrote:
CreatedById = p.CreatedById, CreatedDT = p.CreatedDT, LastModifiedById = p.Id, LastModifiedDT = p.ModifiedByDT.Value, DeletedById = p.DeletedById, DeletedDT = p.DeletedByDT.Value
affect the answer?
Bastard Programmer from Hell :suss: "If you just follow the bacon Eddy, wherever it leads you, then you won't have to think about politics." -- Some Bell.
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Just curious; How did
Kevin Marois wrote:
CreatedById = p.CreatedById, CreatedDT = p.CreatedDT, LastModifiedById = p.Id, LastModifiedDT = p.ModifiedByDT.Value, DeletedById = p.DeletedById, DeletedDT = p.DeletedByDT.Value
affect the answer?
Bastard Programmer from Hell :suss: "If you just follow the bacon Eddy, wherever it leads you, then you won't have to think about politics." -- Some Bell.
It didn't. I had ommitted those properties before for brevity
If it's not broken, fix it until it is. Everything makes sense in someone's mind. Ya can't fix stupid.
-
I have a table that store person data. There are NamePrefix and NameSuffix columns in the data. Both are nullable. Here is the Persons table
CREATE TABLE [dbo].[Persons]
(
Id INT IDENTITY(1,1) PRIMARY KEY NOT NULL,
RemoteId UNIQUEIDENTIFIER NOT NULL,
ClientRepId INT NULL FOREIGN KEY (ClientRepId) REFERENCES Persons(Id),
SupervisorId INT NULL FOREIGN KEY (SupervisorId) REFERENCES Persons(Id),
PersonType INT NOT NULL,
Prefix INT NULL,
FirstName VARCHAR(MAX),
LastName VARCHAR(MAX),
NickName VARCHAR(MAX),
Suffix INT NULL,
Title VARCHAR(MAX)
)Here is the PersonEntity
namespace CLOI.Entities
{
public class PersonEntity : _EntityBase
{
private PersonType _PersonType;
public PersonType PersonType
{
get { return _PersonType; }
set
{
SetProperty("PersonType", ref _PersonType, value);
}
}private NamePrefix \_Prefix; public NamePrefix Prefix { get { return \_Prefix; } set { SetProperty("Prefix", ref \_Prefix, value); } } private string \_FirstName; public string FirstName { get { return \_FirstName; } set { SetProperty("FirstName", ref \_FirstName, value); } } private string \_LastName; public string LastName { get { return \_LastName; } set { SetProperty("LastName", ref \_LastName, value); } } private string \_NickName; public string NickName { get { return \_NickName; } set { SetProperty("NickName", ref \_NickName, value); } } private NameSuffix \_Suffix; public NameSuffix Suffix { get { return \_Suffix; } set { SetProperty("Suffix", ref \_Suffix, value); } } private string \_Title; public string Title { get { return \_Title; } set { SetProperty("Title", ref \_Title, value); } } public string FullName { get { return $"{FirstName} {LastName}"; } } private int \_ClientRepId; public int ClientRepId { get { return \_ClientRepId; } set { SetProperty("ClientRepId", ref \_ClientRepId, value); } } }}
I'm trying to get this to work:
results = (from p in dc.Persons
select new PersonEntity
{
RemoteId = p.RemoteId,
ClientRepId = p.ClientRepId ?? 0,
SupervisorId = p.SupervisorId ?? 0,Depending on how well the ORM works, you may be able to use:
Prefix = (NamePrefix?)p.Prefix ?? NamePrefix.None,
NB: Using an enum for a name prefix or suffix seems like a bad idea. What happens when your users try to add a person whose prefix / suffix doesn't exist in your list? Are you going to make that person wait while you recompile your application? I'd suggest either using a lookup table, or just free-text values.
"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer
