Fetching a Nullable<Enum> value.

I would like to retrieve an already persisted enum value from the database. Is there a problem with the following test code?

using System;
using System.IO;

using NUnit.Framework;

using SQLite;

namespace Tests
{
    enum Foo
    {
        Bar = 1,
        Baz = 2
    }

    class FooEntity
    {
        [PrimaryKey, AutoIncrement]
        public int? ID { get; set; }
        public Foo? FooEnum { get; set; }
    }

    [TestFixture]
    public class NullableEnumFetchingTests
    {
        [Test]
        public void NullableEnumStorageTest ()
        {
            SQLiteDatabase db = new SQLiteDatabase (DatabaseFilePath ("NullableEnumStorageTests.db3"));
            db.CreateTable<FooEntity> ();

            FooEntity e1 = new FooEntity {
                FooEnum = Foo.Baz
            };

            db.Insert (e1);

            FooEntity e2 = db.Get<FooEntity> (e1.ID);
            Assert.AreEqual (e1.FooEnum, e2.FooEnum);
        }

        public static string DatabaseFilePath (string sqliteFilename)
        {
            if (sqliteFilename == null)
                throw new ArgumentNullException ("sqliteFilename"); 
            //
            // Source: http://docs.xamarin.com/ios/Guides/Application_Fundamentals/Working_with_the_File_System
            // We need to put in /Library/ on iOS5.1 to meet Apple's iCloud terms
            // (they don't want non-user-generated data in Documents)
            string documentsPath = Environment.GetFolderPath (Environment.SpecialFolder.Personal); // Documents folder
            string libraryPath = Path.Combine (documentsPath, "../Library/"); // Library folder
            var path = Path.Combine (libraryPath, sqliteFilename);

            return path;    
        }
    }
}

Right after inserting an instance of my FooEntity into the database I was able to take the next screenshot.

But when trying to retrieve the inserted instance back, I am facing the next exception:

[FAIL] NullableEnumStorageTest : System.ArgumentException : failed to convert parameters
2013-01-30 18:41:28.979 Tests[54480:c07]          at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x000eb] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System.Reflection/MonoMethod.cs:242 
2013-01-30 18:41:28.980 Tests[54480:c07]          at System.Reflection.MonoProperty.SetValue (System.Object obj, System.Object value, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] index, System.Globalization.CultureInfo culture) [0x00064] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System.Reflection/MonoProperty.cs:353 
2013-01-30 18:41:28.981 Tests[54480:c07]          at System.Reflection.PropertyInfo.SetValue (System.Object obj, System.Object value, System.Object[] index) [0x00000] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System.Reflection/PropertyInfo.cs:93 
2013-01-30 18:41:28.981 Tests[54480:c07]          at SQLite.TableMapping+Column.SetValue (System.Object obj, System.Object val) [0x00000] in /Users/SQLite.cs:1609 
2013-01-30 18:41:28.982 Tests[54480:c07]          at SQLite.SQLiteCommand+<ExecuteDeferredQuery>c__Iterator0`1[A.a.Tests.DAL.FooEntity].MoveNext () [0x0016f] in /Users/SQLite.cs:1820 
2013-01-30 18:41:28.982 Tests[54480:c07]          at System.Collections.Generic.List`1[A.a.Tests.DAL.FooEntity].AddEnumerable (IEnumerable`1 enumerable) [0x0001a] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System.Collections.Generic/List.cs:127 
2013-01-30 18:41:28.983 Tests[54480:c07]          at System.Collections.Generic.List`1[A.a.Tests.DAL.FooEntity]..ctor (IEnumerable`1 collection) [0x0002f] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System.Collections.Generic/List.cs:64 
2013-01-30 18:41:28.983 Tests[54480:c07]          at System.Linq.Enumerable.ToList[FooEntity] (IEnumerable`1 source) [0x00006] in /Developer/MonoTouch/Source/mono/mcs/class/System.Core/System.Linq/Enumerable.cs:2931 
2013-01-30 18:41:28.984 Tests[54480:c07]          at SQLite.SQLiteCommand.ExecuteQuery[FooEntity] () [0x00000] in /Users/SQLite.cs:1773 
2013-01-30 18:41:28.984 Tests[54480:c07]          at SQLite.SQLiteConnection.Query[FooEntity] (System.String query, System.Object[] args) [0x00009] in /Users/SQLite.cs:531 
2013-01-30 18:41:28.985 Tests[54480:c07]          at SQLite.SQLiteConnection.Get[FooEntity] (System.Object pk) [0x00011] in /Users/SQLite.cs:638 
2013-01-30 18:41:28.986 Tests[54480:c07]          at A.a.Tests.DAL.NullableEnumFetchingTests.NullableEnumStorageTest () [0x00034] in /Users/NullableEnumFetchingTests.cs:44 
2013-01-30 18:41:28.986 Tests[54480:c07]          at (wrapper managed-to-native) System.Reflection.MonoMethod:InternalInvoke (System.Reflection.MonoMethod,object,object[],System.Exception&)
2013-01-30 18:41:28.987 Tests[54480:c07]          at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x000c0] in /Developer/MonoTouch/Source/mono/mcs/class/corlib/System.Reflection/MonoMethod.cs:228 

I have tried to fix this issue by following the next link: http://code.google.com/p/sqlite-net/issues/detail?id=47

But it isn’t compatible with silverlight and monotouch.

May some of you folks help me with this issue? Thanks in advance.

[fedemkr]

As a workaround, we could just ignore the nullable enum and add another property that wraps the nullable one as a short or whatever type the enum can be casted to:

        [Ignore]
        public Priority? Priority { get; set; }

        public short PrioritySQL
        {
            get
            {
                return (short?)this.Priority ?? -1;
            }
            set
            {
                this.Priority = value == -1 ? (Priority?)null : (Priority)value;
            }
        }

Hope this helps!

[chernihiv]

Hi guys, the issue had been created 3-4 years ago but I found this bug yesterday. Has it been fixed?

I’ve got entity with ‘ChecklistResultStatus?’ prop. There are a lot of data within table with real values (ChecklistResultStatus: 1,2,3,4, ect), but I can’t load it. Additional information: Object of type 'System.Int32' cannot be converted to type 'System.Nullable1[Enums.ChecklistResultStatus]'.

Is there any estimates when this bug is going to be fixed?